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docs: power: convert docs to ReST and rename to *.rst

Browse Source 
Convert the PM documents to ReST, in order to allow them to
build with Sphinx.

The conversion is actually:
  - add blank lines and indentation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
This commit is contained in:
Mauro Carvalho Chehab 2019-06-13 07:10:36 -03:00 committed by Bjorn Helgaas
parent 9595aee2a3
commit 151f4e2bdc
51 changed files with 2127 additions and 1706 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/ABI/testing/sysfs-class-powercap
View File

@ -5,7 +5,7 @@ Contact: linux-pm@vger.kernel.org
Description:
The powercap/ class sub directory belongs to the power cap
subsystem. Refer to
Documentation/power/powercap/powercap.txt for details.
Documentation/power/powercap/powercap.rst for details.
What: /sys/class/powercap/<control type>
Date: September 2013

6
Documentation/admin-guide/kernel-parameters.txt
View File

@ -13,7 +13,7 @@
For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
are available
See also Documentation/power/runtime_pm.txt, pci=noacpi
See also Documentation/power/runtime_pm.rst, pci=noacpi
acpi_apic_instance= [ACPI, IOAPIC]
Format: <int>
@ -223,7 +223,7 @@
acpi_sleep= [HW,ACPI] Sleep options
Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
old_ordering, nonvs, sci_force_enable, nobl }
See Documentation/power/video.txt for information on
See Documentation/power/video.rst for information on
s3_bios and s3_mode.
s3_beep is for debugging; it makes the PC's speaker beep
as soon as the kernel's real-mode entry point is called.
@ -4108,7 +4108,7 @@
Specify the offset from the beginning of the partition
given by "resume=" at which the swap header is located,
in <PAGE_SIZE> units (needed only for swap files).
See Documentation/power/swsusp-and-swap-files.txt
See Documentation/power/swsusp-and-swap-files.rst
resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
read the resume files

2
Documentation/cpu-freq/core.txt
View File

@ -95,7 +95,7 @@ flags - flags of the cpufreq driver
3. CPUFreq Table Generation with Operating Performance Point (OPP)
==================================================================
For details about OPP, see Documentation/power/opp.txt
For details about OPP, see Documentation/power/opp.rst
dev_pm_opp_init_cpufreq_table -
This function provides a ready to use conversion routine to translate

6
Documentation/driver-api/pm/devices.rst
View File

@ -225,7 +225,7 @@ system-wide transition to a sleep state even though its :c:member:`runtime_auto`
flag is clear.
For more information about the runtime power management framework, refer to
:file:`Documentation/power/runtime_pm.txt`.
:file:`Documentation/power/runtime_pm.rst`.
Calling Drivers to Enter and Leave System Sleep States
@ -728,7 +728,7 @@ it into account in any way.
Devices may be defined as IRQ-safe which indicates to the PM core that their
runtime PM callbacks may be invoked with disabled interrupts (see
:file:`Documentation/power/runtime_pm.txt` for more information). If an
:file:`Documentation/power/runtime_pm.rst` for more information). If an
IRQ-safe device belongs to a PM domain, the runtime PM of the domain will be
disallowed, unless the domain itself is defined as IRQ-safe. However, it
makes sense to define a PM domain as IRQ-safe only if all the devices in it
@ -795,7 +795,7 @@ so on) and the final state of the device must reflect the "active" runtime PM
status in that case.
During system-wide resume from a sleep state it's easiest to put devices into
the full-power state, as explained in :file:`Documentation/power/runtime_pm.txt`.
the full-power state, as explained in :file:`Documentation/power/runtime_pm.rst`.
[Refer to that document for more information regarding this particular issue as
well as for information on the device runtime power management framework in
general.]

2
Documentation/driver-api/usb/power-management.rst
View File

@ -46,7 +46,7 @@ device is turned off while the system as a whole remains running, we
call it a "dynamic suspend" (also known as a "runtime suspend" or
"selective suspend"). This document concentrates mostly on how
dynamic PM is implemented in the USB subsystem, although system PM is
covered to some extent (see ``Documentation/power/*.txt`` for more
covered to some extent (see ``Documentation/power/*.rst`` for more
information about system PM).
System PM support is present only if the kernel was built with

10
Documentation/power/apm-acpi.txt → Documentation/power/apm-acpi.rst
View File

@ -1,5 +1,7 @@
============
APM or ACPI?
------------
============
If you have a relatively recent x86 mobile, desktop, or server system,
odds are it supports either Advanced Power Management (APM) or
Advanced Configuration and Power Interface (ACPI). ACPI is the newer
@ -28,5 +30,7 @@ and be sure that they are started sometime in the system boot process.
Go ahead and start both. If ACPI or APM is not available on your
system the associated daemon will exit gracefully.
apmd: http://ftp.debian.org/pool/main/a/apmd/
acpid: http://acpid.sf.net/
===== =======================================
apmd http://ftp.debian.org/pool/main/a/apmd/
acpid http://acpid.sf.net/
===== =======================================

79
Documentation/power/basic-pm-debugging.txt → Documentation/power/basic-pm-debugging.rst
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@ -1,12 +1,16 @@
=================================
Debugging hibernation and suspend
=================================
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
1. Testing hibernation (aka suspend to disk or STD)
===================================================
To check if hibernation works, you can try to hibernate in the "reboot" mode:
To check if hibernation works, you can try to hibernate in the "reboot" mode::
# echo reboot > /sys/power/disk
# echo disk > /sys/power/state
# echo reboot > /sys/power/disk
# echo disk > /sys/power/state
and the system should create a hibernation image, reboot, resume and get back to
the command prompt where you have started the transition. If that happens,
@ -15,20 +19,21 @@ test at least a couple of times in a row for confidence. [This is necessary,
because some problems only show up on a second attempt at suspending and
resuming the system.] Moreover, hibernating in the "reboot" and "shutdown"
modes causes the PM core to skip some platform-related callbacks which on ACPI
systems might be necessary to make hibernation work. Thus, if your machine fails
to hibernate or resume in the "reboot" mode, you should try the "platform" mode:
systems might be necessary to make hibernation work. Thus, if your machine
fails to hibernate or resume in the "reboot" mode, you should try the
"platform" mode::
# echo platform > /sys/power/disk
# echo disk > /sys/power/state
# echo platform > /sys/power/disk
# echo disk > /sys/power/state
which is the default and recommended mode of hibernation.
Unfortunately, the "platform" mode of hibernation does not work on some systems
with broken BIOSes. In such cases the "shutdown" mode of hibernation might
work:
work::
# echo shutdown > /sys/power/disk
# echo disk > /sys/power/state
# echo shutdown > /sys/power/disk
# echo disk > /sys/power/state
(it is similar to the "reboot" mode, but it requires you to press the power
button to make the system resume).
@ -37,6 +42,7 @@ If neither "platform" nor "shutdown" hibernation mode works, you will need to
identify what goes wrong.
a) Test modes of hibernation
----------------------------
To find out why hibernation fails on your system, you can use a special testing
facility available if the kernel is compiled with CONFIG_PM_DEBUG set. Then,
@ -44,36 +50,38 @@ there is the file /sys/power/pm_test that can be used to make the hibernation
core run in a test mode. There are 5 test modes available:
freezer
- test the freezing of processes
- test the freezing of processes
devices
- test the freezing of processes and suspending of devices
- test the freezing of processes and suspending of devices
platform
- test the freezing of processes, suspending of devices and platform
global control methods(*)
- test the freezing of processes, suspending of devices and platform
global control methods [1]_
processors
- test the freezing of processes, suspending of devices, platform
global control methods(*) and the disabling of nonboot CPUs
- test the freezing of processes, suspending of devices, platform
global control methods [1]_ and the disabling of nonboot CPUs
core
- test the freezing of processes, suspending of devices, platform global
control methods(*), the disabling of nonboot CPUs and suspending of
platform/system devices
- test the freezing of processes, suspending of devices, platform global
control methods\ [1]_, the disabling of nonboot CPUs and suspending
of platform/system devices
(*) the platform global control methods are only available on ACPI systems
.. [1]
the platform global control methods are only available on ACPI systems
and are only tested if the hibernation mode is set to "platform"
To use one of them it is necessary to write the corresponding string to
/sys/power/pm_test (eg. "devices" to test the freezing of processes and
suspending devices) and issue the standard hibernation commands. For example,
to use the "devices" test mode along with the "platform" mode of hibernation,
you should do the following:
you should do the following::
# echo devices > /sys/power/pm_test
# echo platform > /sys/power/disk
# echo disk > /sys/power/state
# echo devices > /sys/power/pm_test
# echo platform > /sys/power/disk
# echo disk > /sys/power/state
Then, the kernel will try to freeze processes, suspend devices, wait a few
seconds (5 by default, but configurable by the suspend.pm_test_delay module
@ -108,11 +116,12 @@ If the "devices" test fails, most likely there is a driver that cannot suspend
or resume its device (in the latter case the system may hang or become unstable
after the test, so please take that into consideration). To find this driver,
you can carry out a binary search according to the rules:
- if the test fails, unload a half of the drivers currently loaded and repeat
(that would probably involve rebooting the system, so always note what drivers
have been loaded before the test),
(that would probably involve rebooting the system, so always note what drivers
have been loaded before the test),
- if the test succeeds, load a half of the drivers you have unloaded most
recently and repeat.
recently and repeat.
Once you have found the failing driver (there can be more than just one of
them), you have to unload it every time before hibernation. In that case please
@ -146,6 +155,7 @@ indicates a serious problem that very well may be related to the hardware, but
please report it anyway.
b) Testing minimal configuration
--------------------------------
If all of the hibernation test modes work, you can boot the system with the
"init=/bin/bash" command line parameter and attempt to hibernate in the
@ -165,14 +175,15 @@ Again, if you find the offending module(s), it(they) must be unloaded every time
before hibernation, and please report the problem with it(them).
c) Using the "test_resume" hibernation option
---------------------------------------------
/sys/power/disk generally tells the kernel what to do after creating a
hibernation image. One of the available options is "test_resume" which
causes the just created image to be used for immediate restoration. Namely,
after doing:
after doing::
# echo test_resume > /sys/power/disk
# echo disk > /sys/power/state
# echo test_resume > /sys/power/disk
# echo disk > /sys/power/state
a hibernation image will be created and a resume from it will be triggered
immediately without involving the platform firmware in any way.
@ -190,6 +201,7 @@ to resume may be related to the differences between the restore and image
kernels.
d) Advanced debugging
---------------------
In case that hibernation does not work on your system even in the minimal
configuration and compiling more drivers as modules is not practical or some
@ -200,9 +212,10 @@ kernel messages using the serial console. This may provide you with some
information about the reasons of the suspend (resume) failure. Alternatively,
it may be possible to use a FireWire port for debugging with firescope
(http://v3.sk/~lkundrak/firescope/). On x86 it is also possible to
use the PM_TRACE mechanism documented in Documentation/power/s2ram.txt .
use the PM_TRACE mechanism documented in Documentation/power/s2ram.rst .
2. Testing suspend to RAM (STR)
===============================
To verify that the STR works, it is generally more convenient to use the s2ram
tool available from http://suspend.sf.net and documented at
@ -230,7 +243,8 @@ you will have to unload them every time before an STR transition (ie. before
you run s2ram), and please report the problems with them.
There is a debugfs entry which shows the suspend to RAM statistics. Here is an
example of its output.
example of its output::
# mount -t debugfs none /sys/kernel/debug
# cat /sys/kernel/debug/suspend_stats
success: 20
@ -248,6 +262,7 @@ example of its output.
-16
last_failed_step: suspend
suspend
Field success means the success number of suspend to RAM, and field fail means
the failure number. Others are the failure number of different steps of suspend
to RAM. suspend_stats just lists the last 2 failed devices, error number and

101
Documentation/power/charger-manager.txt → Documentation/power/charger-manager.rst
View File

@ -1,4 +1,7 @@
===============
Charger Manager
===============
(C) 2011 MyungJoo Ham <myungjoo.ham@samsung.com>, GPL
Charger Manager provides in-kernel battery charger management that
@ -55,41 +58,39 @@ Charger Manager supports the following:
notification to users with UEVENT.
2. Global Charger-Manager Data related with suspend_again
========================================================
=========================================================
In order to setup Charger Manager with suspend-again feature
(in-suspend monitoring), the user should provide charger_global_desc
with setup_charger_manager(struct charger_global_desc *).
with setup_charger_manager(`struct charger_global_desc *`).
This charger_global_desc data for in-suspend monitoring is global
as the name suggests. Thus, the user needs to provide only once even
if there are multiple batteries. If there are multiple batteries, the
multiple instances of Charger Manager share the same charger_global_desc
and it will manage in-suspend monitoring for all instances of Charger Manager.
The user needs to provide all the three entries properly in order to activate
in-suspend monitoring:
The user needs to provide all the three entries to `struct charger_global_desc`
properly in order to activate in-suspend monitoring:
struct charger_global_desc {
char *rtc_name;
: The name of rtc (e.g., "rtc0") used to wakeup the system from
`char *rtc_name;`
The name of rtc (e.g., "rtc0") used to wakeup the system from
suspend for Charger Manager. The alarm interrupt (AIE) of the rtc
should be able to wake up the system from suspend. Charger Manager
saves and restores the alarm value and use the previously-defined
alarm if it is going to go off earlier than Charger Manager so that
Charger Manager does not interfere with previously-defined alarms.
bool (*rtc_only_wakeup)(void);
: This callback should let CM know whether
`bool (*rtc_only_wakeup)(void);`
This callback should let CM know whether
the wakeup-from-suspend is caused only by the alarm of "rtc" in the
same struct. If there is any other wakeup source triggered the
wakeup, it should return false. If the "rtc" is the only wakeup
reason, it should return true.
bool assume_timer_stops_in_suspend;
: if true, Charger Manager assumes that
`bool assume_timer_stops_in_suspend;`
if true, Charger Manager assumes that
the timer (CM uses jiffies as timer) stops during suspend. Then, CM
assumes that the suspend-duration is same as the alarm length.
};
3. How to setup suspend_again
=============================
@ -109,26 +110,28 @@ if the system was woken up by Charger Manager and the polling
=============================================
For each battery charged independently from other batteries (if a series of
batteries are charged by a single charger, they are counted as one independent
battery), an instance of Charger Manager is attached to it.
battery), an instance of Charger Manager is attached to it. The following
struct charger_desc {
struct charger_desc elements:
char *psy_name;
: The power-supply-class name of the battery. Default is
`char *psy_name;`
The power-supply-class name of the battery. Default is
"battery" if psy_name is NULL. Users can access the psy entries
at "/sys/class/power_supply/[psy_name]/".
enum polling_modes polling_mode;
: CM_POLL_DISABLE: do not poll this battery.
CM_POLL_ALWAYS: always poll this battery.
CM_POLL_EXTERNAL_POWER_ONLY: poll this battery if and only if
an external power source is attached.
CM_POLL_CHARGING_ONLY: poll this battery if and only if the
battery is being charged.
`enum polling_modes polling_mode;`
CM_POLL_DISABLE:
do not poll this battery.
CM_POLL_ALWAYS:
always poll this battery.
CM_POLL_EXTERNAL_POWER_ONLY:
poll this battery if and only if an external power
source is attached.
CM_POLL_CHARGING_ONLY:
poll this battery if and only if the battery is being charged.
unsigned int fullbatt_vchkdrop_ms;
unsigned int fullbatt_vchkdrop_uV;
: If both have non-zero values, Charger Manager will check the
`unsigned int fullbatt_vchkdrop_ms; / unsigned int fullbatt_vchkdrop_uV;`
If both have non-zero values, Charger Manager will check the
battery voltage drop fullbatt_vchkdrop_ms after the battery is fully
charged. If the voltage drop is over fullbatt_vchkdrop_uV, Charger
Manager will try to recharge the battery by disabling and enabling
@ -136,50 +139,52 @@ unsigned int fullbatt_vchkdrop_uV;
condition) is needed to be implemented with hardware interrupts from
fuel gauges or charger devices/chips.
unsigned int fullbatt_uV;
: If specified with a non-zero value, Charger Manager assumes
`unsigned int fullbatt_uV;`
If specified with a non-zero value, Charger Manager assumes
that the battery is full (capacity = 100) if the battery is not being
charged and the battery voltage is equal to or greater than
fullbatt_uV.
unsigned int polling_interval_ms;
: Required polling interval in ms. Charger Manager will poll
`unsigned int polling_interval_ms;`
Required polling interval in ms. Charger Manager will poll
this battery every polling_interval_ms or more frequently.
enum data_source battery_present;
: CM_BATTERY_PRESENT: assume that the battery exists.
CM_NO_BATTERY: assume that the battery does not exists.
CM_FUEL_GAUGE: get battery presence information from fuel gauge.
CM_CHARGER_STAT: get battery presence from chargers.
`enum data_source battery_present;`
CM_BATTERY_PRESENT:
assume that the battery exists.
CM_NO_BATTERY:
assume that the battery does not exists.
CM_FUEL_GAUGE:
get battery presence information from fuel gauge.
CM_CHARGER_STAT:
get battery presence from chargers.
char **psy_charger_stat;
: An array ending with NULL that has power-supply-class names of
`char **psy_charger_stat;`
An array ending with NULL that has power-supply-class names of
chargers. Each power-supply-class should provide "PRESENT" (if
battery_present is "CM_CHARGER_STAT"), "ONLINE" (shows whether an
external power source is attached or not), and "STATUS" (shows whether
the battery is {"FULL" or not FULL} or {"FULL", "Charging",
"Discharging", "NotCharging"}).
int num_charger_regulators;
struct regulator_bulk_data *charger_regulators;
: Regulators representing the chargers in the form for
`int num_charger_regulators; / struct regulator_bulk_data *charger_regulators;`
Regulators representing the chargers in the form for
regulator framework's bulk functions.
char *psy_fuel_gauge;
: Power-supply-class name of the fuel gauge.
`char *psy_fuel_gauge;`
Power-supply-class name of the fuel gauge.
int (*temperature_out_of_range)(int *mC);
bool measure_battery_temp;
: This callback returns 0 if the temperature is safe for charging,
`int (*temperature_out_of_range)(int *mC); / bool measure_battery_temp;`
This callback returns 0 if the temperature is safe for charging,
a positive number if it is too hot to charge, and a negative number
if it is too cold to charge. With the variable mC, the callback returns
the temperature in 1/1000 of centigrade.
The source of temperature can be battery or ambient one according to
the value of measure_battery_temp.
};
5. Notify Charger-Manager of charger events: cm_notify_event()
=========================================================
==============================================================
If there is an charger event is required to notify
Charger Manager, a charger device driver that triggers the event can call
cm_notify_event(psy, type, msg) to notify the corresponding Charger Manager.

15
Documentation/power/drivers-testing.txt → Documentation/power/drivers-testing.rst
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@ -1,7 +1,11 @@
====================================================
Testing suspend and resume support in device drivers
====================================================
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
1. Preparing the test system
============================
Unfortunately, to effectively test the support for the system-wide suspend and
resume transitions in a driver, it is necessary to suspend and resume a fully
@ -14,19 +18,20 @@ the machine's BIOS.
Of course, for this purpose the test system has to be known to suspend and
resume without the driver being tested. Thus, if possible, you should first
resolve all suspend/resume-related problems in the test system before you start
testing the new driver. Please see Documentation/power/basic-pm-debugging.txt
testing the new driver. Please see Documentation/power/basic-pm-debugging.rst
for more information about the debugging of suspend/resume functionality.
2. Testing the driver
=====================
Once you have resolved the suspend/resume-related problems with your test system
without the new driver, you are ready to test it:
a) Build the driver as a module, load it and try the test modes of hibernation
(see: Documentation/power/basic-pm-debugging.txt, 1).
(see: Documentation/power/basic-pm-debugging.rst, 1).
b) Load the driver and attempt to hibernate in the "reboot", "shutdown" and
"platform" modes (see: Documentation/power/basic-pm-debugging.txt, 1).
"platform" modes (see: Documentation/power/basic-pm-debugging.rst, 1).
c) Compile the driver directly into the kernel and try the test modes of
hibernation.
@ -34,12 +39,12 @@ c) Compile the driver directly into the kernel and try the test modes of
d) Attempt to hibernate with the driver compiled directly into the kernel
in the "reboot", "shutdown" and "platform" modes.
e) Try the test modes of suspend (see: Documentation/power/basic-pm-debugging.txt,
e) Try the test modes of suspend (see: Documentation/power/basic-pm-debugging.rst,
2). [As far as the STR tests are concerned, it should not matter whether or
not the driver is built as a module.]
f) Attempt to suspend to RAM using the s2ram tool with the driver loaded
(see: Documentation/power/basic-pm-debugging.txt, 2).
(see: Documentation/power/basic-pm-debugging.rst, 2).
Each of the above tests should be repeated several times and the STD tests
should be mixed with the STR tests. If any of them fails, the driver cannot be

101
Documentation/power/energy-model.txt → Documentation/power/energy-model.rst
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@ -1,6 +1,6 @@
====================
Energy Model of CPUs
====================
====================
Energy Model of CPUs
====================
1. Overview
-----------
@ -20,7 +20,7 @@ kernel, hence enabling to avoid redundant work.
The figure below depicts an example of drivers (Arm-specific here, but the
approach is applicable to any architecture) providing power costs to the EM
framework, and interested clients reading the data from it.
framework, and interested clients reading the data from it::
+---------------+ +-----------------+ +---------------+
| Thermal (IPA) | | Scheduler (EAS) | | Other |
@ -58,15 +58,17 @@ micro-architectures.
2. Core APIs
------------
2.1 Config options
2.1 Config options
^^^^^^^^^^^^^^^^^^
CONFIG_ENERGY_MODEL must be enabled to use the EM framework.
2.2 Registration of performance domains
2.2 Registration of performance domains
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Drivers are expected to register performance domains into the EM framework by
calling the following API:
calling the following API::
int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
struct em_data_callback *cb);
@ -80,7 +82,8 @@ callback, and kernel/power/energy_model.c for further documentation on this
API.
2.3 Accessing performance domains
2.3 Accessing performance domains
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Subsystems interested in the energy model of a CPU can retrieve it using the
em_cpu_get() API. The energy model tables are allocated once upon creation of
@ -99,46 +102,46 @@ More details about the above APIs can be found in include/linux/energy_model.h.
This section provides a simple example of a CPUFreq driver registering a
performance domain in the Energy Model framework using the (fake) 'foo'
protocol. The driver implements an est_power() function to be provided to the
EM framework.
EM framework::
-> drivers/cpufreq/foo_cpufreq.c
-> drivers/cpufreq/foo_cpufreq.c
01 static int est_power(unsigned long *mW, unsigned long *KHz, int cpu)
02 {
03 long freq, power;
04
05 /* Use the 'foo' protocol to ceil the frequency */
06 freq = foo_get_freq_ceil(cpu, *KHz);
07 if (freq < 0);
08 return freq;
09
10 /* Estimate the power cost for the CPU at the relevant freq. */
11 power = foo_estimate_power(cpu, freq);
12 if (power < 0);
13 return power;
14
15 /* Return the values to the EM framework */
16 *mW = power;
17 *KHz = freq;
18
19 return 0;
20 }
21
22 static int foo_cpufreq_init(struct cpufreq_policy *policy)
23 {
24 struct em_data_callback em_cb = EM_DATA_CB(est_power);
25 int nr_opp, ret;
26
27 /* Do the actual CPUFreq init work ... */
28 ret = do_foo_cpufreq_init(policy);
29 if (ret)
30 return ret;
31
32 /* Find the number of OPPs for this policy */
33 nr_opp = foo_get_nr_opp(policy);
34
35 /* And register the new performance domain */
36 em_register_perf_domain(policy->cpus, nr_opp, &em_cb);
37
38 return 0;
39 }
01 static int est_power(unsigned long *mW, unsigned long *KHz, int cpu)
02 {
03 long freq, power;
04
05 /* Use the 'foo' protocol to ceil the frequency */
06 freq = foo_get_freq_ceil(cpu, *KHz);
07 if (freq < 0);
08 return freq;
09
10 /* Estimate the power cost for the CPU at the relevant freq. */
11 power = foo_estimate_power(cpu, freq);
12 if (power < 0);
13 return power;
14
15 /* Return the values to the EM framework */
16 *mW = power;
17 *KHz = freq;
18
19 return 0;
20 }
21
22 static int foo_cpufreq_init(struct cpufreq_policy *policy)
23 {
24 struct em_data_callback em_cb = EM_DATA_CB(est_power);
25 int nr_opp, ret;
26
27 /* Do the actual CPUFreq init work ... */
28 ret = do_foo_cpufreq_init(policy);
29 if (ret)
30 return ret;
31
32 /* Find the number of OPPs for this policy */
33 nr_opp = foo_get_nr_opp(policy);
34
35 /* And register the new performance domain */
36 em_register_perf_domain(policy->cpus, nr_opp, &em_cb);
37
38 return 0;
39 }

