Recently cpufreq support on my laptop (Lenovo T60) broke completely: when
it's plugged into AC it would never go higher than 1 GHz - neither 1.3 GHz
nor 1.83 GHz is possible - no matter which governor (userspace, speed or
ondemand) is used.
After some cpufreq debugging i tracked the regression back to the following
(totally correct) bug-fix commit:
commit 0916bd3ebb
Author: Dave Jones <davej@redhat.com>
Date: Wed Nov 22 20:42:01 2006 -0500
[PATCH] Correct bound checking from the value returned from _PPC method.
This bugfix, which makes other laptops work, made a previously hidden
(BIOS) bug visible on my laptop.
The bug is the following: if the _PPC (Performance Present Capabilities)
optional ACPI object is queried /after/ bootup then the BIOS reports an
incorrect value of '2'.
My laptop (Lenovo T60) has the following performance states supported:
0: 1833000
1: 1333000
2: 1000000
Per ACPI specification, a _PPC value of '0' means that all 3 performance
states are usable. A _PPC value of '1' means states 1 .. 2 are usable, a
value of '2' means only state '2' (slowest) is usable.
now, the _PPC object is optional, and it also comes with notification.
Furthermore, when a CPU object is initialized, the _PPC object is
initialized as well. So the following evaluation of the _PPC object is
superfluous:
[<c028ba5f>] acpi_processor_get_platform_limit+0xa1/0xaf
[<c028c040>] acpi_processor_register_performance+0x3b9/0x3ef
[<c0111a85>] acpi_cpufreq_cpu_init+0xb7/0x596
[<c03dab74>] cpufreq_add_dev+0x160/0x4a8
[<c02bed90>] sysdev_driver_register+0x5a/0xa0
[<c03d9c4c>] cpufreq_register_driver+0xb4/0x176
[<c068ac08>] acpi_cpufreq_init+0xe5/0xeb
[<c010056e>] init+0x14f/0x3dd
And this is the point where my laptop's BIOS returns the incorrect value of
'2'. Note that it has not sent any notification event, so the value is
probably not really intentional (possibly spurious), and Windows likely
doesnt query it after bootup either. Maybe the value is kept at '2'
normally, and is only set to the real value when a true asynchronous event
(such as AC plug event, battery switch, etc.) occurs.
So i /think/ this is a grey area of the ACPI spec: per the letter of the
spec the _PPC value only changes when notified, so there's no reason to
query it after the system has booted up. So in my opinion the best (and
most compatible) strategy would be to do the change below, and to not
evaluate the _PPC object in the acpi_processor_get_performance_info() call,
but only evaluate it if _PPC is present during CPU object init, or if it's
notified during an asynchronous event. This change is more permissive than
the previous logic, so it definitely shouldnt break any existing system.
This also happens to fix my laptop, which is merrily chugging along at
1.83 GHz now. Yay!
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Dave Jones <davej@redhat.com>
Acked-by: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
processor_perflib.c::acpi_processor_ppc_notifier() check if the value
returned by the processor's _PPC method is 0 and return failed if so.
This is wrong since 0 indicate that the bios think the processor can go
to the highest frequency. This patch for example fix the HP NX 6125 to
allow its highest frequency to be available.
Signed-off-by: Bruno Ducrot <ducrot@poupinou.org>
Cc: "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Treat HW coordination as independent CPUs.
This enables per-cpu monintoring of P-states
http://bugzilla.kernel.org/show_bug.cgi?id=5737
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
From: Andrew Morton <akpm@osdl.org>
Work around the oops reported in
http://bugzilla.kernel.org/show_bug.cgi?id=6478.
Thanks to Ralf Hildebrandt <ralf.hildebrandt@charite.de> for testing and
reporting.
Acked-by: Dave Jones <davej@codemonkey.org.uk>
Cc: "Brown, Len" <len.brown@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
for_each_cpu() actually iterates across all possible CPUs. We've had mistakes
in the past where people were using for_each_cpu() where they should have been
iterating across only online or present CPUs. This is inefficient and
possibly buggy.
We're renaming for_each_cpu() to for_each_possible_cpu() to avoid this in the
future.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>
Semaphore to mutex conversion.
The conversion was generated via scripts, and the result was validated
automatically via a script as well.
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>
acpi_processor_limit_fops.write was written at run time,
but can be initiailized at compile-time instead.
Similar for acpi_video_bus_POST_fops.write and friends,
but keep doing those at runtime to avoid prototype-hell.
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Len Brown <len.brown@intel.com>
Linux invokes the AML _PDC method (Processor Driver Capabilities)
to tell the BIOS what features it can handle. While the ACPI
spec says nothing about the OS invoking _PDC multiple times,
doing so with changing bits seems to hopelessly confuse the BIOS
on multiple platforms up to and including crashing the system.
Factor out the _PDC invocation so Linux invokes it only once.
http://bugzilla.kernel.org/show_bug.cgi?id=5483
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
