mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-21 12:06:48 +07:00
188 lines
6.4 KiB
Plaintext
188 lines
6.4 KiB
Plaintext
Kernel driver ds1621
|
|
====================
|
|
|
|
Supported chips:
|
|
* Dallas Semiconductor / Maxim Integrated DS1621
|
|
Prefix: 'ds1621'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available from www.maximintegrated.com
|
|
|
|
* Dallas Semiconductor DS1625
|
|
Prefix: 'ds1625'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available from www.datasheetarchive.com
|
|
|
|
* Maxim Integrated DS1631
|
|
Prefix: 'ds1631'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available from www.maximintegrated.com
|
|
|
|
* Maxim Integrated DS1721
|
|
Prefix: 'ds1721'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available from www.maximintegrated.com
|
|
|
|
* Maxim Integrated DS1731
|
|
Prefix: 'ds1731'
|
|
Addresses scanned: none
|
|
Datasheet: Publicly available from www.maximintegrated.com
|
|
|
|
Authors:
|
|
Christian W. Zuckschwerdt <zany@triq.net>
|
|
valuable contributions by Jan M. Sendler <sendler@sendler.de>
|
|
ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net>
|
|
with the help of Jean Delvare <jdelvare@suse.de>
|
|
|
|
Module Parameters
|
|
------------------
|
|
|
|
* polarity int
|
|
Output's polarity: 0 = active high, 1 = active low
|
|
|
|
Description
|
|
-----------
|
|
|
|
The DS1621 is a (one instance) digital thermometer and thermostat. It has
|
|
both high and low temperature limits which can be user defined (i.e.
|
|
programmed into non-volatile on-chip registers). Temperature range is -55
|
|
degree Celsius to +125 in 0.5 increments. You may convert this into a
|
|
Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity
|
|
parameter is not provided, original value is used.
|
|
|
|
As for the thermostat, behavior can also be programmed using the polarity
|
|
toggle. On the one hand ("heater"), the thermostat output of the chip,
|
|
Tout, will trigger when the low limit temperature is met or underrun and
|
|
stays high until the high limit is met or exceeded. On the other hand
|
|
("cooler"), vice versa. That way "heater" equals "active low", whereas
|
|
"conditioner" equals "active high". Please note that the DS1621 data sheet
|
|
is somewhat misleading in this point since setting the polarity bit does
|
|
not simply invert Tout.
|
|
|
|
A second thing is that, during extensive testing, Tout showed a tolerance
|
|
of up to +/- 0.5 degrees even when compared against precise temperature
|
|
readings. Be sure to have a high vs. low temperature limit gap of al least
|
|
1.0 degree Celsius to avoid Tout "bouncing", though!
|
|
|
|
The alarm bits are set when the high or low limits are met or exceeded and
|
|
are reset by the module as soon as the respective temperature ranges are
|
|
left.
|
|
|
|
The alarm registers are in no way suitable to find out about the actual
|
|
status of Tout. They will only tell you about its history, whether or not
|
|
any of the limits have ever been met or exceeded since last power-up or
|
|
reset. Be aware: When testing, it showed that the status of Tout can change
|
|
with neither of the alarms set.
|
|
|
|
Since there is no version or vendor identification register, there is
|
|
no unique identification for these devices. Therefore, explicit device
|
|
instantiation is required for correct device identification and functionality
|
|
(one device per address in this address range: 0x48..0x4f).
|
|
|
|
The DS1625 is pin compatible and functionally equivalent with the DS1621,
|
|
but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are
|
|
also pin compatible with the DS1621 and provide multi-resolution support.
|
|
|
|
Additionally, the DS1721 data sheet says the temperature flags (THF and TLF)
|
|
are used internally, however, these flags do get set and cleared as the actual
|
|
temperature crosses the min or max settings (which by default are set to 75
|
|
and 80 degrees respectively).
|
|
|
|
Temperature Conversion:
|
|
-----------------------
|
|
DS1621 - 750ms (older devices may take up to 1000ms)
|
|
DS1625 - 500ms
|
|
DS1631 - 93ms..750ms for 9..12 bits resolution, respectively.
|
|
DS1721 - 93ms..750ms for 9..12 bits resolution, respectively.
|
|
DS1731 - 93ms..750ms for 9..12 bits resolution, respectively.
|
|
|
|
Note:
|
|
On the DS1621, internal access to non-volatile registers may last for 10ms
|
|
or less (unverified on the other devices).
|
|
|
|
Temperature Accuracy:
|
|
---------------------
|
|
DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees)
|
|
DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees)
|
|
DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees)
|
|
DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees)
|
|
DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees)
|
|
|
|
Note:
|
|
Please refer to the device datasheets for accuracy at other temperatures.
|
|
|
|
Temperature Resolution:
|
|
-----------------------
|
|
As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution
|
|
support, which is achieved via the R0 and R1 config register bits, where:
|
|
|
|
R0..R1
|
|
------
|
|
0 0 => 9 bits, 0.5 degrees Celcius
|
|
1 0 => 10 bits, 0.25 degrees Celcius
|
|
0 1 => 11 bits, 0.125 degrees Celcius
|
|
1 1 => 12 bits, 0.0625 degrees Celcius
|
|
|
|
Note:
|
|
At initial device power-on, the default resolution is set to 12-bits.
|
|
|
|
The resolution mode for the DS1631, DS1721, or DS1731 can be changed from
|
|
userspace, via the device 'update_interval' sysfs attribute. This attribute
|
|
will normalize the range of input values to the device maximum resolution
|
|
values defined in the datasheet as follows:
|
|
|
|
Resolution Conversion Time Input Range
|
|
(C/LSB) (msec) (msec)
|
|
------------------------------------------------
|
|
0.5 93.75 0....94
|
|
0.25 187.5 95...187
|
|
0.125 375 188..375
|
|
0.0625 750 376..infinity
|
|
------------------------------------------------
|
|
|
|
The following examples show how the 'update_interval' attribute can be
|
|
used to change the conversion time:
|
|
|
|
$ cat update_interval
|
|
750
|
|
$ cat temp1_input
|
|
22062
|
|
$
|
|
$ echo 300 > update_interval
|
|
$ cat update_interval
|
|
375
|
|
$ cat temp1_input
|
|
22125
|
|
$
|
|
$ echo 150 > update_interval
|
|
$ cat update_interval
|
|
188
|
|
$ cat temp1_input
|
|
22250
|
|
$
|
|
$ echo 1 > update_interval
|
|
$ cat update_interval
|
|
94
|
|
$ cat temp1_input
|
|
22000
|
|
$
|
|
$ echo 1000 > update_interval
|
|
$ cat update_interval
|
|
750
|
|
$ cat temp1_input
|
|
22062
|
|
$
|
|
|
|
As shown, the ds1621 driver automatically adjusts the 'update_interval'
|
|
user input, via a step function. Reading back the 'update_interval' value
|
|
after a write operation provides the conversion time used by the device.
|
|
|
|
Mathematically, the resolution can be derived from the conversion time
|
|
via the following function:
|
|
|
|
g(x) = 0.5 * [minimum_conversion_time/x]
|
|
|
|
where:
|
|
-> 'x' = the output from 'update_interval'
|
|
-> 'g(x)' = the resolution in degrees C per LSB.
|
|
-> 93.75ms = minimum conversion time
|