91
Documentation/power/freezing-of-tasks.txt → Documentation/power/freezing-of-tasks.rst
View File

@ -1,13 +1,18 @@
=================
Freezing of tasks
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
=================
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
I. What is the freezing of tasks?
=================================
The freezing of tasks is a mechanism by which user space processes and some
kernel threads are controlled during hibernation or system-wide suspend (on some
architectures).
II. How does it work?
=====================
There are three per-task flags used for that, PF_NOFREEZE, PF_FROZEN
and PF_FREEZER_SKIP (the last one is auxiliary). The tasks that have
@ -41,7 +46,7 @@ explicitly in suitable places or use the wait_event_freezable() or
wait_event_freezable_timeout() macros (defined in include/linux/freezer.h)
that combine interruptible sleep with checking if the task is to be frozen and
calling try_to_freeze(). The main loop of a freezable kernel thread may look
like the following one:
like the following one::
set_freezable();
do {
@ -65,7 +70,7 @@ order to clear the PF_FROZEN flag for each frozen task. Then, the tasks that
have been frozen leave __refrigerator() and continue running.
Rationale behind the functions dealing with freezing and thawing of tasks:
Rationale behind the functions dealing with freezing and thawing of tasks
-------------------------------------------------------------------------
freeze_processes():
@ -86,6 +91,7 @@ thaw_processes():
III. Which kernel threads are freezable?
========================================
Kernel threads are not freezable by default. However, a kernel thread may clear
PF_NOFREEZE for itself by calling set_freezable() (the resetting of PF_NOFREEZE
@ -93,37 +99,39 @@ directly is not allowed). From this point it is regarded as freezable
and must call try_to_freeze() in a suitable place.
IV. Why do we do that?
======================
Generally speaking, there is a couple of reasons to use the freezing of tasks:
1. The principal reason is to prevent filesystems from being damaged after
hibernation. At the moment we have no simple means of checkpointing
filesystems, so if there are any modifications made to filesystem data and/or
metadata on disks, we cannot bring them back to the state from before the
modifications. At the same time each hibernation image contains some
filesystem-related information that must be consistent with the state of the
on-disk data and metadata after the system memory state has been restored from
the image (otherwise the filesystems will be damaged in a nasty way, usually
making them almost impossible to repair). We therefore freeze tasks that might
cause the on-disk filesystems' data and metadata to be modified after the
hibernation image has been created and before the system is finally powered off.
The majority of these are user space processes, but if any of the kernel threads
may cause something like this to happen, they have to be freezable.
hibernation. At the moment we have no simple means of checkpointing
filesystems, so if there are any modifications made to filesystem data and/or
metadata on disks, we cannot bring them back to the state from before the
modifications. At the same time each hibernation image contains some
filesystem-related information that must be consistent with the state of the
on-disk data and metadata after the system memory state has been restored
from the image (otherwise the filesystems will be damaged in a nasty way,
usually making them almost impossible to repair). We therefore freeze
tasks that might cause the on-disk filesystems' data and metadata to be
modified after the hibernation image has been created and before the
system is finally powered off. The majority of these are user space
processes, but if any of the kernel threads may cause something like this
to happen, they have to be freezable.
2. Next, to create the hibernation image we need to free a sufficient amount of
memory (approximately 50% of available RAM) and we need to do that before
devices are deactivated, because we generally need them for swapping out. Then,
after the memory for the image has been freed, we don't want tasks to allocate
additional memory and we prevent them from doing that by freezing them earlier.
[Of course, this also means that device drivers should not allocate substantial
amounts of memory from their .suspend() callbacks before hibernation, but this
is a separate issue.]
memory (approximately 50% of available RAM) and we need to do that before
devices are deactivated, because we generally need them for swapping out.
Then, after the memory for the image has been freed, we don't want tasks
to allocate additional memory and we prevent them from doing that by
freezing them earlier. [Of course, this also means that device drivers
should not allocate substantial amounts of memory from their .suspend()
callbacks before hibernation, but this is a separate issue.]
3. The third reason is to prevent user space processes and some kernel threads
from interfering with the suspending and resuming of devices. A user space
process running on a second CPU while we are suspending devices may, for
example, be troublesome and without the freezing of tasks we would need some
safeguards against race conditions that might occur in such a case.
from interfering with the suspending and resuming of devices. A user space
process running on a second CPU while we are suspending devices may, for
example, be troublesome and without the freezing of tasks we would need some
safeguards against race conditions that might occur in such a case.
Although Linus Torvalds doesn't like the freezing of tasks, he said this in one
of the discussions on LKML (http://lkml.org/lkml/2007/4/27/608):
@ -132,7 +140,7 @@ of the discussions on LKML (http://lkml.org/lkml/2007/4/27/608):
Linus: In many ways, 'at all'.
I _do_ realize the IO request queue issues, and that we cannot actually do
I **do** realize the IO request queue issues, and that we cannot actually do
s2ram with some devices in the middle of a DMA. So we want to be able to
avoid *that*, there's no question about that. And I suspect that stopping
user threads and then waiting for a sync is practically one of the easier
@ -150,17 +158,18 @@ thawed after the driver's .resume() callback has run, so it won't be accessing
the device while it's suspended.
4. Another reason for freezing tasks is to prevent user space processes from
realizing that hibernation (or suspend) operation takes place. Ideally, user
space processes should not notice that such a system-wide operation has occurred
and should continue running without any problems after the restore (or resume
from suspend). Unfortunately, in the most general case this is quite difficult
to achieve without the freezing of tasks. Consider, for example, a process
that depends on all CPUs being online while it's running. Since we need to
disable nonboot CPUs during the hibernation, if this process is not frozen, it
may notice that the number of CPUs has changed and may start to work incorrectly
because of that.
realizing that hibernation (or suspend) operation takes place. Ideally, user
space processes should not notice that such a system-wide operation has
occurred and should continue running without any problems after the restore
(or resume from suspend). Unfortunately, in the most general case this
is quite difficult to achieve without the freezing of tasks. Consider,
for example, a process that depends on all CPUs being online while it's
running. Since we need to disable nonboot CPUs during the hibernation,
if this process is not frozen, it may notice that the number of CPUs has
changed and may start to work incorrectly because of that.
V. Are there any problems related to the freezing of tasks?
===========================================================
Yes, there are.
@ -172,11 +181,12 @@ may be undesirable. That's why kernel threads are not freezable by default.
Second, there are the following two problems related to the freezing of user
space processes:
1. Putting processes into an uninterruptible sleep distorts the load average.
2. Now that we have FUSE, plus the framework for doing device drivers in
userspace, it gets even more complicated because some userspace processes are
now doing the sorts of things that kernel threads do
(https://lists.linux-foundation.org/pipermail/linux-pm/2007-May/012309.html).
userspace, it gets even more complicated because some userspace processes are
now doing the sorts of things that kernel threads do
(https://lists.linux-foundation.org/pipermail/linux-pm/2007-May/012309.html).
The problem 1. seems to be fixable, although it hasn't been fixed so far. The
other one is more serious, but it seems that we can work around it by using
@ -201,6 +211,7 @@ requested early enough using the suspend notifier API described in
Documentation/driver-api/pm/notifiers.rst.
VI. Are there any precautions to be taken to prevent freezing failures?
=======================================================================
Yes, there are.
@ -226,6 +237,8 @@ So, to summarize, use [un]lock_system_sleep() instead of directly using
mutex_[un]lock(&system_transition_mutex). That would prevent freezing failures.
V. Miscellaneous
================
/sys/power/pm_freeze_timeout controls how long it will cost at most to freeze
all user space processes or all freezable kernel threads, in unit of millisecond.
The default value is 20000, with range of unsigned integer.

46
Documentation/power/index.rst Normal file
View File

@ -0,0 +1,46 @@
:orphan:
================
Power Management
================
.. toctree::
:maxdepth: 1
apm-acpi
basic-pm-debugging
charger-manager
drivers-testing
energy-model
freezing-of-tasks
interface
opp
pci
pm_qos_interface
power_supply_class
runtime_pm
s2ram
suspend-and-cpuhotplug
suspend-and-interrupts
swsusp-and-swap-files
swsusp-dmcrypt
swsusp
video
tricks
userland-swsusp
powercap/powercap
regulator/consumer
regulator/design
regulator/machine
regulator/overview
regulator/regulator
.. only:: subproject and html
Indices
=======
* :ref:`genindex`

24
Documentation/power/interface.txt → Documentation/power/interface.rst
View File

@ -1,4 +1,6 @@
===========================================
Power Management Interface for System Sleep
===========================================
Copyright (c) 2016 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
@ -11,10 +13,10 @@ mounted at /sys).
Reading from it returns a list of supported sleep states, encoded as:
'freeze' (Suspend-to-Idle)
'standby' (Power-On Suspend)
'mem' (Suspend-to-RAM)
'disk' (Suspend-to-Disk)
- 'freeze' (Suspend-to-Idle)
- 'standby' (Power-On Suspend)
- 'mem' (Suspend-to-RAM)
- 'disk' (Suspend-to-Disk)
Suspend-to-Idle is always supported. Suspend-to-Disk is always supported
too as long the kernel has been configured to support hibernation at all
@ -32,18 +34,18 @@ Specifically, it tells the kernel what to do after creating a hibernation image.
Reading from it returns a list of supported options encoded as:
'platform' (put the system into sleep using a platform-provided method)
'shutdown' (shut the system down)
'reboot' (reboot the system)
'suspend' (trigger a Suspend-to-RAM transition)
'test_resume' (resume-after-hibernation test mode)
- 'platform' (put the system into sleep using a platform-provided method)
- 'shutdown' (shut the system down)
- 'reboot' (reboot the system)
- 'suspend' (trigger a Suspend-to-RAM transition)
- 'test_resume' (resume-after-hibernation test mode)
The currently selected option is printed in square brackets.
The 'platform' option is only available if the platform provides a special
mechanism to put the system to sleep after creating a hibernation image (ACPI
does that, for example). The 'suspend' option is available if Suspend-to-RAM
is supported. Refer to Documentation/power/basic-pm-debugging.txt for the
is supported. Refer to Documentation/power/basic-pm-debugging.rst for the
description of the 'test_resume' option.
To select an option, write the string representing it to /sys/power/disk.
@ -71,7 +73,7 @@ If /sys/power/pm_trace contains '1', the fingerprint of each suspend/resume
event point in turn will be stored in the RTC memory (overwriting the actual
RTC information), so it will survive a system crash if one occurs right after
storing it and it can be used later to identify the driver that caused the crash
to happen (see Documentation/power/s2ram.txt for more information).
to happen (see Documentation/power/s2ram.rst for more information).
Initially it contains '0' which may be changed to '1' by writing a string
representing a nonzero integer into it.

175
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View File

@ -1,20 +1,23 @@
==========================================
Operating Performance Points (OPP) Library
==========================================
(C) 2009-2010 Nishanth Menon <nm@ti.com>, Texas Instruments Incorporated
Contents
--------
1. Introduction
2. Initial OPP List Registration
3. OPP Search Functions
4. OPP Availability Control Functions
5. OPP Data Retrieval Functions
6. Data Structures
.. Contents
1. Introduction
2. Initial OPP List Registration
3. OPP Search Functions
4. OPP Availability Control Functions
5. OPP Data Retrieval Functions
6. Data Structures
1. Introduction
===============
1.1 What is an Operating Performance Point (OPP)?
-------------------------------------------------
Complex SoCs of today consists of a multiple sub-modules working in conjunction.
In an operational system executing varied use cases, not all modules in the SoC
@ -28,16 +31,19 @@ the device will support per domain are called Operating Performance Points or
OPPs.
As an example:
Let us consider an MPU device which supports the following:
{300MHz at minimum voltage of 1V}, {800MHz at minimum voltage of 1.2V},
{1GHz at minimum voltage of 1.3V}
We can represent these as three OPPs as the following {Hz, uV} tuples:
{300000000, 1000000}
{800000000, 1200000}
{1000000000, 1300000}
- {300000000, 1000000}
- {800000000, 1200000}
- {1000000000, 1300000}
1.2 Operating Performance Points Library
----------------------------------------
OPP library provides a set of helper functions to organize and query the OPP
information. The library is located in drivers/base/power/opp.c and the header
@ -46,9 +52,10 @@ CONFIG_PM_OPP from power management menuconfig menu. OPP library depends on
CONFIG_PM as certain SoCs such as Texas Instrument's OMAP framework allows to
optionally boot at a certain OPP without needing cpufreq.
Typical usage of the OPP library is as follows:
(users) -> registers a set of default OPPs -> (library)
SoC framework -> modifies on required cases certain OPPs -> OPP layer
Typical usage of the OPP library is as follows::
(users) -> registers a set of default OPPs -> (library)
SoC framework -> modifies on required cases certain OPPs -> OPP layer
-> queries to search/retrieve information ->
OPP layer expects each domain to be represented by a unique device pointer. SoC
@ -57,8 +64,9 @@ list is expected to be an optimally small number typically around 5 per device.
This initial list contains a set of OPPs that the framework expects to be safely
enabled by default in the system.
Note on OPP Availability:
------------------------
Note on OPP Availability
^^^^^^^^^^^^^^^^^^^^^^^^
As the system proceeds to operate, SoC framework may choose to make certain
OPPs available or not available on each device based on various external
factors. Example usage: Thermal management or other exceptional situations where
@ -88,7 +96,8 @@ registering the OPPs is maintained by OPP library throughout the device
operation. The SoC framework can subsequently control the availability of the
OPPs dynamically using the dev_pm_opp_enable / disable functions.
dev_pm_opp_add - Add a new OPP for a specific domain represented by the device pointer.
dev_pm_opp_add
Add a new OPP for a specific domain represented by the device pointer.
The OPP is defined using the frequency and voltage. Once added, the OPP
is assumed to be available and control of it's availability can be done
with the dev_pm_opp_enable/disable functions. OPP library internally stores
@ -96,9 +105,11 @@ dev_pm_opp_add - Add a new OPP for a specific domain represented by the device p
used by SoC framework to define a optimal list as per the demands of
SoC usage environment.
WARNING: Do not use this function in interrupt context.
WARNING:
Do not use this function in interrupt context.
Example::
Example:
soc_pm_init()
{
/* Do things */
@ -125,12 +136,15 @@ Callers of these functions shall call dev_pm_opp_put() after they have used the
OPP. Otherwise the memory for the OPP will never get freed and result in
memleak.
dev_pm_opp_find_freq_exact - Search for an OPP based on an *exact* frequency and
dev_pm_opp_find_freq_exact
Search for an OPP based on an *exact* frequency and
availability. This function is especially useful to enable an OPP which
is not available by default.
Example: In a case when SoC framework detects a situation where a
higher frequency could be made available, it can use this function to
find the OPP prior to call the dev_pm_opp_enable to actually make it available.
find the OPP prior to call the dev_pm_opp_enable to actually make
it available::
opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false);
dev_pm_opp_put(opp);
/* dont operate on the pointer.. just do a sanity check.. */
@ -141,27 +155,34 @@ dev_pm_opp_find_freq_exact - Search for an OPP based on an *exact* frequency and
dev_pm_opp_enable(dev,1000000000);
}
NOTE: This is the only search function that operates on OPPs which are
not available.
NOTE:
This is the only search function that operates on OPPs which are
not available.
dev_pm_opp_find_freq_floor - Search for an available OPP which is *at most* the
dev_pm_opp_find_freq_floor
Search for an available OPP which is *at most* the
provided frequency. This function is useful while searching for a lesser
match OR operating on OPP information in the order of decreasing
frequency.
Example: To find the highest opp for a device:
Example: To find the highest opp for a device::
freq = ULONG_MAX;
opp = dev_pm_opp_find_freq_floor(dev, &freq);
dev_pm_opp_put(opp);
dev_pm_opp_find_freq_ceil - Search for an available OPP which is *at least* the
dev_pm_opp_find_freq_ceil
Search for an available OPP which is *at least* the
provided frequency. This function is useful while searching for a
higher match OR operating on OPP information in the order of increasing
frequency.
Example 1: To find the lowest opp for a device:
Example 1: To find the lowest opp for a device::
freq = 0;
opp = dev_pm_opp_find_freq_ceil(dev, &freq);
dev_pm_opp_put(opp);
Example 2: A simplified implementation of a SoC cpufreq_driver->target:
Example 2: A simplified implementation of a SoC cpufreq_driver->target::
soc_cpufreq_target(..)
{
/* Do stuff like policy checks etc. */
@ -184,12 +205,15 @@ fine grained dynamic control of which sets of OPPs are operationally available.
These functions are intended to *temporarily* remove an OPP in conditions such
as thermal considerations (e.g. don't use OPPx until the temperature drops).
WARNING: Do not use these functions in interrupt context.
WARNING:
Do not use these functions in interrupt context.
dev_pm_opp_enable - Make a OPP available for operation.
dev_pm_opp_enable
Make a OPP available for operation.
Example: Lets say that 1GHz OPP is to be made available only if the
SoC temperature is lower than a certain threshold. The SoC framework
implementation might choose to do something as follows:
implementation might choose to do something as follows::
if (cur_temp < temp_low_thresh) {
/* Enable 1GHz if it was disabled */
opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false);
@ -201,10 +225,12 @@ dev_pm_opp_enable - Make a OPP available for operation.
goto try_something_else;
}
dev_pm_opp_disable - Make an OPP to be not available for operation
dev_pm_opp_disable
Make an OPP to be not available for operation
Example: Lets say that 1GHz OPP is to be disabled if the temperature
exceeds a threshold value. The SoC framework implementation might
choose to do something as follows:
choose to do something as follows::
if (cur_temp > temp_high_thresh) {
/* Disable 1GHz if it was enabled */
opp = dev_pm_opp_find_freq_exact(dev, 1000000000, true);
@ -223,11 +249,13 @@ information from the OPP structure is necessary. Once an OPP pointer is
retrieved using the search functions, the following functions can be used by SoC
framework to retrieve the information represented inside the OPP layer.
dev_pm_opp_get_voltage - Retrieve the voltage represented by the opp pointer.
dev_pm_opp_get_voltage
Retrieve the voltage represented by the opp pointer.
Example: At a cpufreq transition to a different frequency, SoC
framework requires to set the voltage represented by the OPP using
the regulator framework to the Power Management chip providing the
voltage.
voltage::
soc_switch_to_freq_voltage(freq)
{
/* do things */
@ -239,10 +267,12 @@ dev_pm_opp_get_voltage - Retrieve the voltage represented by the opp pointer.
/* do other things */
}
dev_pm_opp_get_freq - Retrieve the freq represented by the opp pointer.
dev_pm_opp_get_freq
Retrieve the freq represented by the opp pointer.
Example: Lets say the SoC framework uses a couple of helper functions
we could pass opp pointers instead of doing additional parameters to
handle quiet a bit of data parameters.
handle quiet a bit of data parameters::
soc_cpufreq_target(..)
{
/* do things.. */
@ -264,9 +294,11 @@ dev_pm_opp_get_freq - Retrieve the freq represented by the opp pointer.
/* do things.. */
}
dev_pm_opp_get_opp_count - Retrieve the number of available opps for a device
dev_pm_opp_get_opp_count
Retrieve the number of available opps for a device
Example: Lets say a co-processor in the SoC needs to know the available
frequencies in a table, the main processor can notify as following:
frequencies in a table, the main processor can notify as following::
soc_notify_coproc_available_frequencies()
{
/* Do things */
@ -289,54 +321,59 @@ dev_pm_opp_get_opp_count - Retrieve the number of available opps for a device
==================
Typically an SoC contains multiple voltage domains which are variable. Each
domain is represented by a device pointer. The relationship to OPP can be
represented as follows:
SoC
|- device 1
| |- opp 1 (availability, freq, voltage)
| |- opp 2 ..
... ...
| `- opp n ..
|- device 2
...
`- device m
represented as follows::
SoC
|- device 1
| |- opp 1 (availability, freq, voltage)
| |- opp 2 ..
... ...
| `- opp n ..
|- device 2
...
`- device m
OPP library maintains a internal list that the SoC framework populates and
accessed by various functions as described above. However, the structures
representing the actual OPPs and domains are internal to the OPP library itself
to allow for suitable abstraction reusable across systems.
struct dev_pm_opp - The internal data structure of OPP library which is used to
struct dev_pm_opp
The internal data structure of OPP library which is used to
represent an OPP. In addition to the freq, voltage, availability
information, it also contains internal book keeping information required
for the OPP library to operate on. Pointer to this structure is
provided back to the users such as SoC framework to be used as a
identifier for OPP in the interactions with OPP layer.
WARNING: The struct dev_pm_opp pointer should not be parsed or modified by the
users. The defaults of for an instance is populated by dev_pm_opp_add, but the
availability of the OPP can be modified by dev_pm_opp_enable/disable functions.
WARNING:
The struct dev_pm_opp pointer should not be parsed or modified by the
users. The defaults of for an instance is populated by
dev_pm_opp_add, but the availability of the OPP can be modified
by dev_pm_opp_enable/disable functions.
struct device - This is used to identify a domain to the OPP layer. The
struct device
This is used to identify a domain to the OPP layer. The
nature of the device and it's implementation is left to the user of
OPP library such as the SoC framework.
Overall, in a simplistic view, the data structure operations is represented as
following:
following::
Initialization / modification:
+-----+ /- dev_pm_opp_enable
dev_pm_opp_add --> | opp | <-------
| +-----+ \- dev_pm_opp_disable
\-------> domain_info(device)
Initialization / modification:
+-----+ /- dev_pm_opp_enable
dev_pm_opp_add --> | opp | <-------
| +-----+ \- dev_pm_opp_disable
\-------> domain_info(device)
Search functions:
/-- dev_pm_opp_find_freq_ceil ---\ +-----+
domain_info<---- dev_pm_opp_find_freq_exact -----> | opp |
\-- dev_pm_opp_find_freq_floor ---/ +-----+
Search functions:
/-- dev_pm_opp_find_freq_ceil ---\ +-----+
domain_info<---- dev_pm_opp_find_freq_exact -----> | opp |
\-- dev_pm_opp_find_freq_floor ---/ +-----+
Retrieval functions:
+-----+ /- dev_pm_opp_get_voltage
| opp | <---
+-----+ \- dev_pm_opp_get_freq
Retrieval functions:
+-----+ /- dev_pm_opp_get_voltage
| opp | <---
+-----+ \- dev_pm_opp_get_freq
domain_info <- dev_pm_opp_get_opp_count
domain_info <- dev_pm_opp_get_opp_count

87
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View File

@ -1,4 +1,6 @@
====================
PCI Power Management
====================
Copyright (c) 2010 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
@ -9,14 +11,14 @@ management. Based on previous work by Patrick Mochel <mochel@transmeta.com>
This document only covers the aspects of power management specific to PCI
devices. For general description of the kernel's interfaces related to device
power management refer to Documentation/driver-api/pm/devices.rst and
Documentation/power/runtime_pm.txt.
Documentation/power/runtime_pm.rst.
---------------------------------------------------------------------------
.. contents:
1. Hardware and Platform Support for PCI Power Management
2. PCI Subsystem and Device Power Management
3. PCI Device Drivers and Power Management
4. Resources
1. Hardware and Platform Support for PCI Power Management
2. PCI Subsystem and Device Power Management
3. PCI Device Drivers and Power Management
4. Resources
1. Hardware and Platform Support for PCI Power Management
@ -24,6 +26,7 @@ Documentation/power/runtime_pm.txt.
1.1. Native and Platform-Based Power Management
-----------------------------------------------
In general, power management is a feature allowing one to save energy by putting
devices into states in which they draw less power (low-power states) at the
price of reduced functionality or performance.
@ -67,6 +70,7 @@ mechanisms have to be used simultaneously to obtain the desired result.
1.2. Native PCI Power Management
--------------------------------
The PCI Bus Power Management Interface Specification (PCI PM Spec) was
introduced between the PCI 2.1 and PCI 2.2 Specifications. It defined a
standard interface for performing various operations related to power
@ -134,6 +138,7 @@ sufficiently active to generate a wakeup signal.
1.3. ACPI Device Power Management
---------------------------------
The platform firmware support for the power management of PCI devices is
system-specific. However, if the system in question is compliant with the
Advanced Configuration and Power Interface (ACPI) Specification, like the
@ -194,6 +199,7 @@ enabled for the device to be able to generate wakeup signals.
1.4. Wakeup Signaling
---------------------
Wakeup signals generated by PCI devices, either as native PCI PMEs, or as
a result of the execution of the _DSW (or _PSW) ACPI control method before
putting the device into a low-power state, have to be caught and handled as
@ -265,14 +271,15 @@ the native PCI Express PME signaling cannot be used by the kernel in that case.
2.1. Device Power Management Callbacks
--------------------------------------
The PCI Subsystem participates in the power management of PCI devices in a
number of ways. First of all, it provides an intermediate code layer between
the device power management core (PM core) and PCI device drivers.
Specifically, the pm field of the PCI subsystem's struct bus_type object,
pci_bus_type, points to a struct dev_pm_ops object, pci_dev_pm_ops, containing
pointers to several device power management callbacks:
pointers to several device power management callbacks::
const struct dev_pm_ops pci_dev_pm_ops = {
const struct dev_pm_ops pci_dev_pm_ops = {
.prepare = pci_pm_prepare,
.complete = pci_pm_complete,
.suspend = pci_pm_suspend,
@ -290,7 +297,7 @@ const struct dev_pm_ops pci_dev_pm_ops = {
.runtime_suspend = pci_pm_runtime_suspend,
.runtime_resume = pci_pm_runtime_resume,
.runtime_idle = pci_pm_runtime_idle,
};
};
These callbacks are executed by the PM core in various situations related to
device power management and they, in turn, execute power management callbacks
@ -299,9 +306,9 @@ involving some standard configuration registers of PCI devices that device
drivers need not know or care about.
The structure representing a PCI device, struct pci_dev, contains several fields
that these callbacks operate on:
that these callbacks operate on::
struct pci_dev {
struct pci_dev {
...
pci_power_t current_state; /* Current operating state. */
int pm_cap; /* PM capability offset in the
@ -315,13 +322,14 @@ struct pci_dev {
unsigned int wakeup_prepared:1; /* Device prepared for wake up */
unsigned int d3_delay; /* D3->D0 transition time in ms */
...
};
};
They also indirectly use some fields of the struct device that is embedded in
struct pci_dev.
2.2. Device Initialization
--------------------------
The PCI subsystem's first task related to device power management is to
prepare the device for power management and initialize the fields of struct
pci_dev used for this purpose. This happens in two functions defined in
@ -348,10 +356,11 @@ during system-wide transitions to a sleep state and back to the working state.
2.3. Runtime Device Power Management
------------------------------------
The PCI subsystem plays a vital role in the runtime power management of PCI
devices. For this purpose it uses the general runtime power management
(runtime PM) framework described in Documentation/power/runtime_pm.txt.
Namely, it provides subsystem-level callbacks:
(runtime PM) framework described in Documentation/power/runtime_pm.rst.
Namely, it provides subsystem-level callbacks::
pci_pm_runtime_suspend()
pci_pm_runtime_resume()
@ -425,13 +434,14 @@ to the given subsystem before the next phase begins. These phases always run
after tasks have been frozen.
2.4.1. System Suspend
^^^^^^^^^^^^^^^^^^^^^
When the system is going into a sleep state in which the contents of memory will
be preserved, such as one of the ACPI sleep states S1-S3, the phases are:
prepare, suspend, suspend_noirq.
The following PCI bus type's callbacks, respectively, are used in these phases:
The following PCI bus type's callbacks, respectively, are used in these phases::
pci_pm_prepare()
pci_pm_suspend()
@ -492,6 +502,7 @@ this purpose). PCI device drivers are not encouraged to do that, but in some
rare cases doing that in the driver may be the optimum approach.
2.4.2. System Resume
^^^^^^^^^^^^^^^^^^^^
When the system is undergoing a transition from a sleep state in which the
contents of memory have been preserved, such as one of the ACPI sleep states
@ -500,7 +511,7 @@ S1-S3, into the working state (ACPI S0), the phases are:
resume_noirq, resume, complete.
The following PCI bus type's callbacks, respectively, are executed in these
phases:
phases::
pci_pm_resume_noirq()
pci_pm_resume()
@ -539,6 +550,7 @@ The pci_pm_complete() routine only executes the device driver's pm->complete()
callback, if defined.
2.4.3. System Hibernation
^^^^^^^^^^^^^^^^^^^^^^^^^
System hibernation is more complicated than system suspend, because it requires
a system image to be created and written into a persistent storage medium. The
@ -551,7 +563,7 @@ to be free) in the following three phases:
prepare, freeze, freeze_noirq
that correspond to the PCI bus type's callbacks:
that correspond to the PCI bus type's callbacks::
pci_pm_prepare()
pci_pm_freeze()
@ -580,7 +592,7 @@ back to the fully functional state and this is done in the following phases:
thaw_noirq, thaw, complete
using the following PCI bus type's callbacks:
using the following PCI bus type's callbacks::
pci_pm_thaw_noirq()
pci_pm_thaw()
@ -608,7 +620,7 @@ three phases:
where the prepare phase is exactly the same as for system suspend. The other
two phases are analogous to the suspend and suspend_noirq phases, respectively.
The PCI subsystem-level callbacks they correspond to
The PCI subsystem-level callbacks they correspond to::
pci_pm_poweroff()
pci_pm_poweroff_noirq()
@ -618,6 +630,7 @@ although they don't attempt to save the device's standard configuration
registers.
2.4.4. System Restore
^^^^^^^^^^^^^^^^^^^^^
System restore requires a hibernation image to be loaded into memory and the
pre-hibernation memory contents to be restored before the pre-hibernation system
@ -653,7 +666,7 @@ phases:
The first two of these are analogous to the resume_noirq and resume phases
described above, respectively, and correspond to the following PCI subsystem
callbacks:
callbacks::
pci_pm_restore_noirq()
pci_pm_restore()
@ -671,6 +684,7 @@ resume.
3.1. Power Management Callbacks
-------------------------------
PCI device drivers participate in power management by providing callbacks to be
executed by the PCI subsystem's power management routines described above and by
controlling the runtime power management of their devices.
@ -698,6 +712,7 @@ defined, though, they are expected to behave as described in the following
subsections.
3.1.1. prepare()
^^^^^^^^^^^^^^^^
The prepare() callback is executed during system suspend, during hibernation
(when a hibernation image is about to be created), during power-off after
@ -716,6 +731,7 @@ preallocated earlier, for example in a suspend/hibernate notifier as described
in Documentation/driver-api/pm/notifiers.rst).
3.1.2. suspend()
^^^^^^^^^^^^^^^^
The suspend() callback is only executed during system suspend, after prepare()
callbacks have been executed for all devices in the system.
@ -742,6 +758,7 @@ operations relying on the driver's ability to handle interrupts should be
carried out in this callback.
3.1.3. suspend_noirq()
^^^^^^^^^^^^^^^^^^^^^^
The suspend_noirq() callback is only executed during system suspend, after
suspend() callbacks have been executed for all devices in the system and
@ -753,6 +770,7 @@ suspend_noirq() can carry out operations that would cause race conditions to
arise if they were performed in suspend().
3.1.4. freeze()
^^^^^^^^^^^^^^^
The freeze() callback is hibernation-specific and is executed in two situations,
during hibernation, after prepare() callbacks have been executed for all devices
@ -770,6 +788,7 @@ or put it into a low-power state. Still, either it or freeze_noirq() should
save the device's standard configuration registers using pci_save_state().
3.1.5. freeze_noirq()
^^^^^^^^^^^^^^^^^^^^^
The freeze_noirq() callback is hibernation-specific. It is executed during
hibernation, after prepare() and freeze() callbacks have been executed for all
@ -786,6 +805,7 @@ The difference between freeze_noirq() and freeze() is analogous to the
difference between suspend_noirq() and suspend().
3.1.6. poweroff()
^^^^^^^^^^^^^^^^^
The poweroff() callback is hibernation-specific. It is executed when the system
is about to be powered off after saving a hibernation image to a persistent
@ -802,6 +822,7 @@ into a low-power state, respectively, but it need not save the device's standard
configuration registers.
3.1.7. poweroff_noirq()
^^^^^^^^^^^^^^^^^^^^^^^
The poweroff_noirq() callback is hibernation-specific. It is executed after
poweroff() callbacks have been executed for all devices in the system.
@ -814,6 +835,7 @@ The difference between poweroff_noirq() and poweroff() is analogous to the
difference between suspend_noirq() and suspend().
3.1.8. resume_noirq()
^^^^^^^^^^^^^^^^^^^^^
The resume_noirq() callback is only executed during system resume, after the
PM core has enabled the non-boot CPUs. The driver's interrupt handler will not
@ -827,6 +849,7 @@ it should only be used for performing operations that would lead to race
conditions if carried out by resume().
3.1.9. resume()
^^^^^^^^^^^^^^^
The resume() callback is only executed during system resume, after
resume_noirq() callbacks have been executed for all devices in the system and
@ -837,6 +860,7 @@ device and bringing it back to the fully functional state. The device should be
able to process I/O in a usual way after resume() has returned.
3.1.10. thaw_noirq()
^^^^^^^^^^^^^^^^^^^^
The thaw_noirq() callback is hibernation-specific. It is executed after a
system image has been created and the non-boot CPUs have been enabled by the PM
@ -851,6 +875,7 @@ freeze() and freeze_noirq(), so in general it does not need to modify the
contents of the device's registers.
3.1.11. thaw()
^^^^^^^^^^^^^^
The thaw() callback is hibernation-specific. It is executed after thaw_noirq()
callbacks have been executed for all devices in the system and after device
@ -860,6 +885,7 @@ This callback is responsible for restoring the pre-freeze configuration of
the device, so that it will work in a usual way after thaw() has returned.
3.1.12. restore_noirq()
^^^^^^^^^^^^^^^^^^^^^^^
The restore_noirq() callback is hibernation-specific. It is executed in the
restore_noirq phase of hibernation, when the boot kernel has passed control to
@ -875,6 +901,7 @@ For the vast majority of PCI device drivers there is no difference between
resume_noirq() and restore_noirq().
3.1.13. restore()
^^^^^^^^^^^^^^^^^
The restore() callback is hibernation-specific. It is executed after
restore_noirq() callbacks have been executed for all devices in the system and
@ -888,14 +915,17 @@ For the vast majority of PCI device drivers there is no difference between
resume() and restore().
3.1.14. complete()
^^^^^^^^^^^^^^^^^^
The complete() callback is executed in the following situations:
- during system resume, after resume() callbacks have been executed for all
devices,
- during hibernation, before saving the system image, after thaw() callbacks
have been executed for all devices,
- during system restore, when the system is going back to its pre-hibernation
state, after restore() callbacks have been executed for all devices.
It also may be executed if the loading of a hibernation image into memory fails
(in that case it is run after thaw() callbacks have been executed for all
devices that have drivers in the boot kernel).
@ -904,6 +934,7 @@ This callback is entirely optional, although it may be necessary if the
prepare() callback performs operations that need to be reversed.
3.1.15. runtime_suspend()
^^^^^^^^^^^^^^^^^^^^^^^^^
The runtime_suspend() callback is specific to device runtime power management
(runtime PM). It is executed by the PM core's runtime PM framework when the
@ -915,6 +946,7 @@ put into a low-power state, but it must allow the PCI subsystem to perform all
of the PCI-specific actions necessary for suspending the device.
3.1.16. runtime_resume()
^^^^^^^^^^^^^^^^^^^^^^^^
The runtime_resume() callback is specific to device runtime PM. It is executed
by the PM core's runtime PM framework when the device is about to be resumed
@ -927,6 +959,7 @@ The device is expected to be able to process I/O in the usual way after
runtime_resume() has returned.
3.1.17. runtime_idle()
^^^^^^^^^^^^^^^^^^^^^^
The runtime_idle() callback is specific to device runtime PM. It is executed
by the PM core's runtime PM framework whenever it may be desirable to suspend
@ -939,6 +972,7 @@ PCI subsystem will call pm_runtime_suspend() for the device, which in turn will
cause the driver's runtime_suspend() callback to be executed.
3.1.18. Pointing Multiple Callback Pointers to One Routine
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Although in principle each of the callbacks described in the previous
subsections can be defined as a separate function, it often is convenient to
@ -962,6 +996,7 @@ dev_pm_ops to indicate that one suspend routine is to be pointed to by the
be pointed to by the .resume(), .thaw(), and .restore() members.
3.1.19. Driver Flags for Power Management
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The PM core allows device drivers to set flags that influence the handling of
power management for the devices by the core itself and by middle layer code
@ -1007,6 +1042,7 @@ it.
3.2. Device Runtime Power Management
------------------------------------
In addition to providing device power management callbacks PCI device drivers
are responsible for controlling the runtime power management (runtime PM) of
their devices.
@ -1073,22 +1109,27 @@ device the PM core automatically queues a request to check if the device is
idle), device drivers are generally responsible for queuing power management
requests for their devices. For this purpose they should use the runtime PM
helper functions provided by the PM core, discussed in
Documentation/power/runtime_pm.txt.
Documentation/power/runtime_pm.rst.
Devices can also be suspended and resumed synchronously, without placing a
request into pm_wq. In the majority of cases this also is done by their
drivers that use helper functions provided by the PM core for this purpose.
For more information on the runtime PM of devices refer to
Documentation/power/runtime_pm.txt.
Documentation/power/runtime_pm.rst.
4. Resources
============
PCI Local Bus Specification, Rev. 3.0
PCI Bus Power Management Interface Specification, Rev. 1.2
Advanced Configuration and Power Interface (ACPI) Specification, Rev. 3.0b
PCI Express Base Specification, Rev. 2.0
Documentation/driver-api/pm/devices.rst
Documentation/power/runtime_pm.txt
Documentation/power/runtime_pm.rst

127
Documentation/power/pm_qos_interface.txt → Documentation/power/pm_qos_interface.rst
View File

@ -1,4 +1,6 @@
PM Quality Of Service Interface.
===============================
PM Quality Of Service Interface
===============================
This interface provides a kernel and user mode interface for registering
performance expectations by drivers, subsystems and user space applications on
@ -11,6 +13,7 @@ memory_bandwidth.
constraints and PM QoS flags.
Each parameters have defined units:
* latency: usec
* timeout: usec
* throughput: kbs (kilo bit / sec)
@ -18,6 +21,7 @@ Each parameters have defined units:
1. PM QoS framework
===================
The infrastructure exposes multiple misc device nodes one per implemented
parameter. The set of parameters implement is defined by pm_qos_power_init()
@ -37,38 +41,39 @@ reading the aggregated value does not require any locking mechanism.
From kernel mode the use of this interface is simple:
void pm_qos_add_request(handle, param_class, target_value):
Will insert an element into the list for that identified PM QoS class with the
target value. Upon change to this list the new target is recomputed and any
registered notifiers are called only if the target value is now different.
Clients of pm_qos need to save the returned handle for future use in other
pm_qos API functions.
Will insert an element into the list for that identified PM QoS class with the
target value. Upon change to this list the new target is recomputed and any
registered notifiers are called only if the target value is now different.
Clients of pm_qos need to save the returned handle for future use in other
pm_qos API functions.
void pm_qos_update_request(handle, new_target_value):
Will update the list element pointed to by the handle with the new target value
and recompute the new aggregated target, calling the notification tree if the
target is changed.
Will update the list element pointed to by the handle with the new target value
and recompute the new aggregated target, calling the notification tree if the
target is changed.
void pm_qos_remove_request(handle):
Will remove the element. After removal it will update the aggregate target and
call the notification tree if the target was changed as a result of removing
the request.
Will remove the element. After removal it will update the aggregate target and
call the notification tree if the target was changed as a result of removing
the request.
int pm_qos_request(param_class):
Returns the aggregated value for a given PM QoS class.
Returns the aggregated value for a given PM QoS class.
int pm_qos_request_active(handle):
Returns if the request is still active, i.e. it has not been removed from a
PM QoS class constraints list.
Returns if the request is still active, i.e. it has not been removed from a
PM QoS class constraints list.
int pm_qos_add_notifier(param_class, notifier):
Adds a notification callback function to the PM QoS class. The callback is
called when the aggregated value for the PM QoS class is changed.
Adds a notification callback function to the PM QoS class. The callback is
called when the aggregated value for the PM QoS class is changed.
int pm_qos_remove_notifier(int param_class, notifier):
Removes the notification callback function for the PM QoS class.
Removes the notification callback function for the PM QoS class.
From user mode:
Only processes can register a pm_qos request. To provide for automatic
cleanup of a process, the interface requires the process to register its
parameter requests in the following way:
@ -89,6 +94,7 @@ node.
2. PM QoS per-device latency and flags framework
================================================
For each device, there are three lists of PM QoS requests. Two of them are
maintained along with the aggregated targets of resume latency and active
@ -107,73 +113,80 @@ the aggregated value does not require any locking mechanism.
From kernel mode the use of this interface is the following:
int dev_pm_qos_add_request(device, handle, type, value):
Will insert an element into the list for that identified device with the
target value. Upon change to this list the new target is recomputed and any
registered notifiers are called only if the target value is now different.
Clients of dev_pm_qos need to save the handle for future use in other
dev_pm_qos API functions.
Will insert an element into the list for that identified device with the
target value. Upon change to this list the new target is recomputed and any
registered notifiers are called only if the target value is now different.
Clients of dev_pm_qos need to save the handle for future use in other
dev_pm_qos API functions.
int dev_pm_qos_update_request(handle, new_value):
Will update the list element pointed to by the handle with the new target value
and recompute the new aggregated target, calling the notification trees if the
target is changed.
Will update the list element pointed to by the handle with the new target
value and recompute the new aggregated target, calling the notification
trees if the target is changed.
int dev_pm_qos_remove_request(handle):
Will remove the element. After removal it will update the aggregate target and
call the notification trees if the target was changed as a result of removing
the request.
Will remove the element. After removal it will update the aggregate target
and call the notification trees if the target was changed as a result of
removing the request.
s32 dev_pm_qos_read_value(device):
Returns the aggregated value for a given device's constraints list.
Returns the aggregated value for a given device's constraints list.
enum pm_qos_flags_status dev_pm_qos_flags(device, mask)
Check PM QoS flags of the given device against the given mask of flags.
The meaning of the return values is as follows:
PM_QOS_FLAGS_ALL: All flags from the mask are set
PM_QOS_FLAGS_SOME: Some flags from the mask are set
PM_QOS_FLAGS_NONE: No flags from the mask are set
PM_QOS_FLAGS_UNDEFINED: The device's PM QoS structure has not been
initialized or the list of requests is empty.
Check PM QoS flags of the given device against the given mask of flags.
The meaning of the return values is as follows:
PM_QOS_FLAGS_ALL:
All flags from the mask are set
PM_QOS_FLAGS_SOME:
Some flags from the mask are set
PM_QOS_FLAGS_NONE:
No flags from the mask are set
PM_QOS_FLAGS_UNDEFINED:
The device's PM QoS structure has not been initialized
or the list of requests is empty.
int dev_pm_qos_add_ancestor_request(dev, handle, type, value)
Add a PM QoS request for the first direct ancestor of the given device whose
power.ignore_children flag is unset (for DEV_PM_QOS_RESUME_LATENCY requests)
or whose power.set_latency_tolerance callback pointer is not NULL (for
DEV_PM_QOS_LATENCY_TOLERANCE requests).
Add a PM QoS request for the first direct ancestor of the given device whose
power.ignore_children flag is unset (for DEV_PM_QOS_RESUME_LATENCY requests)
or whose power.set_latency_tolerance callback pointer is not NULL (for
DEV_PM_QOS_LATENCY_TOLERANCE requests).
int dev_pm_qos_expose_latency_limit(device, value)
Add a request to the device's PM QoS list of resume latency constraints and
create a sysfs attribute pm_qos_resume_latency_us under the device's power
directory allowing user space to manipulate that request.
Add a request to the device's PM QoS list of resume latency constraints and
create a sysfs attribute pm_qos_resume_latency_us under the device's power
directory allowing user space to manipulate that request.
void dev_pm_qos_hide_latency_limit(device)
Drop the request added by dev_pm_qos_expose_latency_limit() from the device's
PM QoS list of resume latency constraints and remove sysfs attribute
pm_qos_resume_latency_us from the device's power directory.
Drop the request added by dev_pm_qos_expose_latency_limit() from the device's
PM QoS list of resume latency constraints and remove sysfs attribute
pm_qos_resume_latency_us from the device's power directory.
int dev_pm_qos_expose_flags(device, value)
Add a request to the device's PM QoS list of flags and create sysfs attribute
pm_qos_no_power_off under the device's power directory allowing user space to
change the value of the PM_QOS_FLAG_NO_POWER_OFF flag.
Add a request to the device's PM QoS list of flags and create sysfs attribute
pm_qos_no_power_off under the device's power directory allowing user space to
change the value of the PM_QOS_FLAG_NO_POWER_OFF flag.
void dev_pm_qos_hide_flags(device)
Drop the request added by dev_pm_qos_expose_flags() from the device's PM QoS list
of flags and remove sysfs attribute pm_qos_no_power_off from the device's power
directory.
Drop the request added by dev_pm_qos_expose_flags() from the device's PM QoS list
of flags and remove sysfs attribute pm_qos_no_power_off from the device's power
directory.
Notification mechanisms:
The per-device PM QoS framework has a per-device notification tree.
int dev_pm_qos_add_notifier(device, notifier):
Adds a notification callback function for the device.
The callback is called when the aggregated value of the device constraints list
is changed (for resume latency device PM QoS only).
Adds a notification callback function for the device.
The callback is called when the aggregated value of the device constraints list
is changed (for resume latency device PM QoS only).
int dev_pm_qos_remove_notifier(device, notifier):
Removes the notification callback function for the device.
Removes the notification callback function for the device.
Active state latency tolerance
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This device PM QoS type is used to support systems in which hardware may switch
to energy-saving operation modes on the fly. In those systems, if the operation

282
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View File

@ -0,0 +1,282 @@
========================
Linux power supply class
========================
Synopsis
~~~~~~~~
Power supply class used to represent battery, UPS, AC or DC power supply
properties to user-space.
It defines core set of attributes, which should be applicable to (almost)
every power supply out there. Attributes are available via sysfs and uevent
interfaces.
Each attribute has well defined meaning, up to unit of measure used. While
the attributes provided are believed to be universally applicable to any
power supply, specific monitoring hardware may not be able to provide them
all, so any of them may be skipped.
Power supply class is extensible, and allows to define drivers own attributes.
The core attribute set is subject to the standard Linux evolution (i.e.
if it will be found that some attribute is applicable to many power supply
types or their drivers, it can be added to the core set).
It also integrates with LED framework, for the purpose of providing
typically expected feedback of battery charging/fully charged status and
AC/USB power supply online status. (Note that specific details of the
indication (including whether to use it at all) are fully controllable by
user and/or specific machine defaults, per design principles of LED
framework).
Attributes/properties
~~~~~~~~~~~~~~~~~~~~~
Power supply class has predefined set of attributes, this eliminates code
duplication across drivers. Power supply class insist on reusing its
predefined attributes *and* their units.
So, userspace gets predictable set of attributes and their units for any
kind of power supply, and can process/present them to a user in consistent
manner. Results for different power supplies and machines are also directly
comparable.
See drivers/power/supply/ds2760_battery.c and drivers/power/supply/pda_power.c
for the example how to declare and handle attributes.
Units
~~~~~
Quoting include/linux/power_supply.h:
All voltages, currents, charges, energies, time and temperatures in µV,
µA, µAh, µWh, seconds and tenths of degree Celsius unless otherwise
stated. It's driver's job to convert its raw values to units in which
this class operates.
Attributes/properties detailed
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+--------------------------------------------------------------------------+
| **Charge/Energy/Capacity - how to not confuse** |
+--------------------------------------------------------------------------+
| **Because both "charge" (µAh) and "energy" (µWh) represents "capacity" |
| of battery, this class distinguish these terms. Don't mix them!** |
| |
| - `CHARGE_*` |
| attributes represents capacity in µAh only. |
| - `ENERGY_*` |
| attributes represents capacity in µWh only. |
| - `CAPACITY` |
| attribute represents capacity in *percents*, from 0 to 100. |
+--------------------------------------------------------------------------+
Postfixes:
_AVG
*hardware* averaged value, use it if your hardware is really able to
report averaged values.
_NOW
momentary/instantaneous values.
STATUS
this attribute represents operating status (charging, full,
discharging (i.e. powering a load), etc.). This corresponds to
`BATTERY_STATUS_*` values, as defined in battery.h.
CHARGE_TYPE
batteries can typically charge at different rates.
This defines trickle and fast charges. For batteries that
are already charged or discharging, 'n/a' can be displayed (or
'unknown', if the status is not known).
AUTHENTIC
indicates the power supply (battery or charger) connected
to the platform is authentic(1) or non authentic(0).
HEALTH
represents health of the battery, values corresponds to
POWER_SUPPLY_HEALTH_*, defined in battery.h.
VOLTAGE_OCV
open circuit voltage of the battery.
VOLTAGE_MAX_DESIGN, VOLTAGE_MIN_DESIGN
design values for maximal and minimal power supply voltages.
Maximal/minimal means values of voltages when battery considered
"full"/"empty" at normal conditions. Yes, there is no direct relation
between voltage and battery capacity, but some dumb
batteries use voltage for very approximated calculation of capacity.
Battery driver also can use this attribute just to inform userspace
about maximal and minimal voltage thresholds of a given battery.
VOLTAGE_MAX, VOLTAGE_MIN
same as _DESIGN voltage values except that these ones should be used
if hardware could only guess (measure and retain) the thresholds of a
given power supply.
VOLTAGE_BOOT
Reports the voltage measured during boot
CURRENT_BOOT
Reports the current measured during boot
CHARGE_FULL_DESIGN, CHARGE_EMPTY_DESIGN
design charge values, when battery considered full/empty.
ENERGY_FULL_DESIGN, ENERGY_EMPTY_DESIGN
same as above but for energy.
CHARGE_FULL, CHARGE_EMPTY
These attributes means "last remembered value of charge when battery
became full/empty". It also could mean "value of charge when battery
considered full/empty at given conditions (temperature, age)".
I.e. these attributes represents real thresholds, not design values.
ENERGY_FULL, ENERGY_EMPTY
same as above but for energy.
CHARGE_COUNTER
the current charge counter (in µAh). This could easily
be negative; there is no empty or full value. It is only useful for
relative, time-based measurements.
PRECHARGE_CURRENT
the maximum charge current during precharge phase of charge cycle
(typically 20% of battery capacity).
CHARGE_TERM_CURRENT
Charge termination current. The charge cycle terminates when battery
voltage is above recharge threshold, and charge current is below
this setting (typically 10% of battery capacity).
CONSTANT_CHARGE_CURRENT
constant charge current programmed by charger.
CONSTANT_CHARGE_CURRENT_MAX
maximum charge current supported by the power supply object.
CONSTANT_CHARGE_VOLTAGE
constant charge voltage programmed by charger.
CONSTANT_CHARGE_VOLTAGE_MAX
maximum charge voltage supported by the power supply object.
INPUT_CURRENT_LIMIT
input current limit programmed by charger. Indicates
the current drawn from a charging source.
CHARGE_CONTROL_LIMIT
current charge control limit setting
CHARGE_CONTROL_LIMIT_MAX
maximum charge control limit setting
CALIBRATE
battery or coulomb counter calibration status
CAPACITY
capacity in percents.
CAPACITY_ALERT_MIN
minimum capacity alert value in percents.
CAPACITY_ALERT_MAX
maximum capacity alert value in percents.
CAPACITY_LEVEL
capacity level. This corresponds to POWER_SUPPLY_CAPACITY_LEVEL_*.
TEMP
temperature of the power supply.
TEMP_ALERT_MIN
minimum battery temperature alert.
TEMP_ALERT_MAX
maximum battery temperature alert.
TEMP_AMBIENT
ambient temperature.
TEMP_AMBIENT_ALERT_MIN
minimum ambient temperature alert.
TEMP_AMBIENT_ALERT_MAX
maximum ambient temperature alert.
TEMP_MIN
minimum operatable temperature
TEMP_MAX
maximum operatable temperature
TIME_TO_EMPTY
seconds left for battery to be considered empty
(i.e. while battery powers a load)
TIME_TO_FULL
seconds left for battery to be considered full
(i.e. while battery is charging)
Battery <-> external power supply interaction
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Often power supplies are acting as supplies and supplicants at the same
time. Batteries are good example. So, batteries usually care if they're
externally powered or not.
For that case, power supply class implements notification mechanism for
batteries.
External power supply (AC) lists supplicants (batteries) names in
"supplied_to" struct member, and each power_supply_changed() call
issued by external power supply will notify supplicants via
external_power_changed callback.
Devicetree battery characteristics
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Drivers should call power_supply_get_battery_info() to obtain battery
characteristics from a devicetree battery node, defined in
Documentation/devicetree/bindings/power/supply/battery.txt. This is
implemented in drivers/power/supply/bq27xxx_battery.c.
Properties in struct power_supply_battery_info and their counterparts in the
battery node have names corresponding to elements in enum power_supply_property,
for naming consistency between sysfs attributes and battery node properties.
QA
~~
Q:
Where is POWER_SUPPLY_PROP_XYZ attribute?
A:
If you cannot find attribute suitable for your driver needs, feel free
to add it and send patch along with your driver.
The attributes available currently are the ones currently provided by the
drivers written.
Good candidates to add in future: model/part#, cycle_time, manufacturer,
etc.
Q:
I have some very specific attribute (e.g. battery color), should I add
this attribute to standard ones?
A:
Most likely, no. Such attribute can be placed in the driver itself, if
it is useful. Of course, if the attribute in question applicable to
large set of batteries, provided by many drivers, and/or comes from
some general battery specification/standard, it may be a candidate to
be added to the core attribute set.
Q:
Suppose, my battery monitoring chip/firmware does not provides capacity
in percents, but provides charge_{now,full,empty}. Should I calculate
percentage capacity manually, inside the driver, and register CAPACITY
attribute? The same question about time_to_empty/time_to_full.
A:
Most likely, no. This class is designed to export properties which are
directly measurable by the specific hardware available.
Inferring not available properties using some heuristics or mathematical
model is not subject of work for a battery driver. Such functionality
should be factored out, and in fact, apm_power, the driver to serve
legacy APM API on top of power supply class, uses a simple heuristic of
approximating remaining battery capacity based on its charge, current,
voltage and so on. But full-fledged battery model is likely not subject
for kernel at all, as it would require floating point calculation to deal
with things like differential equations and Kalman filters. This is
better be handled by batteryd/libbattery, yet to be written.

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@ -1,231 +0,0 @@
Linux power supply class
========================
Synopsis
~~~~~~~~
Power supply class used to represent battery, UPS, AC or DC power supply
properties to user-space.
It defines core set of attributes, which should be applicable to (almost)
every power supply out there. Attributes are available via sysfs and uevent
interfaces.
Each attribute has well defined meaning, up to unit of measure used. While
the attributes provided are believed to be universally applicable to any
power supply, specific monitoring hardware may not be able to provide them
all, so any of them may be skipped.
Power supply class is extensible, and allows to define drivers own attributes.
The core attribute set is subject to the standard Linux evolution (i.e.
if it will be found that some attribute is applicable to many power supply
types or their drivers, it can be added to the core set).
It also integrates with LED framework, for the purpose of providing
typically expected feedback of battery charging/fully charged status and
AC/USB power supply online status. (Note that specific details of the
indication (including whether to use it at all) are fully controllable by
user and/or specific machine defaults, per design principles of LED
framework).
Attributes/properties
~~~~~~~~~~~~~~~~~~~~~
Power supply class has predefined set of attributes, this eliminates code
duplication across drivers. Power supply class insist on reusing its
predefined attributes *and* their units.
So, userspace gets predictable set of attributes and their units for any
kind of power supply, and can process/present them to a user in consistent
manner. Results for different power supplies and machines are also directly
comparable.
See drivers/power/supply/ds2760_battery.c and drivers/power/supply/pda_power.c
for the example how to declare and handle attributes.
Units
~~~~~
Quoting include/linux/power_supply.h:
All voltages, currents, charges, energies, time and temperatures in µV,
µA, µAh, µWh, seconds and tenths of degree Celsius unless otherwise
stated. It's driver's job to convert its raw values to units in which
this class operates.
Attributes/properties detailed
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ ~ ~ ~ ~ ~ ~ Charge/Energy/Capacity - how to not confuse ~ ~ ~ ~ ~ ~ ~
~ ~
~ Because both "charge" (µAh) and "energy" (µWh) represents "capacity" ~
~ of battery, this class distinguish these terms. Don't mix them! ~
~ ~
~ CHARGE_* attributes represents capacity in µAh only. ~
~ ENERGY_* attributes represents capacity in µWh only. ~
~ CAPACITY attribute represents capacity in *percents*, from 0 to 100. ~
~ ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Postfixes:
_AVG - *hardware* averaged value, use it if your hardware is really able to
report averaged values.
_NOW - momentary/instantaneous values.
STATUS - this attribute represents operating status (charging, full,
discharging (i.e. powering a load), etc.). This corresponds to
BATTERY_STATUS_* values, as defined in battery.h.
CHARGE_TYPE - batteries can typically charge at different rates.
This defines trickle and fast charges. For batteries that
are already charged or discharging, 'n/a' can be displayed (or
'unknown', if the status is not known).
AUTHENTIC - indicates the power supply (battery or charger) connected
to the platform is authentic(1) or non authentic(0).
HEALTH - represents health of the battery, values corresponds to
POWER_SUPPLY_HEALTH_*, defined in battery.h.
VOLTAGE_OCV - open circuit voltage of the battery.
VOLTAGE_MAX_DESIGN, VOLTAGE_MIN_DESIGN - design values for maximal and
minimal power supply voltages. Maximal/minimal means values of voltages
when battery considered "full"/"empty" at normal conditions. Yes, there is
no direct relation between voltage and battery capacity, but some dumb
batteries use voltage for very approximated calculation of capacity.
Battery driver also can use this attribute just to inform userspace
about maximal and minimal voltage thresholds of a given battery.
VOLTAGE_MAX, VOLTAGE_MIN - same as _DESIGN voltage values except that
these ones should be used if hardware could only guess (measure and
retain) the thresholds of a given power supply.
VOLTAGE_BOOT - Reports the voltage measured during boot
CURRENT_BOOT - Reports the current measured during boot
CHARGE_FULL_DESIGN, CHARGE_EMPTY_DESIGN - design charge values, when
battery considered full/empty.
ENERGY_FULL_DESIGN, ENERGY_EMPTY_DESIGN - same as above but for energy.
CHARGE_FULL, CHARGE_EMPTY - These attributes means "last remembered value
of charge when battery became full/empty". It also could mean "value of
charge when battery considered full/empty at given conditions (temperature,
age)". I.e. these attributes represents real thresholds, not design values.
ENERGY_FULL, ENERGY_EMPTY - same as above but for energy.
CHARGE_COUNTER - the current charge counter (in µAh). This could easily
be negative; there is no empty or full value. It is only useful for
relative, time-based measurements.
PRECHARGE_CURRENT - the maximum charge current during precharge phase
of charge cycle (typically 20% of battery capacity).
CHARGE_TERM_CURRENT - Charge termination current. The charge cycle
terminates when battery voltage is above recharge threshold, and charge
current is below this setting (typically 10% of battery capacity).
CONSTANT_CHARGE_CURRENT - constant charge current programmed by charger.
CONSTANT_CHARGE_CURRENT_MAX - maximum charge current supported by the
power supply object.
CONSTANT_CHARGE_VOLTAGE - constant charge voltage programmed by charger.
CONSTANT_CHARGE_VOLTAGE_MAX - maximum charge voltage supported by the
power supply object.
INPUT_CURRENT_LIMIT - input current limit programmed by charger. Indicates
the current drawn from a charging source.
CHARGE_CONTROL_LIMIT - current charge control limit setting
CHARGE_CONTROL_LIMIT_MAX - maximum charge control limit setting
CALIBRATE - battery or coulomb counter calibration status
CAPACITY - capacity in percents.
CAPACITY_ALERT_MIN - minimum capacity alert value in percents.
CAPACITY_ALERT_MAX - maximum capacity alert value in percents.
CAPACITY_LEVEL - capacity level. This corresponds to
POWER_SUPPLY_CAPACITY_LEVEL_*.
TEMP - temperature of the power supply.
TEMP_ALERT_MIN - minimum battery temperature alert.
TEMP_ALERT_MAX - maximum battery temperature alert.
TEMP_AMBIENT - ambient temperature.
TEMP_AMBIENT_ALERT_MIN - minimum ambient temperature alert.
TEMP_AMBIENT_ALERT_MAX - maximum ambient temperature alert.
TEMP_MIN - minimum operatable temperature
TEMP_MAX - maximum operatable temperature
TIME_TO_EMPTY - seconds left for battery to be considered empty (i.e.
while battery powers a load)
TIME_TO_FULL - seconds left for battery to be considered full (i.e.
while battery is charging)
Battery <-> external power supply interaction
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Often power supplies are acting as supplies and supplicants at the same
time. Batteries are good example. So, batteries usually care if they're
externally powered or not.
For that case, power supply class implements notification mechanism for
batteries.
External power supply (AC) lists supplicants (batteries) names in
"supplied_to" struct member, and each power_supply_changed() call
issued by external power supply will notify supplicants via
external_power_changed callback.
Devicetree battery characteristics
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Drivers should call power_supply_get_battery_info() to obtain battery
characteristics from a devicetree battery node, defined in
Documentation/devicetree/bindings/power/supply/battery.txt. This is
implemented in drivers/power/supply/bq27xxx_battery.c.
Properties in struct power_supply_battery_info and their counterparts in the
battery node have names corresponding to elements in enum power_supply_property,
for naming consistency between sysfs attributes and battery node properties.
QA
~~
Q: Where is POWER_SUPPLY_PROP_XYZ attribute?
A: If you cannot find attribute suitable for your driver needs, feel free
to add it and send patch along with your driver.
The attributes available currently are the ones currently provided by the
drivers written.
Good candidates to add in future: model/part#, cycle_time, manufacturer,
etc.
Q: I have some very specific attribute (e.g. battery color), should I add
this attribute to standard ones?
A: Most likely, no. Such attribute can be placed in the driver itself, if
it is useful. Of course, if the attribute in question applicable to
large set of batteries, provided by many drivers, and/or comes from
some general battery specification/standard, it may be a candidate to
be added to the core attribute set.
Q: Suppose, my battery monitoring chip/firmware does not provides capacity
in percents, but provides charge_{now,full,empty}. Should I calculate
percentage capacity manually, inside the driver, and register CAPACITY
attribute? The same question about time_to_empty/time_to_full.
A: Most likely, no. This class is designed to export properties which are
directly measurable by the specific hardware available.
Inferring not available properties using some heuristics or mathematical
model is not subject of work for a battery driver. Such functionality
should be factored out, and in fact, apm_power, the driver to serve
legacy APM API on top of power supply class, uses a simple heuristic of
approximating remaining battery capacity based on its charge, current,
voltage and so on. But full-fledged battery model is likely not subject
for kernel at all, as it would require floating point calculation to deal
with things like differential equations and Kalman filters. This is
better be handled by batteryd/libbattery, yet to be written.

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=======================
Power Capping Framework
=======================
The power capping framework provides a consistent interface between the kernel
and the user space that allows power capping drivers to expose the settings to
user space in a uniform way.
Terminology
===========
The framework exposes power capping devices to user space via sysfs in the
form of a tree of objects. The objects at the root level of the tree represent
'control types', which correspond to different methods of power capping. For
example, the intel-rapl control type represents the Intel "Running Average
Power Limit" (RAPL) technology, whereas the 'idle-injection' control type
corresponds to the use of idle injection for controlling power.
Power zones represent different parts of the system, which can be controlled and
monitored using the power capping method determined by the control type the
given zone belongs to. They each contain attributes for monitoring power, as
well as controls represented in the form of power constraints. If the parts of
the system represented by different power zones are hierarchical (that is, one
bigger part consists of multiple smaller parts that each have their own power
controls), those power zones may also be organized in a hierarchy with one
parent power zone containing multiple subzones and so on to reflect the power
control topology of the system. In that case, it is possible to apply power
capping to a set of devices together using the parent power zone and if more
fine grained control is required, it can be applied through the subzones.
Example sysfs interface tree::
/sys/devices/virtual/powercap
└──intel-rapl
├──intel-rapl:0
│   ├──constraint_0_name
│   ├──constraint_0_power_limit_uw
│   ├──constraint_0_time_window_us
│   ├──constraint_1_name
│   ├──constraint_1_power_limit_uw
│   ├──constraint_1_time_window_us
│   ├──device -> ../../intel-rapl
│   ├──energy_uj
│   ├──intel-rapl:0:0
│   │   ├──constraint_0_name
│   │   ├──constraint_0_power_limit_uw
│   │   ├──constraint_0_time_window_us
│   │   ├──constraint_1_name
│   │   ├──constraint_1_power_limit_uw
│   │   ├──constraint_1_time_window_us
│   │   ├──device -> ../../intel-rapl:0
│   │   ├──energy_uj
│   │   ├──max_energy_range_uj
│   │   ├──name
│   │   ├──enabled
│   │   ├──power
│   │   │   ├──async
│   │   │   []
│   │   ├──subsystem -> ../../../../../../class/power_cap
│   │   └──uevent
│   ├──intel-rapl:0:1
│   │   ├──constraint_0_name
│   │   ├──constraint_0_power_limit_uw
│   │   ├──constraint_0_time_window_us
│   │   ├──constraint_1_name
│   │   ├──constraint_1_power_limit_uw
│   │   ├──constraint_1_time_window_us
│   │   ├──device -> ../../intel-rapl:0
│   │   ├──energy_uj
│   │   ├──max_energy_range_uj
│   │   ├──name
│   │   ├──enabled
│   │   ├──power
│   │   │   ├──async
│   │   │   []
│   │   ├──subsystem -> ../../../../../../class/power_cap
│   │   └──uevent
│   ├──max_energy_range_uj
│   ├──max_power_range_uw
│   ├──name
│   ├──enabled
│   ├──power
│   │   ├──async
│   │   []
│   ├──subsystem -> ../../../../../class/power_cap
│   ├──enabled
│   ├──uevent
├──intel-rapl:1
│   ├──constraint_0_name
│   ├──constraint_0_power_limit_uw
│   ├──constraint_0_time_window_us
│   ├──constraint_1_name
│   ├──constraint_1_power_limit_uw
│   ├──constraint_1_time_window_us
│   ├──device -> ../../intel-rapl
│   ├──energy_uj
│   ├──intel-rapl:1:0
│   │   ├──constraint_0_name
│   │   ├──constraint_0_power_limit_uw
│   │   ├──constraint_0_time_window_us
│   │   ├──constraint_1_name
│   │   ├──constraint_1_power_limit_uw
│   │   ├──constraint_1_time_window_us
│   │   ├──device -> ../../intel-rapl:1
│   │   ├──energy_uj
│   │   ├──max_energy_range_uj
│   │   ├──name
│   │   ├──enabled
│   │   ├──power
│   │   │   ├──async
│   │   │   []
│   │   ├──subsystem -> ../../../../../../class/power_cap
│   │   └──uevent
│   ├──intel-rapl:1:1
│   │   ├──constraint_0_name
│   │   ├──constraint_0_power_limit_uw
│   │   ├──constraint_0_time_window_us
│   │   ├──constraint_1_name
│   │   ├──constraint_1_power_limit_uw
│   │   ├──constraint_1_time_window_us
│   │   ├──device -> ../../intel-rapl:1
│   │   ├──energy_uj
│   │   ├──max_energy_range_uj
│   │   ├──name
│   │   ├──enabled
│   │   ├──power
│   │   │   ├──async
│   │   │   []
│   │   ├──subsystem -> ../../../../../../class/power_cap
│   │   └──uevent
│   ├──max_energy_range_uj
│   ├──max_power_range_uw
│   ├──name
│   ├──enabled
│   ├──power
│   │   ├──async
│   │   []
│   ├──subsystem -> ../../../../../class/power_cap
│   ├──uevent
├──power
│   ├──async
│   []
├──subsystem -> ../../../../class/power_cap
├──enabled
└──uevent
The above example illustrates a case in which the Intel RAPL technology,
available in Intel® IA-64 and IA-32 Processor Architectures, is used. There is one
control type called intel-rapl which contains two power zones, intel-rapl:0 and
intel-rapl:1, representing CPU packages. Each of these power zones contains
two subzones, intel-rapl:j:0 and intel-rapl:j:1 (j = 0, 1), representing the
"core" and the "uncore" parts of the given CPU package, respectively. All of
the zones and subzones contain energy monitoring attributes (energy_uj,
max_energy_range_uj) and constraint attributes (constraint_*) allowing controls
to be applied (the constraints in the 'package' power zones apply to the whole
CPU packages and the subzone constraints only apply to the respective parts of
the given package individually). Since Intel RAPL doesn't provide instantaneous
power value, there is no power_uw attribute.
In addition to that, each power zone contains a name attribute, allowing the
part of the system represented by that zone to be identified.
For example::
cat /sys/class/power_cap/intel-rapl/intel-rapl:0/name
package-0
---------
The Intel RAPL technology allows two constraints, short term and long term,
with two different time windows to be applied to each power zone. Thus for
each zone there are 2 attributes representing the constraint names, 2 power
limits and 2 attributes representing the sizes of the time windows. Such that,
constraint_j_* attributes correspond to the jth constraint (j = 0,1).
For example::
constraint_0_name
constraint_0_power_limit_uw
constraint_0_time_window_us
constraint_1_name
constraint_1_power_limit_uw
constraint_1_time_window_us
Power Zone Attributes
=====================
Monitoring attributes
---------------------
energy_uj (rw)
Current energy counter in micro joules. Write "0" to reset.
If the counter can not be reset, then this attribute is read only.
max_energy_range_uj (ro)
Range of the above energy counter in micro-joules.
power_uw (ro)
Current power in micro watts.
max_power_range_uw (ro)
Range of the above power value in micro-watts.
name (ro)
Name of this power zone.
It is possible that some domains have both power ranges and energy counter ranges;
however, only one is mandatory.
Constraints
-----------
constraint_X_power_limit_uw (rw)
Power limit in micro watts, which should be applicable for the
time window specified by "constraint_X_time_window_us".
constraint_X_time_window_us (rw)
Time window in micro seconds.
constraint_X_name (ro)
An optional name of the constraint
constraint_X_max_power_uw(ro)
Maximum allowed power in micro watts.
constraint_X_min_power_uw(ro)
Minimum allowed power in micro watts.
constraint_X_max_time_window_us(ro)
Maximum allowed time window in micro seconds.
constraint_X_min_time_window_us(ro)
Minimum allowed time window in micro seconds.
Except power_limit_uw and time_window_us other fields are optional.
Common zone and control type attributes
---------------------------------------
enabled (rw): Enable/Disable controls at zone level or for all zones using
a control type.
Power Cap Client Driver Interface
=================================
The API summary:
Call powercap_register_control_type() to register control type object.
Call powercap_register_zone() to register a power zone (under a given
control type), either as a top-level power zone or as a subzone of another
power zone registered earlier.
The number of constraints in a power zone and the corresponding callbacks have
to be defined prior to calling powercap_register_zone() to register that zone.
To Free a power zone call powercap_unregister_zone().
To free a control type object call powercap_unregister_control_type().
Detailed API can be generated using kernel-doc on include/linux/powercap.h.

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Power Capping Framework
==================================
The power capping framework provides a consistent interface between the kernel
and the user space that allows power capping drivers to expose the settings to
user space in a uniform way.
Terminology
=========================
The framework exposes power capping devices to user space via sysfs in the
form of a tree of objects. The objects at the root level of the tree represent
'control types', which correspond to different methods of power capping. For
example, the intel-rapl control type represents the Intel "Running Average
Power Limit" (RAPL) technology, whereas the 'idle-injection' control type
corresponds to the use of idle injection for controlling power.
Power zones represent different parts of the system, which can be controlled and
monitored using the power capping method determined by the control type the
given zone belongs to. They each contain attributes for monitoring power, as
well as controls represented in the form of power constraints. If the parts of
the system represented by different power zones are hierarchical (that is, one
bigger part consists of multiple smaller parts that each have their own power
controls), those power zones may also be organized in a hierarchy with one
parent power zone containing multiple subzones and so on to reflect the power
control topology of the system. In that case, it is possible to apply power
capping to a set of devices together using the parent power zone and if more
fine grained control is required, it can be applied through the subzones.
Example sysfs interface tree:
/sys/devices/virtual/powercap
??? intel-rapl
??? intel-rapl:0
?   ??? constraint_0_name
?   ??? constraint_0_power_limit_uw
?   ??? constraint_0_time_window_us
?   ??? constraint_1_name
?   ??? constraint_1_power_limit_uw
?   ??? constraint_1_time_window_us
?   ??? device -> ../../intel-rapl
?   ??? energy_uj
?   ??? intel-rapl:0:0
?   ?   ??? constraint_0_name
?   ?   ??? constraint_0_power_limit_uw
?   ?   ??? constraint_0_time_window_us
?   ?   ??? constraint_1_name
?   ?   ??? constraint_1_power_limit_uw
?   ?   ??? constraint_1_time_window_us
?   ?   ??? device -> ../../intel-rapl:0
?   ?   ??? energy_uj
?   ?   ??? max_energy_range_uj
?   ?   ??? name
?   ?   ??? enabled
?   ?   ??? power
?   ?   ?   ??? async
?   ?   ?   []
?   ?   ??? subsystem -> ../../../../../../class/power_cap
?   ?   ??? uevent
?   ??? intel-rapl:0:1
?   ?   ??? constraint_0_name
?   ?   ??? constraint_0_power_limit_uw
?   ?   ??? constraint_0_time_window_us
?   ?   ??? constraint_1_name
?   ?   ??? constraint_1_power_limit_uw
?   ?   ??? constraint_1_time_window_us
?   ?   ??? device -> ../../intel-rapl:0
?   ?   ??? energy_uj
?   ?   ??? max_energy_range_uj
?   ?   ??? name
?   ?   ??? enabled
?   ?   ??? power
?   ?   ?   ??? async
?   ?   ?   []
?   ?   ??? subsystem -> ../../../../../../class/power_cap
?   ?   ??? uevent
?   ??? max_energy_range_uj
?   ??? max_power_range_uw
?   ??? name
?   ??? enabled
?   ??? power
?   ?   ??? async
?   ?   []
?   ??? subsystem -> ../../../../../class/power_cap
?   ??? enabled
?   ??? uevent
??? intel-rapl:1
?   ??? constraint_0_name
?   ??? constraint_0_power_limit_uw
?   ??? constraint_0_time_window_us
?   ??? constraint_1_name
?   ??? constraint_1_power_limit_uw
?   ??? constraint_1_time_window_us
?   ??? device -> ../../intel-rapl
?   ??? energy_uj
?   ??? intel-rapl:1:0
?   ?   ??? constraint_0_name
?   ?   ??? constraint_0_power_limit_uw
?   ?   ??? constraint_0_time_window_us
?   ?   ??? constraint_1_name
?   ?   ??? constraint_1_power_limit_uw
?   ?   ??? constraint_1_time_window_us
?   ?   ??? device -> ../../intel-rapl:1
?   ?   ??? energy_uj
?   ?   ??? max_energy_range_uj
?   ?   ??? name
?   ?   ??? enabled
?   ?   ??? power
?   ?   ?   ??? async
?   ?   ?   []
?   ?   ??? subsystem -> ../../../../../../class/power_cap
?   ?   ??? uevent
?   ??? intel-rapl:1:1
?   ?   ??? constraint_0_name
?   ?   ??? constraint_0_power_limit_uw
?   ?   ??? constraint_0_time_window_us
?   ?   ??? constraint_1_name
?   ?   ??? constraint_1_power_limit_uw
?   ?   ??? constraint_1_time_window_us
?   ?   ??? device -> ../../intel-rapl:1
?   ?   ??? energy_uj
?   ?   ??? max_energy_range_uj
?   ?   ??? name
?   ?   ??? enabled
?   ?   ??? power
?   ?   ?   ??? async
?   ?   ?   []
?   ?   ??? subsystem -> ../../../../../../class/power_cap
?   ?   ??? uevent
?   ??? max_energy_range_uj
?   ??? max_power_range_uw
?   ??? name
?   ??? enabled
?   ??? power
?   ?   ??? async
?   ?   []
?   ??? subsystem -> ../../../../../class/power_cap
?   ??? uevent
??? power
?   ??? async
?   []
??? subsystem -> ../../../../class/power_cap
??? enabled
??? uevent
The above example illustrates a case in which the Intel RAPL technology,
available in Intel® IA-64 and IA-32 Processor Architectures, is used. There is one
control type called intel-rapl which contains two power zones, intel-rapl:0 and
intel-rapl:1, representing CPU packages. Each of these power zones contains
two subzones, intel-rapl:j:0 and intel-rapl:j:1 (j = 0, 1), representing the
"core" and the "uncore" parts of the given CPU package, respectively. All of
the zones and subzones contain energy monitoring attributes (energy_uj,
max_energy_range_uj) and constraint attributes (constraint_*) allowing controls
to be applied (the constraints in the 'package' power zones apply to the whole
CPU packages and the subzone constraints only apply to the respective parts of
the given package individually). Since Intel RAPL doesn't provide instantaneous
power value, there is no power_uw attribute.
In addition to that, each power zone contains a name attribute, allowing the
part of the system represented by that zone to be identified.
For example:
cat /sys/class/power_cap/intel-rapl/intel-rapl:0/name
package-0
The Intel RAPL technology allows two constraints, short term and long term,
with two different time windows to be applied to each power zone. Thus for
each zone there are 2 attributes representing the constraint names, 2 power
limits and 2 attributes representing the sizes of the time windows. Such that,
constraint_j_* attributes correspond to the jth constraint (j = 0,1).
For example:
constraint_0_name
constraint_0_power_limit_uw
constraint_0_time_window_us
constraint_1_name
constraint_1_power_limit_uw
constraint_1_time_window_us
Power Zone Attributes
=================================
Monitoring attributes
----------------------
energy_uj (rw): Current energy counter in micro joules. Write "0" to reset.
If the counter can not be reset, then this attribute is read only.
max_energy_range_uj (ro): Range of the above energy counter in micro-joules.
power_uw (ro): Current power in micro watts.
max_power_range_uw (ro): Range of the above power value in micro-watts.
name (ro): Name of this power zone.
It is possible that some domains have both power ranges and energy counter ranges;
however, only one is mandatory.
Constraints
----------------
constraint_X_power_limit_uw (rw): Power limit in micro watts, which should be
applicable for the time window specified by "constraint_X_time_window_us".
constraint_X_time_window_us (rw): Time window in micro seconds.
constraint_X_name (ro): An optional name of the constraint
constraint_X_max_power_uw(ro): Maximum allowed power in micro watts.
constraint_X_min_power_uw(ro): Minimum allowed power in micro watts.
constraint_X_max_time_window_us(ro): Maximum allowed time window in micro seconds.
constraint_X_min_time_window_us(ro): Minimum allowed time window in micro seconds.
Except power_limit_uw and time_window_us other fields are optional.
Common zone and control type attributes
----------------------------------------
enabled (rw): Enable/Disable controls at zone level or for all zones using
a control type.
Power Cap Client Driver Interface
==================================
The API summary:
Call powercap_register_control_type() to register control type object.
Call powercap_register_zone() to register a power zone (under a given
control type), either as a top-level power zone or as a subzone of another
power zone registered earlier.
The number of constraints in a power zone and the corresponding callbacks have
to be defined prior to calling powercap_register_zone() to register that zone.
To Free a power zone call powercap_unregister_zone().
To free a control type object call powercap_unregister_control_type().
Detailed API can be generated using kernel-doc on include/linux/powercap.h.

141
Documentation/power/regulator/consumer.txt → Documentation/power/regulator/consumer.rst
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@ -1,3 +1,4 @@
===================================
Regulator Consumer Driver Interface
===================================
@ -8,73 +9,77 @@ Please see overview.txt for a description of the terms used in this text.
1. Consumer Regulator Access (static & dynamic drivers)
=======================================================
A consumer driver can get access to its supply regulator by calling :-
A consumer driver can get access to its supply regulator by calling ::
regulator = regulator_get(dev, "Vcc");
regulator = regulator_get(dev, "Vcc");
The consumer passes in its struct device pointer and power supply ID. The core
then finds the correct regulator by consulting a machine specific lookup table.
If the lookup is successful then this call will return a pointer to the struct
regulator that supplies this consumer.
To release the regulator the consumer driver should call :-
To release the regulator the consumer driver should call ::
regulator_put(regulator);
regulator_put(regulator);
Consumers can be supplied by more than one regulator e.g. codec consumer with
analog and digital supplies :-
analog and digital supplies ::
digital = regulator_get(dev, "Vcc"); /* digital core */
analog = regulator_get(dev, "Avdd"); /* analog */
digital = regulator_get(dev, "Vcc"); /* digital core */
analog = regulator_get(dev, "Avdd"); /* analog */
The regulator access functions regulator_get() and regulator_put() will
usually be called in your device drivers probe() and remove() respectively.
2. Regulator Output Enable & Disable (static & dynamic drivers)
====================================================================
===============================================================
A consumer can enable its power supply by calling:-
int regulator_enable(regulator);
A consumer can enable its power supply by calling::
NOTE: The supply may already be enabled before regulator_enabled() is called.
This may happen if the consumer shares the regulator or the regulator has been
previously enabled by bootloader or kernel board initialization code.
int regulator_enable(regulator);
A consumer can determine if a regulator is enabled by calling :-
NOTE:
The supply may already be enabled before regulator_enabled() is called.
This may happen if the consumer shares the regulator or the regulator has been
previously enabled by bootloader or kernel board initialization code.
int regulator_is_enabled(regulator);
A consumer can determine if a regulator is enabled by calling::
int regulator_is_enabled(regulator);
This will return > zero when the regulator is enabled.
A consumer can disable its supply when no longer needed by calling :-
A consumer can disable its supply when no longer needed by calling::
int regulator_disable(regulator);
int regulator_disable(regulator);
NOTE: This may not disable the supply if it's shared with other consumers. The
regulator will only be disabled when the enabled reference count is zero.
NOTE:
This may not disable the supply if it's shared with other consumers. The
regulator will only be disabled when the enabled reference count is zero.
Finally, a regulator can be forcefully disabled in the case of an emergency :-
Finally, a regulator can be forcefully disabled in the case of an emergency::
int regulator_force_disable(regulator);
int regulator_force_disable(regulator);
NOTE: this will immediately and forcefully shutdown the regulator output. All
consumers will be powered off.
NOTE:
this will immediately and forcefully shutdown the regulator output. All
consumers will be powered off.
3. Regulator Voltage Control & Status (dynamic drivers)
======================================================
=======================================================
Some consumer drivers need to be able to dynamically change their supply
voltage to match system operating points. e.g. CPUfreq drivers can scale
voltage along with frequency to save power, SD drivers may need to select the
correct card voltage, etc.
Consumers can control their supply voltage by calling :-
Consumers can control their supply voltage by calling::
int regulator_set_voltage(regulator, min_uV, max_uV);
int regulator_set_voltage(regulator, min_uV, max_uV);
Where min_uV and max_uV are the minimum and maximum acceptable voltages in
microvolts.
@ -84,47 +89,50 @@ when enabled, then the voltage changes instantly, otherwise the voltage
configuration changes and the voltage is physically set when the regulator is
next enabled.
The regulators configured voltage output can be found by calling :-
The regulators configured voltage output can be found by calling::
int regulator_get_voltage(regulator);
int regulator_get_voltage(regulator);
NOTE: get_voltage() will return the configured output voltage whether the
regulator is enabled or disabled and should NOT be used to determine regulator
output state. However this can be used in conjunction with is_enabled() to
determine the regulator physical output voltage.
NOTE:
get_voltage() will return the configured output voltage whether the
regulator is enabled or disabled and should NOT be used to determine regulator
output state. However this can be used in conjunction with is_enabled() to
determine the regulator physical output voltage.
4. Regulator Current Limit Control & Status (dynamic drivers)
===========================================================
=============================================================
Some consumer drivers need to be able to dynamically change their supply
current limit to match system operating points. e.g. LCD backlight driver can
change the current limit to vary the backlight brightness, USB drivers may want
to set the limit to 500mA when supplying power.
Consumers can control their supply current limit by calling :-
Consumers can control their supply current limit by calling::
int regulator_set_current_limit(regulator, min_uA, max_uA);
int regulator_set_current_limit(regulator, min_uA, max_uA);
Where min_uA and max_uA are the minimum and maximum acceptable current limit in
microamps.
NOTE: this can be called when the regulator is enabled or disabled. If called
when enabled, then the current limit changes instantly, otherwise the current
limit configuration changes and the current limit is physically set when the
regulator is next enabled.
NOTE:
this can be called when the regulator is enabled or disabled. If called
when enabled, then the current limit changes instantly, otherwise the current
limit configuration changes and the current limit is physically set when the
regulator is next enabled.
A regulators current limit can be found by calling :-
A regulators current limit can be found by calling::
int regulator_get_current_limit(regulator);
int regulator_get_current_limit(regulator);
NOTE: get_current_limit() will return the current limit whether the regulator
is enabled or disabled and should not be used to determine regulator current
load.
NOTE:
get_current_limit() will return the current limit whether the regulator
is enabled or disabled and should not be used to determine regulator current
load.
5. Regulator Operating Mode Control & Status (dynamic drivers)
=============================================================
==============================================================
Some consumers can further save system power by changing the operating mode of
their supply regulator to be more efficient when the consumers operating state
@ -135,9 +143,9 @@ Regulator operating mode can be changed indirectly or directly.
Indirect operating mode control.
--------------------------------
Consumer drivers can request a change in their supply regulator operating mode
by calling :-
by calling::
int regulator_set_load(struct regulator *regulator, int load_uA);
int regulator_set_load(struct regulator *regulator, int load_uA);
This will cause the core to recalculate the total load on the regulator (based
on all its consumers) and change operating mode (if necessary and permitted)
@ -153,12 +161,13 @@ consumers.
Direct operating mode control.
------------------------------
Bespoke or tightly coupled drivers may want to directly control regulator
operating mode depending on their operating point. This can be achieved by
calling :-
calling::
int regulator_set_mode(struct regulator *regulator, unsigned int mode);
unsigned int regulator_get_mode(struct regulator *regulator);
int regulator_set_mode(struct regulator *regulator, unsigned int mode);
unsigned int regulator_get_mode(struct regulator *regulator);
Direct mode will only be used by consumers that *know* about the regulator and
are not sharing the regulator with other consumers.
@ -166,24 +175,26 @@ are not sharing the regulator with other consumers.
6. Regulator Events
===================
Regulators can notify consumers of external events. Events could be received by
consumers under regulator stress or failure conditions.
Consumers can register interest in regulator events by calling :-
Consumers can register interest in regulator events by calling::
int regulator_register_notifier(struct regulator *regulator,
struct notifier_block *nb);
int regulator_register_notifier(struct regulator *regulator,
struct notifier_block *nb);
Consumers can unregister interest by calling :-
Consumers can unregister interest by calling::
int regulator_unregister_notifier(struct regulator *regulator,
struct notifier_block *nb);
int regulator_unregister_notifier(struct regulator *regulator,
struct notifier_block *nb);
Regulators use the kernel notifier framework to send event to their interested
consumers.
7. Regulator Direct Register Access
===================================
Some kinds of power management hardware or firmware are designed such that
they need to do low-level hardware access to regulators, with no involvement
from the kernel. Examples of such devices are:
@ -199,20 +210,20 @@ to it. The regulator framework provides the following helpers for querying
these details.
Bus-specific details, like I2C addresses or transfer rates are handled by the
regmap framework. To get the regulator's regmap (if supported), use :-
regmap framework. To get the regulator's regmap (if supported), use::
struct regmap *regulator_get_regmap(struct regulator *regulator);
struct regmap *regulator_get_regmap(struct regulator *regulator);
To obtain the hardware register offset and bitmask for the regulator's voltage
selector register, use :-
selector register, use::
int regulator_get_hardware_vsel_register(struct regulator *regulator,
unsigned *vsel_reg,
unsigned *vsel_mask);
int regulator_get_hardware_vsel_register(struct regulator *regulator,
unsigned *vsel_reg,
unsigned *vsel_mask);
To convert a regulator framework voltage selector code (used by
regulator_list_voltage) to a hardware-specific voltage selector that can be
directly written to the voltage selector register, use :-
directly written to the voltage selector register, use::
int regulator_list_hardware_vsel(struct regulator *regulator,
unsigned selector);
int regulator_list_hardware_vsel(struct regulator *regulator,
unsigned selector);

9
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@ -1,3 +1,4 @@
==========================
Regulator API design notes
==========================
@ -14,7 +15,9 @@ Safety
have different power requirements, and not all components with power
requirements are visible to software.
=> The API should make no changes to the hardware state unless it has
.. note::
The API should make no changes to the hardware state unless it has
specific knowledge that these changes are safe to perform on this
particular system.
@ -28,6 +31,8 @@ Consumer use cases
- Many of the power supplies in the system will be shared between many
different consumers.
=> The consumer API should be structured so that these use cases are
.. note::
The consumer API should be structured so that these use cases are
very easy to handle and so that consumers will work with shared
supplies without any additional effort.

47
Documentation/power/regulator/machine.txt → Documentation/power/regulator/machine.rst
View File

@ -1,10 +1,11 @@
==================================
Regulator Machine Driver Interface
===================================
==================================
The regulator machine driver interface is intended for board/machine specific
initialisation code to configure the regulator subsystem.
Consider the following machine :-
Consider the following machine::
Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
|
@ -13,31 +14,31 @@ Consider the following machine :-
The drivers for consumers A & B must be mapped to the correct regulator in
order to control their power supplies. This mapping can be achieved in machine
initialisation code by creating a struct regulator_consumer_supply for
each regulator.
each regulator::
struct regulator_consumer_supply {
struct regulator_consumer_supply {
const char *dev_name; /* consumer dev_name() */
const char *supply; /* consumer supply - e.g. "vcc" */
};
};
e.g. for the machine above
e.g. for the machine above::
static struct regulator_consumer_supply regulator1_consumers[] = {
static struct regulator_consumer_supply regulator1_consumers[] = {
REGULATOR_SUPPLY("Vcc", "consumer B"),
};
};
static struct regulator_consumer_supply regulator2_consumers[] = {
static struct regulator_consumer_supply regulator2_consumers[] = {
REGULATOR_SUPPLY("Vcc", "consumer A"),
};
};
This maps Regulator-1 to the 'Vcc' supply for Consumer B and maps Regulator-2
to the 'Vcc' supply for Consumer A.
Constraints can now be registered by defining a struct regulator_init_data
for each regulator power domain. This structure also maps the consumers
to their supply regulators :-
to their supply regulators::
static struct regulator_init_data regulator1_data = {
static struct regulator_init_data regulator1_data = {
.constraints = {
.name = "Regulator-1",
.min_uV = 3300000,
@ -46,7 +47,7 @@ static struct regulator_init_data regulator1_data = {
},
.num_consumer_supplies = ARRAY_SIZE(regulator1_consumers),
.consumer_supplies = regulator1_consumers,
};
};
The name field should be set to something that is usefully descriptive
for the board for configuration of supplies for other regulators and
@ -57,9 +58,9 @@ name is provided then the subsystem will choose one.
Regulator-1 supplies power to Regulator-2. This relationship must be registered
with the core so that Regulator-1 is also enabled when Consumer A enables its
supply (Regulator-2). The supply regulator is set by the supply_regulator
field below and co:-
field below and co::
static struct regulator_init_data regulator2_data = {
static struct regulator_init_data regulator2_data = {
.supply_regulator = "Regulator-1",
.constraints = {
.min_uV = 1800000,
@ -69,11 +70,11 @@ static struct regulator_init_data regulator2_data = {
},
.num_consumer_supplies = ARRAY_SIZE(regulator2_consumers),
.consumer_supplies = regulator2_consumers,
};
};
Finally the regulator devices must be registered in the usual manner.
Finally the regulator devices must be registered in the usual manner::
static struct platform_device regulator_devices[] = {
static struct platform_device regulator_devices[] = {
{
.name = "regulator",
.id = DCDC_1,
@ -88,9 +89,9 @@ static struct platform_device regulator_devices[] = {
.platform_data = &regulator2_data,
},
},
};
/* register regulator 1 device */
platform_device_register(&regulator_devices[0]);
};
/* register regulator 1 device */
platform_device_register(&regulator_devices[0]);
/* register regulator 2 device */
platform_device_register(&regulator_devices[1]);
/* register regulator 2 device */
platform_device_register(&regulator_devices[1]);

57
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@ -1,3 +1,4 @@
=============================================
Linux voltage and current regulator framework
=============================================
@ -13,26 +14,30 @@ regulators (where voltage output is controllable) and current sinks (where
current limit is controllable).
(C) 2008 Wolfson Microelectronics PLC.
Author: Liam Girdwood <lrg@slimlogic.co.uk>
Nomenclature
============
Some terms used in this document:-
Some terms used in this document:
o Regulator - Electronic device that supplies power to other devices.
- Regulator
- Electronic device that supplies power to other devices.
Most regulators can enable and disable their output while
some can control their output voltage and or current.
Input Voltage -> Regulator -> Output Voltage
o PMIC - Power Management IC. An IC that contains numerous regulators
and often contains other subsystems.
- PMIC
- Power Management IC. An IC that contains numerous
regulators and often contains other subsystems.
o Consumer - Electronic device that is supplied power by a regulator.
- Consumer
- Electronic device that is supplied power by a regulator.
Consumers can be classified into two types:-
Static: consumer does not change its supply voltage or
@ -44,46 +49,48 @@ Some terms used in this document:-
current limit to meet operation demands.
o Power Domain - Electronic circuit that is supplied its input power by the
- Power Domain
- Electronic circuit that is supplied its input power by the
output power of a regulator, switch or by another power
domain.
The supply regulator may be behind a switch(s). i.e.
The supply regulator may be behind a switch(s). i.e.::
Regulator -+-> Switch-1 -+-> Switch-2 --> [Consumer A]
| |
| +-> [Consumer B], [Consumer C]
|
+-> [Consumer D], [Consumer E]
Regulator -+-> Switch-1 -+-> Switch-2 --> [Consumer A]
| |
| +-> [Consumer B], [Consumer C]
|
+-> [Consumer D], [Consumer E]
That is one regulator and three power domains:
Domain 1: Switch-1, Consumers D & E.
Domain 2: Switch-2, Consumers B & C.
Domain 3: Consumer A.
- Domain 1: Switch-1, Consumers D & E.
- Domain 2: Switch-2, Consumers B & C.
- Domain 3: Consumer A.
and this represents a "supplies" relationship:
Domain-1 --> Domain-2 --> Domain-3.
A power domain may have regulators that are supplied power
by other regulators. i.e.
by other regulators. i.e.::
Regulator-1 -+-> Regulator-2 -+-> [Consumer A]
|
+-> [Consumer B]
Regulator-1 -+-> Regulator-2 -+-> [Consumer A]
|
+-> [Consumer B]
This gives us two regulators and two power domains:
Domain 1: Regulator-2, Consumer B.
Domain 2: Consumer A.
- Domain 1: Regulator-2, Consumer B.
- Domain 2: Consumer A.
and a "supplies" relationship:
Domain-1 --> Domain-2
o Constraints - Constraints are used to define power levels for performance
- Constraints
- Constraints are used to define power levels for performance
and hardware protection. Constraints exist at three levels:
Regulator Level: This is defined by the regulator hardware
@ -141,7 +148,7 @@ relevant to non SoC devices and is split into the following four interfaces:-
limit. This also compiles out if not in use so drivers can be reused in
systems with no regulator based power control.
See Documentation/power/regulator/consumer.txt
See Documentation/power/regulator/consumer.rst
2. Regulator driver interface.
@ -149,7 +156,7 @@ relevant to non SoC devices and is split into the following four interfaces:-
operations to the core. It also has a notifier call chain for propagating
regulator events to clients.
See Documentation/power/regulator/regulator.txt
See Documentation/power/regulator/regulator.rst
3. Machine interface.
@ -160,7 +167,7 @@ relevant to non SoC devices and is split into the following four interfaces:-
allows the creation of a regulator tree whereby some regulators are
supplied by others (similar to a clock tree).
See Documentation/power/regulator/machine.txt
See Documentation/power/regulator/machine.rst
4. Userspace ABI.

32
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@ -0,0 +1,32 @@
==========================
Regulator Driver Interface
==========================
The regulator driver interface is relatively simple and designed to allow
regulator drivers to register their services with the core framework.
Registration
============
Drivers can register a regulator by calling::
struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
const struct regulator_config *config);
This will register the regulator's capabilities and operations to the regulator
core.
Regulators can be unregistered by calling::
void regulator_unregister(struct regulator_dev *rdev);
Regulator Events
================
Regulators can send events (e.g. overtemperature, undervoltage, etc) to
consumer drivers by calling::
int regulator_notifier_call_chain(struct regulator_dev *rdev,
unsigned long event, void *data);

30
Documentation/power/regulator/regulator.txt
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@ -1,30 +0,0 @@
Regulator Driver Interface
==========================
The regulator driver interface is relatively simple and designed to allow
regulator drivers to register their services with the core framework.
Registration
============
Drivers can register a regulator by calling :-
struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
const struct regulator_config *config);
This will register the regulator's capabilities and operations to the regulator
core.
Regulators can be unregistered by calling :-
void regulator_unregister(struct regulator_dev *rdev);
Regulator Events
================
Regulators can send events (e.g. overtemperature, undervoltage, etc) to
consumer drivers by calling :-
int regulator_notifier_call_chain(struct regulator_dev *rdev,
unsigned long event, void *data);

234
Documentation/power/runtime_pm.txt → Documentation/power/runtime_pm.rst
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@ -1,10 +1,15 @@
==================================================
Runtime Power Management Framework for I/O Devices
==================================================
(C) 2009-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
(C) 2010 Alan Stern <stern@rowland.harvard.edu>
(C) 2014 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
1. Introduction
===============
Support for runtime power management (runtime PM) of I/O devices is provided
at the power management core (PM core) level by means of:
@ -33,16 +38,17 @@ fields of 'struct dev_pm_info' and the core helper functions provided for
runtime PM are described below.
2. Device Runtime PM Callbacks
==============================
There are three device runtime PM callbacks defined in 'struct dev_pm_ops':
There are three device runtime PM callbacks defined in 'struct dev_pm_ops'::
struct dev_pm_ops {
struct dev_pm_ops {
...
int (*runtime_suspend)(struct device *dev);
int (*runtime_resume)(struct device *dev);
int (*runtime_idle)(struct device *dev);
...
};
};
The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks
are executed by the PM core for the device's subsystem that may be either of
@ -112,7 +118,7 @@ low-power state during the execution of the suspend callback, it is expected
that remote wakeup will be enabled for the device. Generally, remote wakeup
should be enabled for all input devices put into low-power states at run time.
The subsystem-level resume callback, if present, is _entirely_ _responsible_ for
The subsystem-level resume callback, if present, is **entirely responsible** for
handling the resume of the device as appropriate, which may, but need not
include executing the device driver's own ->runtime_resume() callback (from the
PM core's point of view it is not necessary to implement a ->runtime_resume()
@ -197,95 +203,96 @@ rules:
except for scheduled autosuspends.
3. Runtime PM Device Fields
===========================
The following device runtime PM fields are present in 'struct dev_pm_info', as
defined in include/linux/pm.h:
struct timer_list suspend_timer;
`struct timer_list suspend_timer;`
- timer used for scheduling (delayed) suspend and autosuspend requests
unsigned long timer_expires;
`unsigned long timer_expires;`
- timer expiration time, in jiffies (if this is different from zero, the
timer is running and will expire at that time, otherwise the timer is not
running)
struct work_struct work;
`struct work_struct work;`
- work structure used for queuing up requests (i.e. work items in pm_wq)
wait_queue_head_t wait_queue;
`wait_queue_head_t wait_queue;`
- wait queue used if any of the helper functions needs to wait for another
one to complete
spinlock_t lock;
`spinlock_t lock;`
- lock used for synchronization
atomic_t usage_count;
`atomic_t usage_count;`
- the usage counter of the device
atomic_t child_count;
`atomic_t child_count;`
- the count of 'active' children of the device
unsigned int ignore_children;
`unsigned int ignore_children;`
- if set, the value of child_count is ignored (but still updated)
unsigned int disable_depth;
`unsigned int disable_depth;`
- used for disabling the helper functions (they work normally if this is
equal to zero); the initial value of it is 1 (i.e. runtime PM is
initially disabled for all devices)
int runtime_error;
`int runtime_error;`
- if set, there was a fatal error (one of the callbacks returned error code
as described in Section 2), so the helper functions will not work until
this flag is cleared; this is the error code returned by the failing
callback
unsigned int idle_notification;
`unsigned int idle_notification;`
- if set, ->runtime_idle() is being executed
unsigned int request_pending;
`unsigned int request_pending;`
- if set, there's a pending request (i.e. a work item queued up into pm_wq)
enum rpm_request request;
`enum rpm_request request;`
- type of request that's pending (valid if request_pending is set)
unsigned int deferred_resume;
`unsigned int deferred_resume;`
- set if ->runtime_resume() is about to be run while ->runtime_suspend() is
being executed for that device and it is not practical to wait for the
suspend to complete; means "start a resume as soon as you've suspended"
enum rpm_status runtime_status;
`enum rpm_status runtime_status;`
- the runtime PM status of the device; this field's initial value is
RPM_SUSPENDED, which means that each device is initially regarded by the
PM core as 'suspended', regardless of its real hardware status
unsigned int runtime_auto;
`unsigned int runtime_auto;`
- if set, indicates that the user space has allowed the device driver to
power manage the device at run time via the /sys/devices/.../power/control
interface; it may only be modified with the help of the pm_runtime_allow()
`interface;` it may only be modified with the help of the pm_runtime_allow()
and pm_runtime_forbid() helper functions
unsigned int no_callbacks;
`unsigned int no_callbacks;`
- indicates that the device does not use the runtime PM callbacks (see
Section 8); it may be modified only by the pm_runtime_no_callbacks()
helper function
unsigned int irq_safe;
`unsigned int irq_safe;`
- indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
will be invoked with the spinlock held and interrupts disabled
unsigned int use_autosuspend;
`unsigned int use_autosuspend;`
- indicates that the device's driver supports delayed autosuspend (see
Section 9); it may be modified only by the
pm_runtime{_dont}_use_autosuspend() helper functions
unsigned int timer_autosuspends;
`unsigned int timer_autosuspends;`
- indicates that the PM core should attempt to carry out an autosuspend
when the timer expires rather than a normal suspend
int autosuspend_delay;
`int autosuspend_delay;`
- the delay time (in milliseconds) to be used for autosuspend
unsigned long last_busy;
`unsigned long last_busy;`
- the time (in jiffies) when the pm_runtime_mark_last_busy() helper
function was last called for this device; used in calculating inactivity
periods for autosuspend
@ -293,37 +300,38 @@ defined in include/linux/pm.h:
All of the above fields are members of the 'power' member of 'struct device'.
4. Runtime PM Device Helper Functions
=====================================
The following runtime PM helper functions are defined in
drivers/base/power/runtime.c and include/linux/pm_runtime.h:
void pm_runtime_init(struct device *dev);
`void pm_runtime_init(struct device *dev);`
- initialize the device runtime PM fields in 'struct dev_pm_info'
void pm_runtime_remove(struct device *dev);
`void pm_runtime_remove(struct device *dev);`
- make sure that the runtime PM of the device will be disabled after
removing the device from device hierarchy
int pm_runtime_idle(struct device *dev);
`int pm_runtime_idle(struct device *dev);`
- execute the subsystem-level idle callback for the device; returns an
error code on failure, where -EINPROGRESS means that ->runtime_idle() is
already being executed; if there is no callback or the callback returns 0
then run pm_runtime_autosuspend(dev) and return its result
int pm_runtime_suspend(struct device *dev);
`int pm_runtime_suspend(struct device *dev);`
- execute the subsystem-level suspend callback for the device; returns 0 on
success, 1 if the device's runtime PM status was already 'suspended', or
error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt
to suspend the device again in future and -EACCES means that
'power.disable_depth' is different from 0
int pm_runtime_autosuspend(struct device *dev);
`int pm_runtime_autosuspend(struct device *dev);`
- same as pm_runtime_suspend() except that the autosuspend delay is taken
into account; if pm_runtime_autosuspend_expiration() says the delay has
`into account;` if pm_runtime_autosuspend_expiration() says the delay has
not yet expired then an autosuspend is scheduled for the appropriate time
and 0 is returned
int pm_runtime_resume(struct device *dev);
`int pm_runtime_resume(struct device *dev);`
- execute the subsystem-level resume callback for the device; returns 0 on
success, 1 if the device's runtime PM status was already 'active' or
error code on failure, where -EAGAIN means it may be safe to attempt to
@ -331,17 +339,17 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
checked additionally, and -EACCES means that 'power.disable_depth' is
different from 0
int pm_request_idle(struct device *dev);
`int pm_request_idle(struct device *dev);`
- submit a request to execute the subsystem-level idle callback for the
device (the request is represented by a work item in pm_wq); returns 0 on
success or error code if the request has not been queued up
int pm_request_autosuspend(struct device *dev);
`int pm_request_autosuspend(struct device *dev);`
- schedule the execution of the subsystem-level suspend callback for the
device when the autosuspend delay has expired; if the delay has already
expired then the work item is queued up immediately
int pm_schedule_suspend(struct device *dev, unsigned int delay);
`int pm_schedule_suspend(struct device *dev, unsigned int delay);`
- schedule the execution of the subsystem-level suspend callback for the
device in future, where 'delay' is the time to wait before queuing up a
suspend work item in pm_wq, in milliseconds (if 'delay' is zero, the work
@ -351,58 +359,58 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
->runtime_suspend() is already scheduled and not yet expired, the new
value of 'delay' will be used as the time to wait
int pm_request_resume(struct device *dev);
`int pm_request_resume(struct device *dev);`
- submit a request to execute the subsystem-level resume callback for the
device (the request is represented by a work item in pm_wq); returns 0 on
success, 1 if the device's runtime PM status was already 'active', or
error code if the request hasn't been queued up
void pm_runtime_get_noresume(struct device *dev);
`void pm_runtime_get_noresume(struct device *dev);`
- increment the device's usage counter
int pm_runtime_get(struct device *dev);
`int pm_runtime_get(struct device *dev);`
- increment the device's usage counter, run pm_request_resume(dev) and
return its result
int pm_runtime_get_sync(struct device *dev);
`int pm_runtime_get_sync(struct device *dev);`
- increment the device's usage counter, run pm_runtime_resume(dev) and
return its result
int pm_runtime_get_if_in_use(struct device *dev);
`int pm_runtime_get_if_in_use(struct device *dev);`
- return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
nonzero, increment the counter and return 1; otherwise return 0 without
changing the counter
void pm_runtime_put_noidle(struct device *dev);
`void pm_runtime_put_noidle(struct device *dev);`
- decrement the device's usage counter
int pm_runtime_put(struct device *dev);
`int pm_runtime_put(struct device *dev);`
- decrement the device's usage counter; if the result is 0 then run
pm_request_idle(dev) and return its result
int pm_runtime_put_autosuspend(struct device *dev);
`int pm_runtime_put_autosuspend(struct device *dev);`
- decrement the device's usage counter; if the result is 0 then run
pm_request_autosuspend(dev) and return its result
int pm_runtime_put_sync(struct device *dev);
`int pm_runtime_put_sync(struct device *dev);`
- decrement the device's usage counter; if the result is 0 then run
pm_runtime_idle(dev) and return its result
int pm_runtime_put_sync_suspend(struct device *dev);
`int pm_runtime_put_sync_suspend(struct device *dev);`
- decrement the device's usage counter; if the result is 0 then run
pm_runtime_suspend(dev) and return its result
int pm_runtime_put_sync_autosuspend(struct device *dev);
`int pm_runtime_put_sync_autosuspend(struct device *dev);`
- decrement the device's usage counter; if the result is 0 then run
pm_runtime_autosuspend(dev) and return its result
void pm_runtime_enable(struct device *dev);
`void pm_runtime_enable(struct device *dev);`
- decrement the device's 'power.disable_depth' field; if that field is equal
to zero, the runtime PM helper functions can execute subsystem-level
callbacks described in Section 2 for the device
int pm_runtime_disable(struct device *dev);
`int pm_runtime_disable(struct device *dev);`
- increment the device's 'power.disable_depth' field (if the value of that
field was previously zero, this prevents subsystem-level runtime PM
callbacks from being run for the device), make sure that all of the
@ -411,7 +419,7 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
necessary to execute the subsystem-level resume callback for the device
to satisfy that request, otherwise 0 is returned
int pm_runtime_barrier(struct device *dev);
`int pm_runtime_barrier(struct device *dev);`
- check if there's a resume request pending for the device and resume it
(synchronously) in that case, cancel any other pending runtime PM requests
regarding it and wait for all runtime PM operations on it in progress to
@ -419,10 +427,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
necessary to execute the subsystem-level resume callback for the device to
satisfy that request, otherwise 0 is returned
void pm_suspend_ignore_children(struct device *dev, bool enable);
`void pm_suspend_ignore_children(struct device *dev, bool enable);`
- set/unset the power.ignore_children flag of the device
int pm_runtime_set_active(struct device *dev);
`int pm_runtime_set_active(struct device *dev);`
- clear the device's 'power.runtime_error' flag, set the device's runtime
PM status to 'active' and update its parent's counter of 'active'
children as appropriate (it is only valid to use this function if
@ -430,61 +438,61 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
zero); it will fail and return error code if the device has a parent
which is not active and the 'power.ignore_children' flag of which is unset
void pm_runtime_set_suspended(struct device *dev);
`void pm_runtime_set_suspended(struct device *dev);`
- clear the device's 'power.runtime_error' flag, set the device's runtime
PM status to 'suspended' and update its parent's counter of 'active'
children as appropriate (it is only valid to use this function if
'power.runtime_error' is set or 'power.disable_depth' is greater than
zero)
bool pm_runtime_active(struct device *dev);
`bool pm_runtime_active(struct device *dev);`
- return true if the device's runtime PM status is 'active' or its
'power.disable_depth' field is not equal to zero, or false otherwise
bool pm_runtime_suspended(struct device *dev);
`bool pm_runtime_suspended(struct device *dev);`
- return true if the device's runtime PM status is 'suspended' and its
'power.disable_depth' field is equal to zero, or false otherwise
bool pm_runtime_status_suspended(struct device *dev);
`bool pm_runtime_status_suspended(struct device *dev);`
- return true if the device's runtime PM status is 'suspended'
void pm_runtime_allow(struct device *dev);
`void pm_runtime_allow(struct device *dev);`
- set the power.runtime_auto flag for the device and decrease its usage
counter (used by the /sys/devices/.../power/control interface to
effectively allow the device to be power managed at run time)
void pm_runtime_forbid(struct device *dev);
`void pm_runtime_forbid(struct device *dev);`
- unset the power.runtime_auto flag for the device and increase its usage
counter (used by the /sys/devices/.../power/control interface to
effectively prevent the device from being power managed at run time)
void pm_runtime_no_callbacks(struct device *dev);
`void pm_runtime_no_callbacks(struct device *dev);`
- set the power.no_callbacks flag for the device and remove the runtime
PM attributes from /sys/devices/.../power (or prevent them from being
added when the device is registered)
void pm_runtime_irq_safe(struct device *dev);
`void pm_runtime_irq_safe(struct device *dev);`
- set the power.irq_safe flag for the device, causing the runtime-PM
callbacks to be invoked with interrupts off
bool pm_runtime_is_irq_safe(struct device *dev);
`bool pm_runtime_is_irq_safe(struct device *dev);`
- return true if power.irq_safe flag was set for the device, causing
the runtime-PM callbacks to be invoked with interrupts off
void pm_runtime_mark_last_busy(struct device *dev);
`void pm_runtime_mark_last_busy(struct device *dev);`
- set the power.last_busy field to the current time
void pm_runtime_use_autosuspend(struct device *dev);
`void pm_runtime_use_autosuspend(struct device *dev);`
- set the power.use_autosuspend flag, enabling autosuspend delays; call
pm_runtime_get_sync if the flag was previously cleared and
power.autosuspend_delay is negative
void pm_runtime_dont_use_autosuspend(struct device *dev);
`void pm_runtime_dont_use_autosuspend(struct device *dev);`
- clear the power.use_autosuspend flag, disabling autosuspend delays;
decrement the device's usage counter if the flag was previously set and
power.autosuspend_delay is negative; call pm_runtime_idle
void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);
`void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);`
- set the power.autosuspend_delay value to 'delay' (expressed in
milliseconds); if 'delay' is negative then runtime suspends are
prevented; if power.use_autosuspend is set, pm_runtime_get_sync may be
@ -493,7 +501,7 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
changed to or from a negative value; if power.use_autosuspend is clear,
pm_runtime_idle is called
unsigned long pm_runtime_autosuspend_expiration(struct device *dev);
`unsigned long pm_runtime_autosuspend_expiration(struct device *dev);`
- calculate the time when the current autosuspend delay period will expire,
based on power.last_busy and power.autosuspend_delay; if the delay time
is 1000 ms or larger then the expiration time is rounded up to the
@ -503,36 +511,37 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
It is safe to execute the following helper functions from interrupt context:
pm_request_idle()
pm_request_autosuspend()
pm_schedule_suspend()
pm_request_resume()
pm_runtime_get_noresume()
pm_runtime_get()
pm_runtime_put_noidle()
pm_runtime_put()
pm_runtime_put_autosuspend()
pm_runtime_enable()
pm_suspend_ignore_children()
pm_runtime_set_active()
pm_runtime_set_suspended()
pm_runtime_suspended()
pm_runtime_mark_last_busy()
pm_runtime_autosuspend_expiration()
- pm_request_idle()
- pm_request_autosuspend()
- pm_schedule_suspend()
- pm_request_resume()
- pm_runtime_get_noresume()
- pm_runtime_get()
- pm_runtime_put_noidle()
- pm_runtime_put()
- pm_runtime_put_autosuspend()
- pm_runtime_enable()
- pm_suspend_ignore_children()
- pm_runtime_set_active()
- pm_runtime_set_suspended()
- pm_runtime_suspended()
- pm_runtime_mark_last_busy()
- pm_runtime_autosuspend_expiration()
If pm_runtime_irq_safe() has been called for a device then the following helper
functions may also be used in interrupt context:
pm_runtime_idle()
pm_runtime_suspend()
pm_runtime_autosuspend()
pm_runtime_resume()
pm_runtime_get_sync()
pm_runtime_put_sync()
pm_runtime_put_sync_suspend()
pm_runtime_put_sync_autosuspend()
- pm_runtime_idle()
- pm_runtime_suspend()
- pm_runtime_autosuspend()
- pm_runtime_resume()
- pm_runtime_get_sync()
- pm_runtime_put_sync()
- pm_runtime_put_sync_suspend()
- pm_runtime_put_sync_autosuspend()
5. Runtime PM Initialization, Device Probing and Removal
========================================================
Initially, the runtime PM is disabled for all devices, which means that the
majority of the runtime PM helper functions described in Section 4 will return
@ -608,6 +617,7 @@ manage the device at run time, the driver may confuse it by using
pm_runtime_forbid() this way.
6. Runtime PM and System Sleep
==============================
Runtime PM and system sleep (i.e., system suspend and hibernation, also known
as suspend-to-RAM and suspend-to-disk) interact with each other in a couple of
@ -647,9 +657,9 @@ brought back to full power during resume, then its runtime PM status will have
to be updated to reflect the actual post-system sleep status. The way to do
this is:
pm_runtime_disable(dev);
pm_runtime_set_active(dev);
pm_runtime_enable(dev);
- pm_runtime_disable(dev);
- pm_runtime_set_active(dev);
- pm_runtime_enable(dev);
The PM core always increments the runtime usage counter before calling the
->suspend() callback and decrements it after calling the ->resume() callback.
@ -705,66 +715,66 @@ Subsystems may wish to conserve code space by using the set of generic power
management callbacks provided by the PM core, defined in
driver/base/power/generic_ops.c:
int pm_generic_runtime_suspend(struct device *dev);
`int pm_generic_runtime_suspend(struct device *dev);`
- invoke the ->runtime_suspend() callback provided by the driver of this
device and return its result, or return 0 if not defined
int pm_generic_runtime_resume(struct device *dev);
`int pm_generic_runtime_resume(struct device *dev);`
- invoke the ->runtime_resume() callback provided by the driver of this
device and return its result, or return 0 if not defined
int pm_generic_suspend(struct device *dev);
`int pm_generic_suspend(struct device *dev);`
- if the device has not been suspended at run time, invoke the ->suspend()
callback provided by its driver and return its result, or return 0 if not
defined
int pm_generic_suspend_noirq(struct device *dev);
`int pm_generic_suspend_noirq(struct device *dev);`
- if pm_runtime_suspended(dev) returns "false", invoke the ->suspend_noirq()
callback provided by the device's driver and return its result, or return
0 if not defined
int pm_generic_resume(struct device *dev);
`int pm_generic_resume(struct device *dev);`
- invoke the ->resume() callback provided by the driver of this device and,
if successful, change the device's runtime PM status to 'active'
int pm_generic_resume_noirq(struct device *dev);
`int pm_generic_resume_noirq(struct device *dev);`
- invoke the ->resume_noirq() callback provided by the driver of this device
int pm_generic_freeze(struct device *dev);
`int pm_generic_freeze(struct device *dev);`
- if the device has not been suspended at run time, invoke the ->freeze()
callback provided by its driver and return its result, or return 0 if not
defined
int pm_generic_freeze_noirq(struct device *dev);
`int pm_generic_freeze_noirq(struct device *dev);`
- if pm_runtime_suspended(dev) returns "false", invoke the ->freeze_noirq()
callback provided by the device's driver and return its result, or return
0 if not defined
int pm_generic_thaw(struct device *dev);
`int pm_generic_thaw(struct device *dev);`
- if the device has not been suspended at run time, invoke the ->thaw()
callback provided by its driver and return its result, or return 0 if not
defined
int pm_generic_thaw_noirq(struct device *dev);
`int pm_generic_thaw_noirq(struct device *dev);`
- if pm_runtime_suspended(dev) returns "false", invoke the ->thaw_noirq()
callback provided by the device's driver and return its result, or return
0 if not defined
int pm_generic_poweroff(struct device *dev);
`int pm_generic_poweroff(struct device *dev);`
- if the device has not been suspended at run time, invoke the ->poweroff()
callback provided by its driver and return its result, or return 0 if not
defined
int pm_generic_poweroff_noirq(struct device *dev);
`int pm_generic_poweroff_noirq(struct device *dev);`
- if pm_runtime_suspended(dev) returns "false", run the ->poweroff_noirq()
callback provided by the device's driver and return its result, or return
0 if not defined
int pm_generic_restore(struct device *dev);
`int pm_generic_restore(struct device *dev);`
- invoke the ->restore() callback provided by the driver of this device and,
if successful, change the device's runtime PM status to 'active'
int pm_generic_restore_noirq(struct device *dev);
`int pm_generic_restore_noirq(struct device *dev);`
- invoke the ->restore_noirq() callback provided by the device's driver
These functions are the defaults used by the PM core, if a subsystem doesn't
@ -781,6 +791,7 @@ UNIVERSAL_DEV_PM_OPS macro defined in include/linux/pm.h (possibly setting its
last argument to NULL).
8. "No-Callback" Devices
========================
Some "devices" are only logical sub-devices of their parent and cannot be
power-managed on their own. (The prototype example is a USB interface. Entire
@ -807,6 +818,7 @@ parent must take responsibility for telling the device's driver when the
parent's power state changes.
9. Autosuspend, or automatically-delayed suspends
=================================================
Changing a device's power state isn't free; it requires both time and energy.
A device should be put in a low-power state only when there's some reason to
@ -832,8 +844,8 @@ registration the length should be controlled by user space, using the
In order to use autosuspend, subsystems or drivers must call
pm_runtime_use_autosuspend() (preferably before registering the device), and
thereafter they should use the various *_autosuspend() helper functions instead
of the non-autosuspend counterparts:
thereafter they should use the various `*_autosuspend()` helper functions
instead of the non-autosuspend counterparts::
Instead of: pm_runtime_suspend use: pm_runtime_autosuspend;
Instead of: pm_schedule_suspend use: pm_request_autosuspend;
@ -858,7 +870,7 @@ The implementation is well suited for asynchronous use in interrupt contexts.
However such use inevitably involves races, because the PM core can't
synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
This synchronization must be handled by the driver, using its private lock.
Here is a schematic pseudo-code example:
Here is a schematic pseudo-code example::
foo_read_or_write(struct foo_priv *foo, void *data)
{

20
Documentation/power/s2ram.txt → Documentation/power/s2ram.rst
View File

@ -1,7 +1,9 @@
How to get s2ram working
~~~~~~~~~~~~~~~~~~~~~~~~
2006 Linus Torvalds
2006 Pavel Machek
========================
How to get s2ram working
========================
2006 Linus Torvalds
2006 Pavel Machek
1) Check suspend.sf.net, program s2ram there has long whitelist of
"known ok" machines, along with tricks to use on each one.
@ -12,8 +14,8 @@
3) You can use Linus' TRACE_RESUME infrastructure, described below.
Using TRACE_RESUME
~~~~~~~~~~~~~~~~~~
Using TRACE_RESUME
~~~~~~~~~~~~~~~~~~
I've been working at making the machines I have able to STR, and almost
always it's a driver that is buggy. Thank God for the suspend/resume
@ -27,7 +29,7 @@ machine that doesn't boot) is:
- enable PM_DEBUG, and PM_TRACE
- use a script like this:
- use a script like this::
#!/bin/sh
sync
@ -38,7 +40,7 @@ machine that doesn't boot) is:
- if it doesn't come back up (which is usually the problem), reboot by
holding the power button down, and look at the dmesg output for things
like
like::
Magic number: 4:156:725
hash matches drivers/base/power/resume.c:28
@ -52,7 +54,7 @@ machine that doesn't boot) is:
If no device matches the hash (or any matches appear to be false positives),
the culprit may be a device from a loadable kernel module that is not loaded
until after the hash is checked. You can check the hash against the current
devices again after more modules are loaded using sysfs:
devices again after more modules are loaded using sysfs::
cat /sys/power/pm_trace_dev_match

42
Documentation/power/suspend-and-cpuhotplug.txt → Documentation/power/suspend-and-cpuhotplug.rst
View File

@ -1,10 +1,15 @@
====================================================================
Interaction of Suspend code (S3) with the CPU hotplug infrastructure
====================================================================
(C) 2011 - 2014 Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
(C) 2011 - 2014 Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
I. How does the regular CPU hotplug code differ from how the Suspend-to-RAM
infrastructure uses it internally? And where do they share common code?
I. Differences between CPU hotplug and Suspend-to-RAM
======================================================
How does the regular CPU hotplug code differ from how the Suspend-to-RAM
infrastructure uses it internally? And where do they share common code?
Well, a picture is worth a thousand words... So ASCII art follows :-)
@ -16,13 +21,13 @@ of describing where they take different paths and where they share code.
What happens when regular CPU hotplug and Suspend-to-RAM race with each other
is not depicted here.]
On a high level, the suspend-resume cycle goes like this:
On a high level, the suspend-resume cycle goes like this::
|Freeze| -> |Disable nonboot| -> |Do suspend| -> |Enable nonboot| -> |Thaw |
|tasks | | cpus | | | | cpus | |tasks|
|Freeze| -> |Disable nonboot| -> |Do suspend| -> |Enable nonboot| -> |Thaw |
|tasks | | cpus | | | | cpus | |tasks|
More details follow:
More details follow::
Suspend call path
-----------------
@ -87,7 +92,9 @@ More details follow:
Resuming back is likewise, with the counterparts being (in the order of
execution during resume):
* enable_nonboot_cpus() which involves:
* enable_nonboot_cpus() which involves::
| Acquire cpu_add_remove_lock
| Decrease cpu_hotplug_disabled, thereby enabling regular cpu hotplug
| Call _cpu_up() [for all those cpus in the frozen_cpus mask, in a loop]
@ -103,6 +110,8 @@ It is to be noted here that the system_transition_mutex lock is acquired at the
beginning, when we are just starting out to suspend, and then released only
after the entire cycle is complete (i.e., suspend + resume).
::
Regular CPU hotplug call path
@ -152,16 +161,16 @@ with the 'tasks_frozen' argument set to 1.
Important files and functions/entry points:
------------------------------------------
-------------------------------------------
kernel/power/process.c : freeze_processes(), thaw_processes()
kernel/power/suspend.c : suspend_prepare(), suspend_enter(), suspend_finish()
kernel/cpu.c: cpu_[up|down](), _cpu_[up|down](), [disable|enable]_nonboot_cpus()
- kernel/power/process.c : freeze_processes(), thaw_processes()
- kernel/power/suspend.c : suspend_prepare(), suspend_enter(), suspend_finish()
- kernel/cpu.c: cpu_[up|down](), _cpu_[up|down](), [disable|enable]_nonboot_cpus()
II. What are the issues involved in CPU hotplug?
-------------------------------------------
------------------------------------------------
There are some interesting situations involving CPU hotplug and microcode
update on the CPUs, as discussed below:
@ -243,8 +252,11 @@ d. Handling microcode update during suspend/hibernate:
cycles).
III. Are there any known problems when regular CPU hotplug and suspend race
with each other?
III. Known problems
===================
Are there any known problems when regular CPU hotplug and suspend race
with each other?
Yes, they are listed below:

2
Documentation/power/suspend-and-interrupts.txt → Documentation/power/suspend-and-interrupts.rst
View File

@ -1,4 +1,6 @@
====================================
System Suspend and Device Interrupts
====================================
Copyright (C) 2014 Intel Corp.
Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

17
Documentation/power/swsusp-and-swap-files.txt → Documentation/power/swsusp-and-swap-files.rst
View File

@ -1,4 +1,7 @@
===============================================
Using swap files with software suspend (swsusp)
===============================================
(C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
The Linux kernel handles swap files almost in the same way as it handles swap
@ -21,20 +24,20 @@ units.
In order to use a swap file with swsusp, you need to:
1) Create the swap file and make it active, eg.
1) Create the swap file and make it active, eg.::
# dd if=/dev/zero of=<swap_file_path> bs=1024 count=<swap_file_size_in_k>
# mkswap <swap_file_path>
# swapon <swap_file_path>
# dd if=/dev/zero of=<swap_file_path> bs=1024 count=<swap_file_size_in_k>
# mkswap <swap_file_path>
# swapon <swap_file_path>
2) Use an application that will bmap the swap file with the help of the
FIBMAP ioctl and determine the location of the file's swap header, as the
offset, in <PAGE_SIZE> units, from the beginning of the partition which
holds the swap file.
3) Add the following parameters to the kernel command line:
3) Add the following parameters to the kernel command line::
resume=<swap_file_partition> resume_offset=<swap_file_offset>
resume=<swap_file_partition> resume_offset=<swap_file_offset>
where <swap_file_partition> is the partition on which the swap file is located
and <swap_file_offset> is the offset of the swap header determined by the
@ -46,7 +49,7 @@ OR
Use a userland suspend application that will set the partition and offset
with the help of the SNAPSHOT_SET_SWAP_AREA ioctl described in
Documentation/power/userland-swsusp.txt (this is the only method to suspend
Documentation/power/userland-swsusp.rst (this is the only method to suspend
to a swap file allowing the resume to be initiated from an initrd or initramfs
image).

120
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View File

@ -1,13 +1,15 @@
=======================================
How to use dm-crypt and swsusp together
=======================================
Author: Andreas Steinmetz <ast@domdv.de>
How to use dm-crypt and swsusp together:
========================================
Some prerequisites:
You know how dm-crypt works. If not, visit the following web page:
http://www.saout.de/misc/dm-crypt/
You have read Documentation/power/swsusp.txt and understand it.
You have read Documentation/power/swsusp.rst and understand it.
You did read Documentation/admin-guide/initrd.rst and know how an initrd works.
You know how to create or how to modify an initrd.
@ -29,23 +31,23 @@ a way that the swap device you suspend to/resume from has
always the same major/minor within the initrd as well as
within your running system. The easiest way to achieve this is
to always set up this swap device first with dmsetup, so that
it will always look like the following:
it will always look like the following::
brw------- 1 root root 254, 0 Jul 28 13:37 /dev/mapper/swap0
brw------- 1 root root 254, 0 Jul 28 13:37 /dev/mapper/swap0
Now set up your kernel to use /dev/mapper/swap0 as the default
resume partition, so your kernel .config contains:
resume partition, so your kernel .config contains::
CONFIG_PM_STD_PARTITION="/dev/mapper/swap0"
CONFIG_PM_STD_PARTITION="/dev/mapper/swap0"
Prepare your boot loader to use the initrd you will create or
modify. For lilo the simplest setup looks like the following
lines:
lines::
image=/boot/vmlinuz
initrd=/boot/initrd.gz
label=linux
append="root=/dev/ram0 init=/linuxrc rw"
image=/boot/vmlinuz
initrd=/boot/initrd.gz
label=linux
append="root=/dev/ram0 init=/linuxrc rw"
Finally you need to create or modify your initrd. Lets assume
you create an initrd that reads the required dm-crypt setup
@ -53,66 +55,66 @@ from a pcmcia flash disk card. The card is formatted with an ext2
fs which resides on /dev/hde1 when the card is inserted. The
card contains at least the encrypted swap setup in a file
named "swapkey". /etc/fstab of your initrd contains something
like the following:
like the following::
/dev/hda1 /mnt ext3 ro 0 0
none /proc proc defaults,noatime,nodiratime 0 0
none /sys sysfs defaults,noatime,nodiratime 0 0
/dev/hda1 /mnt ext3 ro 0 0
none /proc proc defaults,noatime,nodiratime 0 0
none /sys sysfs defaults,noatime,nodiratime 0 0
/dev/hda1 contains an unencrypted mini system that sets up all
of your crypto devices, again by reading the setup from the
pcmcia flash disk. What follows now is a /linuxrc for your
initrd that allows you to resume from encrypted swap and that
continues boot with your mini system on /dev/hda1 if resume
does not happen:
does not happen::
#!/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
mount /proc
mount /sys
mapped=0
noresume=`grep -c noresume /proc/cmdline`
if [ "$*" != "" ]
then
noresume=1
fi
dmesg -n 1
/sbin/cardmgr -q
for i in 1 2 3 4 5 6 7 8 9 0
do
if [ -f /proc/ide/hde/media ]
#!/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
mount /proc
mount /sys
mapped=0
noresume=`grep -c noresume /proc/cmdline`
if [ "$*" != "" ]
then
usleep 500000
mount -t ext2 -o ro /dev/hde1 /mnt
if [ -f /mnt/swapkey ]
noresume=1
fi
dmesg -n 1
/sbin/cardmgr -q
for i in 1 2 3 4 5 6 7 8 9 0
do
if [ -f /proc/ide/hde/media ]
then
dmsetup create swap0 /mnt/swapkey > /dev/null 2>&1 && mapped=1
usleep 500000
mount -t ext2 -o ro /dev/hde1 /mnt
if [ -f /mnt/swapkey ]
then
dmsetup create swap0 /mnt/swapkey > /dev/null 2>&1 && mapped=1
fi
umount /mnt
break
fi
umount /mnt
break
fi
usleep 500000
done
killproc /sbin/cardmgr
dmesg -n 6
if [ $mapped = 1 ]
then
if [ $noresume != 0 ]
usleep 500000
done
killproc /sbin/cardmgr
dmesg -n 6
if [ $mapped = 1 ]
then
mkswap /dev/mapper/swap0 > /dev/null 2>&1
if [ $noresume != 0 ]
then
mkswap /dev/mapper/swap0 > /dev/null 2>&1
fi
echo 254:0 > /sys/power/resume
dmsetup remove swap0
fi
echo 254:0 > /sys/power/resume
dmsetup remove swap0
fi
umount /sys
mount /mnt
umount /proc
cd /mnt
pivot_root . mnt
mount /proc
umount -l /mnt
umount /proc
exec chroot . /sbin/init $* < dev/console > dev/console 2>&1
umount /sys
mount /mnt
umount /proc
cd /mnt
pivot_root . mnt
mount /proc
umount -l /mnt
umount /proc
exec chroot . /sbin/init $* < dev/console > dev/console 2>&1
Please don't mind the weird loop above, busybox's msh doesn't know
the let statement. Now, what is happening in the script?

501
Documentation/power/swsusp.rst Normal file
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@ -0,0 +1,501 @@
============
Swap suspend
============
Some warnings, first.
.. warning::
**BIG FAT WARNING**
If you touch anything on disk between suspend and resume...
...kiss your data goodbye.
If you do resume from initrd after your filesystems are mounted...
...bye bye root partition.
[this is actually same case as above]
If you have unsupported ( ) devices using DMA, you may have some
problems. If your disk driver does not support suspend... (IDE does),
it may cause some problems, too. If you change kernel command line
between suspend and resume, it may do something wrong. If you change
your hardware while system is suspended... well, it was not good idea;
but it will probably only crash.
( ) suspend/resume support is needed to make it safe.
If you have any filesystems on USB devices mounted before software suspend,
they won't be accessible after resume and you may lose data, as though
you have unplugged the USB devices with mounted filesystems on them;
see the FAQ below for details. (This is not true for more traditional
power states like "standby", which normally don't turn USB off.)
Swap partition:
You need to append resume=/dev/your_swap_partition to kernel command
line or specify it using /sys/power/resume.
Swap file:
If using a swapfile you can also specify a resume offset using
resume_offset=<number> on the kernel command line or specify it
in /sys/power/resume_offset.
After preparing then you suspend by::
echo shutdown > /sys/power/disk; echo disk > /sys/power/state
- If you feel ACPI works pretty well on your system, you might try::
echo platform > /sys/power/disk; echo disk > /sys/power/state
- If you would like to write hibernation image to swap and then suspend
to RAM (provided your platform supports it), you can try::
echo suspend > /sys/power/disk; echo disk > /sys/power/state
- If you have SATA disks, you'll need recent kernels with SATA suspend
support. For suspend and resume to work, make sure your disk drivers
are built into kernel -- not modules. [There's way to make
suspend/resume with modular disk drivers, see FAQ, but you probably
should not do that.]
If you want to limit the suspend image size to N bytes, do::
echo N > /sys/power/image_size
before suspend (it is limited to around 2/5 of available RAM by default).
- The resume process checks for the presence of the resume device,
if found, it then checks the contents for the hibernation image signature.
If both are found, it resumes the hibernation image.
- The resume process may be triggered in two ways:
1) During lateinit: If resume=/dev/your_swap_partition is specified on
the kernel command line, lateinit runs the resume process. If the
resume device has not been probed yet, the resume process fails and
bootup continues.
2) Manually from an initrd or initramfs: May be run from
the init script by using the /sys/power/resume file. It is vital
that this be done prior to remounting any filesystems (even as
read-only) otherwise data may be corrupted.
Article about goals and implementation of Software Suspend for Linux
====================================================================
Author: Gábor Kuti
Last revised: 2003-10-20 by Pavel Machek
Idea and goals to achieve
-------------------------
Nowadays it is common in several laptops that they have a suspend button. It
saves the state of the machine to a filesystem or to a partition and switches
to standby mode. Later resuming the machine the saved state is loaded back to
ram and the machine can continue its work. It has two real benefits. First we
save ourselves the time machine goes down and later boots up, energy costs
are real high when running from batteries. The other gain is that we don't have
to interrupt our programs so processes that are calculating something for a long
time shouldn't need to be written interruptible.
swsusp saves the state of the machine into active swaps and then reboots or
powerdowns. You must explicitly specify the swap partition to resume from with
`resume=` kernel option. If signature is found it loads and restores saved
state. If the option `noresume` is specified as a boot parameter, it skips
the resuming. If the option `hibernate=nocompress` is specified as a boot
parameter, it saves hibernation image without compression.
In the meantime while the system is suspended you should not add/remove any
of the hardware, write to the filesystems, etc.
Sleep states summary
====================
There are three different interfaces you can use, /proc/acpi should
work like this:
In a really perfect world::
echo 1 > /proc/acpi/sleep # for standby
echo 2 > /proc/acpi/sleep # for suspend to ram
echo 3 > /proc/acpi/sleep # for suspend to ram, but with more power conservative
echo 4 > /proc/acpi/sleep # for suspend to disk
echo 5 > /proc/acpi/sleep # for shutdown unfriendly the system
and perhaps::
echo 4b > /proc/acpi/sleep # for suspend to disk via s4bios
Frequently Asked Questions
==========================
Q:
well, suspending a server is IMHO a really stupid thing,
but... (Diego Zuccato):
A:
You bought new UPS for your server. How do you install it without
bringing machine down? Suspend to disk, rearrange power cables,
resume.
You have your server on UPS. Power died, and UPS is indicating 30
seconds to failure. What do you do? Suspend to disk.
Q:
Maybe I'm missing something, but why don't the regular I/O paths work?
A:
We do use the regular I/O paths. However we cannot restore the data
to its original location as we load it. That would create an
inconsistent kernel state which would certainly result in an oops.
Instead, we load the image into unused memory and then atomically copy
it back to it original location. This implies, of course, a maximum
image size of half the amount of memory.
There are two solutions to this:
* require half of memory to be free during suspend. That way you can
read "new" data onto free spots, then cli and copy
* assume we had special "polling" ide driver that only uses memory
between 0-640KB. That way, I'd have to make sure that 0-640KB is free
during suspending, but otherwise it would work...
suspend2 shares this fundamental limitation, but does not include user
data and disk caches into "used memory" by saving them in
advance. That means that the limitation goes away in practice.
Q:
Does linux support ACPI S4?
A:
Yes. That's what echo platform > /sys/power/disk does.
Q:
What is 'suspend2'?
A:
suspend2 is 'Software Suspend 2', a forked implementation of
suspend-to-disk which is available as separate patches for 2.4 and 2.6
kernels from swsusp.sourceforge.net. It includes support for SMP, 4GB
highmem and preemption. It also has a extensible architecture that
allows for arbitrary transformations on the image (compression,
encryption) and arbitrary backends for writing the image (eg to swap
or an NFS share[Work In Progress]). Questions regarding suspend2
should be sent to the mailing list available through the suspend2
website, and not to the Linux Kernel Mailing List. We are working
toward merging suspend2 into the mainline kernel.
Q:
What is the freezing of tasks and why are we using it?
A:
The freezing of tasks is a mechanism by which user space processes and some
kernel threads are controlled during hibernation or system-wide suspend (on some
architectures). See freezing-of-tasks.txt for details.
Q:
What is the difference between "platform" and "shutdown"?
A:
shutdown:
save state in linux, then tell bios to powerdown
platform:
save state in linux, then tell bios to powerdown and blink
"suspended led"
"platform" is actually right thing to do where supported, but
"shutdown" is most reliable (except on ACPI systems).
Q:
I do not understand why you have such strong objections to idea of
selective suspend.
A:
Do selective suspend during runtime power management, that's okay. But
it's useless for suspend-to-disk. (And I do not see how you could use
it for suspend-to-ram, I hope you do not want that).
Lets see, so you suggest to
* SUSPEND all but swap device and parents
* Snapshot
* Write image to disk
* SUSPEND swap device and parents
* Powerdown
Oh no, that does not work, if swap device or its parents uses DMA,
you've corrupted data. You'd have to do
* SUSPEND all but swap device and parents
* FREEZE swap device and parents
* Snapshot
* UNFREEZE swap device and parents
* Write
* SUSPEND swap device and parents
Which means that you still need that FREEZE state, and you get more
complicated code. (And I have not yet introduce details like system
devices).
Q:
There don't seem to be any generally useful behavioral
distinctions between SUSPEND and FREEZE.
A:
Doing SUSPEND when you are asked to do FREEZE is always correct,
but it may be unnecessarily slow. If you want your driver to stay simple,
slowness may not matter to you. It can always be fixed later.
For devices like disk it does matter, you do not want to spindown for
FREEZE.
Q:
After resuming, system is paging heavily, leading to very bad interactivity.
A:
Try running::
cat /proc/[0-9]*/maps | grep / | sed 's:.* /:/:' | sort -u | while read file
do
test -f "$file" && cat "$file" > /dev/null
done
after resume. swapoff -a; swapon -a may also be useful.
Q:
What happens to devices during swsusp? They seem to be resumed
during system suspend?
A:
That's correct. We need to resume them if we want to write image to
disk. Whole sequence goes like
**Suspend part**
running system, user asks for suspend-to-disk
user processes are stopped
suspend(PMSG_FREEZE): devices are frozen so that they don't interfere
with state snapshot
state snapshot: copy of whole used memory is taken with interrupts disabled
resume(): devices are woken up so that we can write image to swap
write image to swap
suspend(PMSG_SUSPEND): suspend devices so that we can power off
turn the power off
**Resume part**
(is actually pretty similar)
running system, user asks for suspend-to-disk
user processes are stopped (in common case there are none,
but with resume-from-initrd, no one knows)
read image from disk
suspend(PMSG_FREEZE): devices are frozen so that they don't interfere
with image restoration
image restoration: rewrite memory with image
resume(): devices are woken up so that system can continue
thaw all user processes
Q:
What is this 'Encrypt suspend image' for?
A:
First of all: it is not a replacement for dm-crypt encrypted swap.
It cannot protect your computer while it is suspended. Instead it does
protect from leaking sensitive data after resume from suspend.
Think of the following: you suspend while an application is running
that keeps sensitive data in memory. The application itself prevents
the data from being swapped out. Suspend, however, must write these
data to swap to be able to resume later on. Without suspend encryption
your sensitive data are then stored in plaintext on disk. This means
that after resume your sensitive data are accessible to all
applications having direct access to the swap device which was used
for suspend. If you don't need swap after resume these data can remain
on disk virtually forever. Thus it can happen that your system gets
broken in weeks later and sensitive data which you thought were
encrypted and protected are retrieved and stolen from the swap device.
To prevent this situation you should use 'Encrypt suspend image'.
During suspend a temporary key is created and this key is used to
encrypt the data written to disk. When, during resume, the data was
read back into memory the temporary key is destroyed which simply
means that all data written to disk during suspend are then
inaccessible so they can't be stolen later on. The only thing that
you must then take care of is that you call 'mkswap' for the swap
partition used for suspend as early as possible during regular
boot. This asserts that any temporary key from an oopsed suspend or
from a failed or aborted resume is erased from the swap device.
As a rule of thumb use encrypted swap to protect your data while your
system is shut down or suspended. Additionally use the encrypted
suspend image to prevent sensitive data from being stolen after
resume.
Q:
Can I suspend to a swap file?
A:
Generally, yes, you can. However, it requires you to use the "resume=" and
"resume_offset=" kernel command line parameters, so the resume from a swap file
cannot be initiated from an initrd or initramfs image. See
swsusp-and-swap-files.txt for details.
Q:
Is there a maximum system RAM size that is supported by swsusp?
A:
It should work okay with highmem.
Q:
Does swsusp (to disk) use only one swap partition or can it use
multiple swap partitions (aggregate them into one logical space)?
A:
Only one swap partition, sorry.
Q:
If my application(s) causes lots of memory & swap space to be used
(over half of the total system RAM), is it correct that it is likely
to be useless to try to suspend to disk while that app is running?
A:
No, it should work okay, as long as your app does not mlock()
it. Just prepare big enough swap partition.
Q:
What information is useful for debugging suspend-to-disk problems?
A:
Well, last messages on the screen are always useful. If something
is broken, it is usually some kernel driver, therefore trying with as
little as possible modules loaded helps a lot. I also prefer people to
suspend from console, preferably without X running. Booting with
init=/bin/bash, then swapon and starting suspend sequence manually
usually does the trick. Then it is good idea to try with latest
vanilla kernel.
Q:
How can distributions ship a swsusp-supporting kernel with modular
disk drivers (especially SATA)?
A:
Well, it can be done, load the drivers, then do echo into
/sys/power/resume file from initrd. Be sure not to mount
anything, not even read-only mount, or you are going to lose your
data.
Q:
How do I make suspend more verbose?
A:
If you want to see any non-error kernel messages on the virtual
terminal the kernel switches to during suspend, you have to set the
kernel console loglevel to at least 4 (KERN_WARNING), for example by
doing::
# save the old loglevel
read LOGLEVEL DUMMY < /proc/sys/kernel/printk
# set the loglevel so we see the progress bar.
# if the level is higher than needed, we leave it alone.
if [ $LOGLEVEL -lt 5 ]; then
echo 5 > /proc/sys/kernel/printk
fi
IMG_SZ=0
read IMG_SZ < /sys/power/image_size
echo -n disk > /sys/power/state
RET=$?
#
# the logic here is:
# if image_size > 0 (without kernel support, IMG_SZ will be zero),
# then try again with image_size set to zero.
if [ $RET -ne 0 -a $IMG_SZ -ne 0 ]; then # try again with minimal image size
echo 0 > /sys/power/image_size
echo -n disk > /sys/power/state
RET=$?
fi
# restore previous loglevel
echo $LOGLEVEL > /proc/sys/kernel/printk
exit $RET
Q:
Is this true that if I have a mounted filesystem on a USB device and
I suspend to disk, I can lose data unless the filesystem has been mounted
with "sync"?
A:
That's right ... if you disconnect that device, you may lose data.
In fact, even with "-o sync" you can lose data if your programs have
information in buffers they haven't written out to a disk you disconnect,
or if you disconnect before the device finished saving data you wrote.
Software suspend normally powers down USB controllers, which is equivalent
to disconnecting all USB devices attached to your system.
Your system might well support low-power modes for its USB controllers
while the system is asleep, maintaining the connection, using true sleep
modes like "suspend-to-RAM" or "standby". (Don't write "disk" to the
/sys/power/state file; write "standby" or "mem".) We've not seen any
hardware that can use these modes through software suspend, although in
theory some systems might support "platform" modes that won't break the
USB connections.
Remember that it's always a bad idea to unplug a disk drive containing a
mounted filesystem. That's true even when your system is asleep! The
safest thing is to unmount all filesystems on removable media (such USB,
Firewire, CompactFlash, MMC, external SATA, or even IDE hotplug bays)
before suspending; then remount them after resuming.
There is a work-around for this problem. For more information, see
Documentation/driver-api/usb/persist.rst.
Q:
Can I suspend-to-disk using a swap partition under LVM?
A:
Yes and No. You can suspend successfully, but the kernel will not be able
to resume on its own. You need an initramfs that can recognize the resume
situation, activate the logical volume containing the swap volume (but not
touch any filesystems!), and eventually call::
echo -n "$major:$minor" > /sys/power/resume
where $major and $minor are the respective major and minor device numbers of
the swap volume.
uswsusp works with LVM, too. See http://suspend.sourceforge.net/
Q:
I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were
compiled with the similar configuration files. Anyway I found that
suspend to disk (and resume) is much slower on 2.6.16 compared to
2.6.15. Any idea for why that might happen or how can I speed it up?
A:
This is because the size of the suspend image is now greater than
for 2.6.15 (by saving more data we can get more responsive system
after resume).
There's the /sys/power/image_size knob that controls the size of the
image. If you set it to 0 (eg. by echo 0 > /sys/power/image_size as
root), the 2.6.15 behavior should be restored. If it is still too
slow, take a look at suspend.sf.net -- userland suspend is faster and
supports LZF compression to speed it up further.

446
Documentation/power/swsusp.txt
View File

@ -1,446 +0,0 @@
Some warnings, first.
* BIG FAT WARNING *********************************************************
*
* If you touch anything on disk between suspend and resume...
* ...kiss your data goodbye.
*
* If you do resume from initrd after your filesystems are mounted...
* ...bye bye root partition.
* [this is actually same case as above]
*
* If you have unsupported (*) devices using DMA, you may have some
* problems. If your disk driver does not support suspend... (IDE does),
* it may cause some problems, too. If you change kernel command line
* between suspend and resume, it may do something wrong. If you change
* your hardware while system is suspended... well, it was not good idea;
* but it will probably only crash.
*
* (*) suspend/resume support is needed to make it safe.
*
* If you have any filesystems on USB devices mounted before software suspend,
* they won't be accessible after resume and you may lose data, as though
* you have unplugged the USB devices with mounted filesystems on them;
* see the FAQ below for details. (This is not true for more traditional
* power states like "standby", which normally don't turn USB off.)
Swap partition:
You need to append resume=/dev/your_swap_partition to kernel command
line or specify it using /sys/power/resume.
Swap file:
If using a swapfile you can also specify a resume offset using
resume_offset=<number> on the kernel command line or specify it
in /sys/power/resume_offset.
After preparing then you suspend by
echo shutdown > /sys/power/disk; echo disk > /sys/power/state
. If you feel ACPI works pretty well on your system, you might try
echo platform > /sys/power/disk; echo disk > /sys/power/state
. If you would like to write hibernation image to swap and then suspend
to RAM (provided your platform supports it), you can try
echo suspend > /sys/power/disk; echo disk > /sys/power/state
. If you have SATA disks, you'll need recent kernels with SATA suspend
support. For suspend and resume to work, make sure your disk drivers
are built into kernel -- not modules. [There's way to make
suspend/resume with modular disk drivers, see FAQ, but you probably
should not do that.]
If you want to limit the suspend image size to N bytes, do
echo N > /sys/power/image_size
before suspend (it is limited to around 2/5 of available RAM by default).
. The resume process checks for the presence of the resume device,
if found, it then checks the contents for the hibernation image signature.
If both are found, it resumes the hibernation image.
. The resume process may be triggered in two ways:
1) During lateinit: If resume=/dev/your_swap_partition is specified on
the kernel command line, lateinit runs the resume process. If the
resume device has not been probed yet, the resume process fails and
bootup continues.
2) Manually from an initrd or initramfs: May be run from
the init script by using the /sys/power/resume file. It is vital
that this be done prior to remounting any filesystems (even as
read-only) otherwise data may be corrupted.
Article about goals and implementation of Software Suspend for Linux
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Author: Gábor Kuti
Last revised: 2003-10-20 by Pavel Machek
Idea and goals to achieve
Nowadays it is common in several laptops that they have a suspend button. It
saves the state of the machine to a filesystem or to a partition and switches
to standby mode. Later resuming the machine the saved state is loaded back to
ram and the machine can continue its work. It has two real benefits. First we
save ourselves the time machine goes down and later boots up, energy costs
are real high when running from batteries. The other gain is that we don't have to
interrupt our programs so processes that are calculating something for a long
time shouldn't need to be written interruptible.
swsusp saves the state of the machine into active swaps and then reboots or
powerdowns. You must explicitly specify the swap partition to resume from with
``resume='' kernel option. If signature is found it loads and restores saved
state. If the option ``noresume'' is specified as a boot parameter, it skips
the resuming. If the option ``hibernate=nocompress'' is specified as a boot
parameter, it saves hibernation image without compression.
In the meantime while the system is suspended you should not add/remove any
of the hardware, write to the filesystems, etc.
Sleep states summary
====================
There are three different interfaces you can use, /proc/acpi should
work like this:
In a really perfect world:
echo 1 > /proc/acpi/sleep # for standby
echo 2 > /proc/acpi/sleep # for suspend to ram
echo 3 > /proc/acpi/sleep # for suspend to ram, but with more power conservative
echo 4 > /proc/acpi/sleep # for suspend to disk
echo 5 > /proc/acpi/sleep # for shutdown unfriendly the system
and perhaps
echo 4b > /proc/acpi/sleep # for suspend to disk via s4bios
Frequently Asked Questions
==========================
Q: well, suspending a server is IMHO a really stupid thing,
but... (Diego Zuccato):
A: You bought new UPS for your server. How do you install it without
bringing machine down? Suspend to disk, rearrange power cables,
resume.
You have your server on UPS. Power died, and UPS is indicating 30
seconds to failure. What do you do? Suspend to disk.
Q: Maybe I'm missing something, but why don't the regular I/O paths work?
A: We do use the regular I/O paths. However we cannot restore the data
to its original location as we load it. That would create an
inconsistent kernel state which would certainly result in an oops.
Instead, we load the image into unused memory and then atomically copy
it back to it original location. This implies, of course, a maximum
image size of half the amount of memory.
There are two solutions to this:
* require half of memory to be free during suspend. That way you can
read "new" data onto free spots, then cli and copy
* assume we had special "polling" ide driver that only uses memory
between 0-640KB. That way, I'd have to make sure that 0-640KB is free
during suspending, but otherwise it would work...
suspend2 shares this fundamental limitation, but does not include user
data and disk caches into "used memory" by saving them in
advance. That means that the limitation goes away in practice.
Q: Does linux support ACPI S4?
A: Yes. That's what echo platform > /sys/power/disk does.
Q: What is 'suspend2'?
A: suspend2 is 'Software Suspend 2', a forked implementation of
suspend-to-disk which is available as separate patches for 2.4 and 2.6
kernels from swsusp.sourceforge.net. It includes support for SMP, 4GB
highmem and preemption. It also has a extensible architecture that
allows for arbitrary transformations on the image (compression,
encryption) and arbitrary backends for writing the image (eg to swap
or an NFS share[Work In Progress]). Questions regarding suspend2
should be sent to the mailing list available through the suspend2
website, and not to the Linux Kernel Mailing List. We are working
toward merging suspend2 into the mainline kernel.
Q: What is the freezing of tasks and why are we using it?
A: The freezing of tasks is a mechanism by which user space processes and some
kernel threads are controlled during hibernation or system-wide suspend (on some
architectures). See freezing-of-tasks.txt for details.
Q: What is the difference between "platform" and "shutdown"?
A:
shutdown: save state in linux, then tell bios to powerdown
platform: save state in linux, then tell bios to powerdown and blink
"suspended led"
"platform" is actually right thing to do where supported, but
"shutdown" is most reliable (except on ACPI systems).
Q: I do not understand why you have such strong objections to idea of
selective suspend.
A: Do selective suspend during runtime power management, that's okay. But
it's useless for suspend-to-disk. (And I do not see how you could use
it for suspend-to-ram, I hope you do not want that).
Lets see, so you suggest to
* SUSPEND all but swap device and parents
* Snapshot
* Write image to disk
* SUSPEND swap device and parents
* Powerdown
Oh no, that does not work, if swap device or its parents uses DMA,
you've corrupted data. You'd have to do
* SUSPEND all but swap device and parents
* FREEZE swap device and parents
* Snapshot
* UNFREEZE swap device and parents
* Write
* SUSPEND swap device and parents
Which means that you still need that FREEZE state, and you get more
complicated code. (And I have not yet introduce details like system
devices).
Q: There don't seem to be any generally useful behavioral
distinctions between SUSPEND and FREEZE.
A: Doing SUSPEND when you are asked to do FREEZE is always correct,
but it may be unnecessarily slow. If you want your driver to stay simple,
slowness may not matter to you. It can always be fixed later.
For devices like disk it does matter, you do not want to spindown for
FREEZE.
Q: After resuming, system is paging heavily, leading to very bad interactivity.
A: Try running
cat /proc/[0-9]*/maps | grep / | sed 's:.* /:/:' | sort -u | while read file
do
test -f "$file" && cat "$file" > /dev/null
done
after resume. swapoff -a; swapon -a may also be useful.
Q: What happens to devices during swsusp? They seem to be resumed
during system suspend?
A: That's correct. We need to resume them if we want to write image to
disk. Whole sequence goes like
Suspend part
~~~~~~~~~~~~
running system, user asks for suspend-to-disk
user processes are stopped
suspend(PMSG_FREEZE): devices are frozen so that they don't interfere
with state snapshot
state snapshot: copy of whole used memory is taken with interrupts disabled
resume(): devices are woken up so that we can write image to swap
write image to swap
suspend(PMSG_SUSPEND): suspend devices so that we can power off
turn the power off
Resume part
~~~~~~~~~~~
(is actually pretty similar)
running system, user asks for suspend-to-disk
user processes are stopped (in common case there are none, but with resume-from-initrd, no one knows)
read image from disk
suspend(PMSG_FREEZE): devices are frozen so that they don't interfere
with image restoration
image restoration: rewrite memory with image
resume(): devices are woken up so that system can continue
thaw all user processes
Q: What is this 'Encrypt suspend image' for?
A: First of all: it is not a replacement for dm-crypt encrypted swap.
It cannot protect your computer while it is suspended. Instead it does
protect from leaking sensitive data after resume from suspend.
Think of the following: you suspend while an application is running
that keeps sensitive data in memory. The application itself prevents
the data from being swapped out. Suspend, however, must write these
data to swap to be able to resume later on. Without suspend encryption
your sensitive data are then stored in plaintext on disk. This means
that after resume your sensitive data are accessible to all
applications having direct access to the swap device which was used
for suspend. If you don't need swap after resume these data can remain
on disk virtually forever. Thus it can happen that your system gets
broken in weeks later and sensitive data which you thought were
encrypted and protected are retrieved and stolen from the swap device.
To prevent this situation you should use 'Encrypt suspend image'.
During suspend a temporary key is created and this key is used to
encrypt the data written to disk. When, during resume, the data was
read back into memory the temporary key is destroyed which simply
means that all data written to disk during suspend are then
inaccessible so they can't be stolen later on. The only thing that
you must then take care of is that you call 'mkswap' for the swap
partition used for suspend as early as possible during regular
boot. This asserts that any temporary key from an oopsed suspend or
from a failed or aborted resume is erased from the swap device.
As a rule of thumb use encrypted swap to protect your data while your
system is shut down or suspended. Additionally use the encrypted
suspend image to prevent sensitive data from being stolen after
resume.
Q: Can I suspend to a swap file?
A: Generally, yes, you can. However, it requires you to use the "resume=" and
"resume_offset=" kernel command line parameters, so the resume from a swap file
cannot be initiated from an initrd or initramfs image. See
swsusp-and-swap-files.txt for details.
Q: Is there a maximum system RAM size that is supported by swsusp?
A: It should work okay with highmem.
Q: Does swsusp (to disk) use only one swap partition or can it use
multiple swap partitions (aggregate them into one logical space)?
A: Only one swap partition, sorry.
Q: If my application(s) causes lots of memory & swap space to be used
(over half of the total system RAM), is it correct that it is likely
to be useless to try to suspend to disk while that app is running?
A: No, it should work okay, as long as your app does not mlock()
it. Just prepare big enough swap partition.
Q: What information is useful for debugging suspend-to-disk problems?
A: Well, last messages on the screen are always useful. If something
is broken, it is usually some kernel driver, therefore trying with as
little as possible modules loaded helps a lot. I also prefer people to
suspend from console, preferably without X running. Booting with
init=/bin/bash, then swapon and starting suspend sequence manually
usually does the trick. Then it is good idea to try with latest
vanilla kernel.
Q: How can distributions ship a swsusp-supporting kernel with modular
disk drivers (especially SATA)?
A: Well, it can be done, load the drivers, then do echo into
/sys/power/resume file from initrd. Be sure not to mount
anything, not even read-only mount, or you are going to lose your
data.
Q: How do I make suspend more verbose?
A: If you want to see any non-error kernel messages on the virtual
terminal the kernel switches to during suspend, you have to set the
kernel console loglevel to at least 4 (KERN_WARNING), for example by
doing
# save the old loglevel
read LOGLEVEL DUMMY < /proc/sys/kernel/printk
# set the loglevel so we see the progress bar.
# if the level is higher than needed, we leave it alone.
if [ $LOGLEVEL -lt 5 ]; then
echo 5 > /proc/sys/kernel/printk
fi
IMG_SZ=0
read IMG_SZ < /sys/power/image_size
echo -n disk > /sys/power/state
RET=$?
#
# the logic here is:
# if image_size > 0 (without kernel support, IMG_SZ will be zero),
# then try again with image_size set to zero.
if [ $RET -ne 0 -a $IMG_SZ -ne 0 ]; then # try again with minimal image size
echo 0 > /sys/power/image_size
echo -n disk > /sys/power/state
RET=$?
fi
# restore previous loglevel
echo $LOGLEVEL > /proc/sys/kernel/printk
exit $RET
Q: Is this true that if I have a mounted filesystem on a USB device and
I suspend to disk, I can lose data unless the filesystem has been mounted
with "sync"?
A: That's right ... if you disconnect that device, you may lose data.
In fact, even with "-o sync" you can lose data if your programs have
information in buffers they haven't written out to a disk you disconnect,
or if you disconnect before the device finished saving data you wrote.
Software suspend normally powers down USB controllers, which is equivalent
to disconnecting all USB devices attached to your system.
Your system might well support low-power modes for its USB controllers
while the system is asleep, maintaining the connection, using true sleep
modes like "suspend-to-RAM" or "standby". (Don't write "disk" to the
/sys/power/state file; write "standby" or "mem".) We've not seen any
hardware that can use these modes through software suspend, although in
theory some systems might support "platform" modes that won't break the
USB connections.
Remember that it's always a bad idea to unplug a disk drive containing a
mounted filesystem. That's true even when your system is asleep! The
safest thing is to unmount all filesystems on removable media (such USB,
Firewire, CompactFlash, MMC, external SATA, or even IDE hotplug bays)
before suspending; then remount them after resuming.
There is a work-around for this problem. For more information, see
Documentation/driver-api/usb/persist.rst.
Q: Can I suspend-to-disk using a swap partition under LVM?
A: Yes and No. You can suspend successfully, but the kernel will not be able
to resume on its own. You need an initramfs that can recognize the resume
situation, activate the logical volume containing the swap volume (but not
touch any filesystems!), and eventually call
echo -n "$major:$minor" > /sys/power/resume
where $major and $minor are the respective major and minor device numbers of
the swap volume.
uswsusp works with LVM, too. See http://suspend.sourceforge.net/
Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were
compiled with the similar configuration files. Anyway I found that
suspend to disk (and resume) is much slower on 2.6.16 compared to
2.6.15. Any idea for why that might happen or how can I speed it up?
A: This is because the size of the suspend image is now greater than
for 2.6.15 (by saving more data we can get more responsive system
after resume).
There's the /sys/power/image_size knob that controls the size of the
image. If you set it to 0 (eg. by echo 0 > /sys/power/image_size as
root), the 2.6.15 behavior should be restored. If it is still too
slow, take a look at suspend.sf.net -- userland suspend is faster and
supports LZF compression to speed it up further.

6
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@ -1,5 +1,7 @@
swsusp/S3 tricks
~~~~~~~~~~~~~~~~
================
swsusp/S3 tricks
================
Pavel Machek <pavel@ucw.cz>
If you want to trick swsusp/S3 into working, you might want to try:

55
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View File

@ -1,4 +1,7 @@
=====================================================
Documentation for userland software suspend interface
=====================================================
(C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
First, the warnings at the beginning of swsusp.txt still apply.
@ -30,13 +33,16 @@ called.
The ioctl() commands recognized by the device are:
SNAPSHOT_FREEZE - freeze user space processes (the current process is
SNAPSHOT_FREEZE
freeze user space processes (the current process is
not frozen); this is required for SNAPSHOT_CREATE_IMAGE
and SNAPSHOT_ATOMIC_RESTORE to succeed
SNAPSHOT_UNFREEZE - thaw user space processes frozen by SNAPSHOT_FREEZE
SNAPSHOT_UNFREEZE
thaw user space processes frozen by SNAPSHOT_FREEZE
SNAPSHOT_CREATE_IMAGE - create a snapshot of the system memory; the
SNAPSHOT_CREATE_IMAGE
create a snapshot of the system memory; the
last argument of ioctl() should be a pointer to an int variable,
the value of which will indicate whether the call returned after
creating the snapshot (1) or after restoring the system memory state
@ -45,48 +51,59 @@ SNAPSHOT_CREATE_IMAGE - create a snapshot of the system memory; the
has been created the read() operation can be used to transfer
it out of the kernel
SNAPSHOT_ATOMIC_RESTORE - restore the system memory state from the
SNAPSHOT_ATOMIC_RESTORE
restore the system memory state from the
uploaded snapshot image; before calling it you should transfer
the system memory snapshot back to the kernel using the write()
operation; this call will not succeed if the snapshot
image is not available to the kernel
SNAPSHOT_FREE - free memory allocated for the snapshot image
SNAPSHOT_FREE
free memory allocated for the snapshot image
SNAPSHOT_PREF_IMAGE_SIZE - set the preferred maximum size of the image
SNAPSHOT_PREF_IMAGE_SIZE
set the preferred maximum size of the image
(the kernel will do its best to ensure the image size will not exceed
this number, but if it turns out to be impossible, the kernel will
create the smallest image possible)
SNAPSHOT_GET_IMAGE_SIZE - return the actual size of the hibernation image
SNAPSHOT_GET_IMAGE_SIZE
return the actual size of the hibernation image
SNAPSHOT_AVAIL_SWAP_SIZE - return the amount of available swap in bytes (the
SNAPSHOT_AVAIL_SWAP_SIZE
return the amount of available swap in bytes (the
last argument should be a pointer to an unsigned int variable that will
contain the result if the call is successful).
SNAPSHOT_ALLOC_SWAP_PAGE - allocate a swap page from the resume partition
SNAPSHOT_ALLOC_SWAP_PAGE
allocate a swap page from the resume partition
(the last argument should be a pointer to a loff_t variable that
will contain the swap page offset if the call is successful)
SNAPSHOT_FREE_SWAP_PAGES - free all swap pages allocated by
SNAPSHOT_FREE_SWAP_PAGES
free all swap pages allocated by
SNAPSHOT_ALLOC_SWAP_PAGE
SNAPSHOT_SET_SWAP_AREA - set the resume partition and the offset (in <PAGE_SIZE>
SNAPSHOT_SET_SWAP_AREA
set the resume partition and the offset (in <PAGE_SIZE>
units) from the beginning of the partition at which the swap header is
located (the last ioctl() argument should point to a struct
resume_swap_area, as defined in kernel/power/suspend_ioctls.h,
containing the resume device specification and the offset); for swap
partitions the offset is always 0, but it is different from zero for
swap files (see Documentation/power/swsusp-and-swap-files.txt for
swap files (see Documentation/power/swsusp-and-swap-files.rst for
details).
SNAPSHOT_PLATFORM_SUPPORT - enable/disable the hibernation platform support,
SNAPSHOT_PLATFORM_SUPPORT
enable/disable the hibernation platform support,
depending on the argument value (enable, if the argument is nonzero)
SNAPSHOT_POWER_OFF - make the kernel transition the system to the hibernation
SNAPSHOT_POWER_OFF
make the kernel transition the system to the hibernation
state (eg. ACPI S4) using the platform (eg. ACPI) driver
SNAPSHOT_S2RAM - suspend to RAM; using this call causes the kernel to
SNAPSHOT_S2RAM
suspend to RAM; using this call causes the kernel to
immediately enter the suspend-to-RAM state, so this call must always
be preceded by the SNAPSHOT_FREEZE call and it is also necessary
to use the SNAPSHOT_UNFREEZE call after the system wakes up. This call
@ -98,10 +115,11 @@ SNAPSHOT_S2RAM - suspend to RAM; using this call causes the kernel to
The device's read() operation can be used to transfer the snapshot image from
the kernel. It has the following limitations:
- you cannot read() more than one virtual memory page at a time
- read()s across page boundaries are impossible (ie. if you read() 1/2 of
a page in the previous call, you will only be able to read()
_at_ _most_ 1/2 of the page in the next call)
a page in the previous call, you will only be able to read()
**at most** 1/2 of the page in the next call)
The device's write() operation is used for uploading the system memory snapshot
into the kernel. It has the same limitations as the read() operation.
@ -143,8 +161,10 @@ preferably using mlockall(), before calling SNAPSHOT_FREEZE.
The suspending utility MUST check the value stored by SNAPSHOT_CREATE_IMAGE
in the memory location pointed to by the last argument of ioctl() and proceed
in accordance with it:
1. If the value is 1 (ie. the system memory snapshot has just been
created and the system is ready for saving it):
(a) The suspending utility MUST NOT close the snapshot device
_unless_ the whole suspend procedure is to be cancelled, in
which case, if the snapshot image has already been saved, the
@ -158,6 +178,7 @@ in accordance with it:
called. However, it MAY mount a file system that was not
mounted at that time and perform some operations on it (eg.
use it for saving the image).
2. If the value is 0 (ie. the system state has just been restored from
the snapshot image), the suspending utility MUST close the snapshot
device. Afterwards it will be treated as a regular userland process,

156
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@ -1,7 +1,8 @@
===========================
Video issues with S3 resume
===========================
Video issues with S3 resume
~~~~~~~~~~~~~~~~~~~~~~~~~~~
2003-2006, Pavel Machek
2003-2006, Pavel Machek
During S3 resume, hardware needs to be reinitialized. For most
devices, this is easy, and kernel driver knows how to do
@ -41,37 +42,37 @@ There are a few types of systems where video works after S3 resume:
(1) systems where video state is preserved over S3.
(2) systems where it is possible to call the video BIOS during S3
resume. Unfortunately, it is not correct to call the video BIOS at
that point, but it happens to work on some machines. Use
acpi_sleep=s3_bios.
resume. Unfortunately, it is not correct to call the video BIOS at
that point, but it happens to work on some machines. Use
acpi_sleep=s3_bios.
(3) systems that initialize video card into vga text mode and where
the BIOS works well enough to be able to set video mode. Use
acpi_sleep=s3_mode on these.
the BIOS works well enough to be able to set video mode. Use
acpi_sleep=s3_mode on these.
(4) on some systems s3_bios kicks video into text mode, and
acpi_sleep=s3_bios,s3_mode is needed.
acpi_sleep=s3_bios,s3_mode is needed.
(5) radeon systems, where X can soft-boot your video card. You'll need
a new enough X, and a plain text console (no vesafb or radeonfb). See
http://www.doesi.gmxhome.de/linux/tm800s3/s3.html for more information.
Alternatively, you should use vbetool (6) instead.
a new enough X, and a plain text console (no vesafb or radeonfb). See
http://www.doesi.gmxhome.de/linux/tm800s3/s3.html for more information.
Alternatively, you should use vbetool (6) instead.
(6) other radeon systems, where vbetool is enough to bring system back
to life. It needs text console to be working. Do vbetool vbestate
save > /tmp/delme; echo 3 > /proc/acpi/sleep; vbetool post; vbetool
vbestate restore < /tmp/delme; setfont <whatever>, and your video
should work.
to life. It needs text console to be working. Do vbetool vbestate
save > /tmp/delme; echo 3 > /proc/acpi/sleep; vbetool post; vbetool
vbestate restore < /tmp/delme; setfont <whatever>, and your video
should work.
(7) on some systems, it is possible to boot most of kernel, and then
POSTing bios works. Ole Rohne has patch to do just that at
http://dev.gentoo.org/~marineam/patch-radeonfb-2.6.11-rc2-mm2.
POSTing bios works. Ole Rohne has patch to do just that at
http://dev.gentoo.org/~marineam/patch-radeonfb-2.6.11-rc2-mm2.
(8) on some systems, you can use the video_post utility and or
do echo 3 > /sys/power/state && /usr/sbin/video_post - which will
initialize the display in console mode. If you are in X, you can switch
to a virtual terminal and back to X using CTRL+ALT+F1 - CTRL+ALT+F7 to get
the display working in graphical mode again.
(8) on some systems, you can use the video_post utility and or
do echo 3 > /sys/power/state && /usr/sbin/video_post - which will
initialize the display in console mode. If you are in X, you can switch
to a virtual terminal and back to X using CTRL+ALT+F1 - CTRL+ALT+F7 to get
the display working in graphical mode again.
Now, if you pass acpi_sleep=something, and it does not work with your
bios, you'll get a hard crash during resume. Be careful. Also it is
@ -87,99 +88,126 @@ chance of working.
Table of known working notebooks:
=============================== ===============================================
Model hack (or "how to do it")
------------------------------------------------------------------------------
=============================== ===============================================
Acer Aspire 1406LC ole's late BIOS init (7), turn off DRI
Acer TM 230 s3_bios (2)
Acer TM 242FX vbetool (6)
Acer TM C110 video_post (8)
Acer TM C300 vga=normal (only suspend on console, not in X), vbetool (6) or video_post (8)
Acer TM C300 vga=normal (only suspend on console, not in X),
vbetool (6) or video_post (8)
Acer TM 4052LCi s3_bios (2)
Acer TM 636Lci s3_bios,s3_mode (4)
Acer TM 650 (Radeon M7) vga=normal plus boot-radeon (5) gets text console back
Acer TM 660 ??? (*)
Acer TM 800 vga=normal, X patches, see webpage (5) or vbetool (6)
Acer TM 803 vga=normal, X patches, see webpage (5) or vbetool (6)
Acer TM 650 (Radeon M7) vga=normal plus boot-radeon (5) gets text
console back
Acer TM 660 ??? [#f1]_
Acer TM 800 vga=normal, X patches, see webpage (5)
or vbetool (6)
Acer TM 803 vga=normal, X patches, see webpage (5)
or vbetool (6)
Acer TM 803LCi vga=normal, vbetool (6)
Arima W730a vbetool needed (6)
Asus L2400D s3_mode (3)(***) (S1 also works OK)
Asus L2400D s3_mode (3) [#f2]_ (S1 also works OK)
Asus L3350M (SiS 740) (6)
Asus L3800C (Radeon M7) s3_bios (2) (S1 also works OK)
Asus M6887Ne vga=normal, s3_bios (2), use radeon driver instead of fglrx in x.org
Asus M6887Ne vga=normal, s3_bios (2), use radeon driver
instead of fglrx in x.org
Athlon64 desktop prototype s3_bios (2)
Compal CL-50 ??? (*)
Compal CL-50 ??? [#f1]_
Compaq Armada E500 - P3-700 none (1) (S1 also works OK)
Compaq Evo N620c vga=normal, s3_bios (2)
Dell 600m, ATI R250 Lf none (1), but needs xorg-x11-6.8.1.902-1
Dell D600, ATI RV250 vga=normal and X, or try vbestate (6)
Dell D610 vga=normal and X (possibly vbestate (6) too, but not tested)
Dell Inspiron 4000 ??? (*)
Dell Inspiron 500m ??? (*)
Dell D610 vga=normal and X (possibly vbestate (6) too,
but not tested)
Dell Inspiron 4000 ??? [#f1]_
Dell Inspiron 500m ??? [#f1]_
Dell Inspiron 510m ???
Dell Inspiron 5150 vbetool needed (6)
Dell Inspiron 600m ??? (*)
Dell Inspiron 8200 ??? (*)
Dell Inspiron 8500 ??? (*)
Dell Inspiron 8600 ??? (*)
eMachines athlon64 machines vbetool needed (6) (someone please get me model #s)
HP NC6000 s3_bios, may not use radeonfb (2); or vbetool (6)
HP NX7000 ??? (*)
HP Pavilion ZD7000 vbetool post needed, need open-source nv driver for X
Dell Inspiron 600m ??? [#f1]_
Dell Inspiron 8200 ??? [#f1]_
Dell Inspiron 8500 ??? [#f1]_
Dell Inspiron 8600 ??? [#f1]_
eMachines athlon64 machines vbetool needed (6) (someone please get
me model #s)
HP NC6000 s3_bios, may not use radeonfb (2);
or vbetool (6)
HP NX7000 ??? [#f1]_
HP Pavilion ZD7000 vbetool post needed, need open-source nv
driver for X
HP Omnibook XE3 athlon version none (1)
HP Omnibook XE3GC none (1), video is S3 Savage/IX-MV
HP Omnibook XE3L-GF vbetool (6)
HP Omnibook 5150 none (1), (S1 also works OK)
IBM TP T20, model 2647-44G none (1), video is S3 Inc. 86C270-294 Savage/IX-MV, vesafb gets "interesting" but X work.
IBM TP A31 / Type 2652-M5G s3_mode (3) [works ok with BIOS 1.04 2002-08-23, but not at all with BIOS 1.11 2004-11-05 :-(]
IBM TP T20, model 2647-44G none (1), video is S3 Inc. 86C270-294
Savage/IX-MV, vesafb gets "interesting"
but X work.
IBM TP A31 / Type 2652-M5G s3_mode (3) [works ok with
BIOS 1.04 2002-08-23, but not at all with
BIOS 1.11 2004-11-05 :-(]
IBM TP R32 / Type 2658-MMG none (1)
IBM TP R40 2722B3G ??? (*)
IBM TP R40 2722B3G ??? [#f1]_
IBM TP R50p / Type 1832-22U s3_bios (2)
IBM TP R51 none (1)
IBM TP T30 236681A ??? (*)
IBM TP T30 236681A ??? [#f1]_
IBM TP T40 / Type 2373-MU4 none (1)
IBM TP T40p none (1)
IBM TP R40p s3_bios (2)
IBM TP T41p s3_bios (2), switch to X after resume
IBM TP T42 s3_bios (2)
IBM ThinkPad T42p (2373-GTG) s3_bios (2)
IBM TP X20 ??? (*)
IBM TP X20 ??? [#f1]_
IBM TP X30 s3_bios, s3_mode (4)
IBM TP X31 / Type 2672-XXH none (1), use radeontool (http://fdd.com/software/radeon/) to turn off backlight.
IBM TP X32 none (1), but backlight is on and video is trashed after long suspend. s3_bios,s3_mode (4) works too. Perhaps that gets better results?
IBM TP X31 / Type 2672-XXH none (1), use radeontool
(http://fdd.com/software/radeon/) to
turn off backlight.
IBM TP X32 none (1), but backlight is on and video is
trashed after long suspend. s3_bios,
s3_mode (4) works too. Perhaps that gets
better results?
IBM Thinkpad X40 Type 2371-7JG s3_bios,s3_mode (4)
IBM TP 600e none(1), but a switch to console and back to X is needed
Medion MD4220 ??? (*)
IBM TP 600e none(1), but a switch to console and
back to X is needed
Medion MD4220 ??? [#f1]_
Samsung P35 vbetool needed (6)
Sharp PC-AR10 (ATI rage) none (1), backlight does not switch off
Sony Vaio PCG-C1VRX/K s3_bios (2)
Sony Vaio PCG-F403 ??? (*)
Sony Vaio PCG-F403 ??? [#f1]_
Sony Vaio PCG-GRT995MP none (1), works with 'nv' X driver
Sony Vaio PCG-GR7/K none (1), but needs radeonfb, use radeontool (http://fdd.com/software/radeon/) to turn off backlight.
Sony Vaio PCG-N505SN ??? (*)
Sony Vaio PCG-GR7/K none (1), but needs radeonfb, use
radeontool (http://fdd.com/software/radeon/)
to turn off backlight.
Sony Vaio PCG-N505SN ??? [#f1]_
Sony Vaio vgn-s260 X or boot-radeon can init it (5)
Sony Vaio vgn-S580BH vga=normal, but suspend from X. Console will be blank unless you return to X.
Sony Vaio vgn-S580BH vga=normal, but suspend from X. Console will
be blank unless you return to X.
Sony Vaio vgn-FS115B s3_bios (2),s3_mode (4)
Toshiba Libretto L5 none (1)
Toshiba Libretto 100CT/110CT vbetool (6)
Toshiba Portege 3020CT s3_mode (3)
Toshiba Satellite 4030CDT s3_mode (3) (S1 also works OK)
Toshiba Satellite 4080XCDT s3_mode (3) (S1 also works OK)
Toshiba Satellite 4090XCDT ??? (*)
Toshiba Satellite P10-554 s3_bios,s3_mode (4)(****)
Toshiba Satellite 4090XCDT ??? [#f1]_
Toshiba Satellite P10-554 s3_bios,s3_mode (4)[#f3]_
Toshiba M30 (2) xor X with nvidia driver using internal AGP
Uniwill 244IIO ??? (*)
Uniwill 244IIO ??? [#f1]_
=============================== ===============================================
Known working desktop systems
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
=================== ============================= ========================
Mainboard Graphics card hack (or "how to do it")
------------------------------------------------------------------------------
=================== ============================= ========================
Asus A7V8X nVidia RIVA TNT2 model 64 s3_bios,s3_mode (4)
=================== ============================= ========================
(*) from https://wiki.ubuntu.com/HoaryPMResults, not sure
which options to use. If you know, please tell me.
.. [#f1] from https://wiki.ubuntu.com/HoaryPMResults, not sure
which options to use. If you know, please tell me.
(***) To be tested with a newer kernel.
.. [#f2] To be tested with a newer kernel.
(****) Not with SMP kernel, UP only.
.. [#f3] Not with SMP kernel, UP only.

2
Documentation/process/submitting-drivers.rst
View File

@ -117,7 +117,7 @@ PM support:
implemented") error. You should also try to make sure that your
driver uses as little power as possible when it's not doing
anything. For the driver testing instructions see
Documentation/power/drivers-testing.txt and for a relatively
Documentation/power/drivers-testing.rst and for a relatively
complete overview of the power management issues related to
drivers see :ref:`Documentation/driver-api/pm/devices.rst <driverapi_pm_devices>`.

6
Documentation/scheduler/sched-energy.txt
View File

@ -22,7 +22,7 @@ the highest.
The actual EM used by EAS is _not_ maintained by the scheduler, but by a
dedicated framework. For details about this framework and what it provides,
please refer to its documentation (see Documentation/power/energy-model.txt).
please refer to its documentation (see Documentation/power/energy-model.rst).
2. Background and Terminology
@ -81,7 +81,7 @@ through the arch_scale_cpu_capacity() callback.
The rest of platform knowledge used by EAS is directly read from the Energy
Model (EM) framework. The EM of a platform is composed of a power cost table
per 'performance domain' in the system (see Documentation/power/energy-model.txt
per 'performance domain' in the system (see Documentation/power/energy-model.rst
for futher details about performance domains).
The scheduler manages references to the EM objects in the topology code when the
@ -352,7 +352,7 @@ could be amended in the future if proven otherwise.
EAS uses the EM of a platform to estimate the impact of scheduling decisions on
energy. So, your platform must provide power cost tables to the EM framework in
order to make EAS start. To do so, please refer to documentation of the
independent EM framework in Documentation/power/energy-model.txt.
independent EM framework in Documentation/power/energy-model.rst.
Please also note that the scheduling domains need to be re-built after the
EM has been registered in order to start EAS.

2
Documentation/trace/coresight-cpu-debug.txt
View File

@ -151,7 +151,7 @@ At the runtime you can disable idle states with below methods:
It is possible to disable CPU idle states by way of the PM QoS
subsystem, more specifically by using the "/dev/cpu_dma_latency"
interface (see Documentation/power/pm_qos_interface.txt for more
interface (see Documentation/power/pm_qos_interface.rst for more
details). As specified in the PM QoS documentation the requested
parameter will stay in effect until the file descriptor is released.
For example:

2
Documentation/translations/zh_CN/process/submitting-drivers.rst
View File

@ -97,7 +97,7 @@ Linux 2.6:
函数定义成返回 -ENOSYS（功能未实现）错误。你还应该尝试确
保你的驱动在什么都不干的情况下将耗电降到最低。要获得驱动
程序测试的指导，请参阅
Documentation/power/drivers-testing.txt。有关驱动程序电
Documentation/power/drivers-testing.rst。有关驱动程序电
源管理问题相对全面的概述，请参阅
Documentation/driver-api/pm/devices.rst。

4
MAINTAINERS
View File

@ -6446,7 +6446,7 @@ M: "Rafael J. Wysocki" <rjw@rjwysocki.net>
M: Pavel Machek <pavel@ucw.cz>
L: linux-pm@vger.kernel.org
S: Supported
F: Documentation/power/freezing-of-tasks.txt
F: Documentation/power/freezing-of-tasks.rst
F: include/linux/freezer.h
F: kernel/freezer.c
@ -11764,7 +11764,7 @@ S: Maintained
T: git git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm.git
F: drivers/opp/
F: include/linux/pm_opp.h
F: Documentation/power/opp.txt
F: Documentation/power/opp.rst
F: Documentation/devicetree/bindings/opp/
OPL4 DRIVER

2
arch/x86/Kconfig
View File

@ -2447,7 +2447,7 @@ menuconfig APM
machines with more than one CPU.
In order to use APM, you will need supporting software. For location
and more information, read <file:Documentation/power/apm-acpi.txt>
and more information, read <file:Documentation/power/apm-acpi.rst>
and the Battery Powered Linux mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>.

2
drivers/gpu/drm/i915/i915_drv.h
View File

@ -1175,7 +1175,7 @@ struct skl_wm_params {
* to be disabled. This shouldn't happen and we'll print some error messages in
* case it happens.
*
* For more, read the Documentation/power/runtime_pm.txt.
* For more, read the Documentation/power/runtime_pm.rst.
*/
struct i915_runtime_pm {
atomic_t wakeref_count;

2
drivers/opp/Kconfig
View File

@ -10,4 +10,4 @@ config PM_OPP
OPP layer organizes the data internally using device pointers
representing individual voltage domains and provides SOC
implementations a ready to use framework to manage OPPs.
For more information, read <file:Documentation/power/opp.txt>
For more information, read <file:Documentation/power/opp.rst>

2
drivers/power/supply/power_supply_core.c
View File

@ -607,7 +607,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
/* The property and field names below must correspond to elements
* in enum power_supply_property. For reasoning, see
* Documentation/power/power_supply_class.txt.
* Documentation/power/power_supply_class.rst.
*/
of_property_read_u32(battery_np, "energy-full-design-microwatt-hours",

2
include/linux/interrupt.h
View File

@ -52,7 +52,7 @@
* irq line disabled until the threaded handler has been run.
* IRQF_NO_SUSPEND - Do not disable this IRQ during suspend. Does not guarantee
* that this interrupt will wake the system from a suspended
* state. See Documentation/power/suspend-and-interrupts.txt
* state. See Documentation/power/suspend-and-interrupts.rst
* IRQF_FORCE_RESUME - Force enable it on resume even if IRQF_NO_SUSPEND is set
* IRQF_NO_THREAD - Interrupt cannot be threaded
* IRQF_EARLY_RESUME - Resume IRQ early during syscore instead of at device

2
include/linux/pci.h
View File

@ -807,7 +807,7 @@ struct module;
* @suspend_late: Put device into low power state.
* @resume_early: Wake device from low power state.
* @resume: Wake device from low power state.
* (Please see Documentation/power/pci.txt for descriptions
* (Please see Documentation/power/pci.rst for descriptions
* of PCI Power Management and the related functions.)
* @shutdown: Hook into reboot_notifier_list (kernel/sys.c).
* Intended to stop any idling DMA operations.

2
include/linux/pm.h
View File

@ -284,7 +284,7 @@ typedef struct pm_message {
* actions to be performed by a device driver's callbacks generally depend on
* the platform and subsystem the device belongs to.
*
* Refer to Documentation/power/runtime_pm.txt for more information about the
* Refer to Documentation/power/runtime_pm.rst for more information about the
* role of the @runtime_suspend(), @runtime_resume() and @runtime_idle()
* callbacks in device runtime power management.
*/

6
kernel/power/Kconfig
View File

@ -65,7 +65,7 @@ config HIBERNATION
need to run mkswap against the swap partition used for the suspend.
It also works with swap files to a limited extent (for details see
<file:Documentation/power/swsusp-and-swap-files.txt>).
<file:Documentation/power/swsusp-and-swap-files.rst>).
Right now you may boot without resuming and resume later but in the
meantime you cannot use the swap partition(s)/file(s) involved in
@ -74,7 +74,7 @@ config HIBERNATION
MOUNT any journaled filesystems mounted before the suspend or they
will get corrupted in a nasty way.
For more information take a look at <file:Documentation/power/swsusp.txt>.
For more information take a look at <file:Documentation/power/swsusp.rst>.
config ARCH_SAVE_PAGE_KEYS
bool
@ -255,7 +255,7 @@ config APM_EMULATION
notification of APM "events" (e.g. battery status change).
In order to use APM, you will need supporting software. For location
and more information, read <file:Documentation/power/apm-acpi.txt>
and more information, read <file:Documentation/power/apm-acpi.rst>
and the Battery Powered Linux mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>.

2
net/wireless/Kconfig
View File

@ -165,7 +165,7 @@ config CFG80211_DEFAULT_PS
If this causes your applications to misbehave you should fix your
applications instead -- they need to register their network
latency requirement, see Documentation/power/pm_qos_interface.txt.
latency requirement, see Documentation/power/pm_qos_interface.rst.
config CFG80211_DEBUGFS
bool "cfg80211 DebugFS entries"