Messages in this thread | | | Subject | Re: [PATCH 13/14] docs: hwmon: Document PECI drivers | From | Guenter Roeck <> | Date | Wed, 4 Aug 2021 11:05:48 -0700 |
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On 8/4/21 10:52 AM, Zev Weiss wrote: > On Mon, Aug 02, 2021 at 06:37:30AM CDT, Winiarska, Iwona wrote: >> On Tue, 2021-07-27 at 22:58 +0000, Zev Weiss wrote: >>> On Mon, Jul 12, 2021 at 05:04:46PM CDT, Iwona Winiarska wrote: >>>> From: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> >>>> >>>> Add documentation for peci-cputemp driver that provides DTS thermal >>>> readings for CPU packages and CPU cores and peci-dimmtemp driver that >>>> provides DTS thermal readings for DIMMs. >>>> >>>> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> >>>> Co-developed-by: Iwona Winiarska <iwona.winiarska@intel.com> >>>> Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com> >>>> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> >>>> --- >>>> Documentation/hwmon/index.rst | 2 + >>>> Documentation/hwmon/peci-cputemp.rst | 93 +++++++++++++++++++++++++++ >>>> Documentation/hwmon/peci-dimmtemp.rst | 58 +++++++++++++++++ >>>> MAINTAINERS | 2 + >>>> 4 files changed, 155 insertions(+) >>>> create mode 100644 Documentation/hwmon/peci-cputemp.rst >>>> create mode 100644 Documentation/hwmon/peci-dimmtemp.rst >>>> >>>> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst >>>> index bc01601ea81a..cc76b5b3f791 100644 >>>> --- a/Documentation/hwmon/index.rst >>>> +++ b/Documentation/hwmon/index.rst >>>> @@ -154,6 +154,8 @@ Hardware Monitoring Kernel Drivers >>>> pcf8591 >>>> pim4328 >>>> pm6764tr >>>> + peci-cputemp >>>> + peci-dimmtemp >>>> pmbus >>>> powr1220 >>>> pxe1610 >>>> diff --git a/Documentation/hwmon/peci-cputemp.rst >>>> b/Documentation/hwmon/peci-cputemp.rst >>>> new file mode 100644 >>>> index 000000000000..d3a218ba810a >>>> --- /dev/null >>>> +++ b/Documentation/hwmon/peci-cputemp.rst >>>> @@ -0,0 +1,93 @@ >>>> +.. SPDX-License-Identifier: GPL-2.0-only >>>> + >>>> +Kernel driver peci-cputemp >>>> +========================== >>>> + >>>> +Supported chips: >>>> + One of Intel server CPUs listed below which is connected to a PECI >>>> bus. >>>> + * Intel Xeon E5/E7 v3 server processors >>>> + Intel Xeon E5-14xx v3 family >>>> + Intel Xeon E5-24xx v3 family >>>> + Intel Xeon E5-16xx v3 family >>>> + Intel Xeon E5-26xx v3 family >>>> + Intel Xeon E5-46xx v3 family >>>> + Intel Xeon E7-48xx v3 family >>>> + Intel Xeon E7-88xx v3 family >>>> + * Intel Xeon E5/E7 v4 server processors >>>> + Intel Xeon E5-16xx v4 family >>>> + Intel Xeon E5-26xx v4 family >>>> + Intel Xeon E5-46xx v4 family >>>> + Intel Xeon E7-48xx v4 family >>>> + Intel Xeon E7-88xx v4 family >>>> + * Intel Xeon Scalable server processors >>>> + Intel Xeon D family >>>> + Intel Xeon Bronze family >>>> + Intel Xeon Silver family >>>> + Intel Xeon Gold family >>>> + Intel Xeon Platinum family >>>> + >>>> + Datasheet: Available from http://www.intel.com/design/literature.htm >>>> + >>>> +Author: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> >>>> + >>>> +Description >>>> +----------- >>>> + >>>> +This driver implements a generic PECI hwmon feature which provides Digital >>>> +Thermal Sensor (DTS) thermal readings of the CPU package and CPU cores that >>>> are >>>> +accessible via the processor PECI interface. >>>> + >>>> +All temperature values are given in millidegree Celsius and will be >>>> measurable >>>> +only when the target CPU is powered on. >>>> + >>>> +Sysfs interface >>>> +------------------- >>>> + >>>> +======================= >>>> ======================================================= >>>> +temp1_label "Die" >>>> +temp1_input Provides current die temperature of the CPU package. >>>> +temp1_max Provides thermal control temperature of the CPU >>>> package >>>> + which is also known as Tcontrol. >>>> +temp1_crit Provides shutdown temperature of the CPU package >>>> which >>>> + is also known as the maximum processor junction >>>> + temperature, Tjmax or Tprochot. >>>> +temp1_crit_hyst Provides the hysteresis value from Tcontrol >>>> to Tjmax of >>>> + the CPU package. >>>> + >>>> +temp2_label "DTS" >>>> +temp2_input Provides current DTS temperature of the CPU package. >>> >>> Would this be a good place to note the slightly counter-intuitive nature >>> of DTS readings? i.e. add something along the lines of "The DTS sensor >>> produces a delta relative to Tjmax, so negative values are normal and >>> values approaching zero are hot." (In my experience people who aren't >>> already familiar with it tend to think something's wrong when a CPU >>> temperature reading shows -50C.) >> >> I believe that what you're referring to is a result of "GetTemp", and we're >> using it to calculate "Die" sensor values (temp1). >> The sensor value is absolute - we don't expose "raw" thermal sensor value >> (delta) anywhere. >> >> DTS sensor is exposing temperature value scaled to fit DTS 2.0 thermal profile: >> https://www.intel.com/content/www/us/en/processors/xeon/scalable/xeon-scalable-thermal-guide.html >> (section 5.2.3.2) >> >> Similar to "Die" sensor - it's also exposed in absolute form. >> >> I'll try to change description to avoid confusion. >> > > When I tested the patch series by applying it to my OpenBMC kernel, the > temp2_input sysfs file produced negative numbers (as has been the case > with previous iterations of the PECI patchset). Is that expected? From > what Guenter has said it sounds like that's going to need to change so > that the temperature readings are all in "normal" millidegrees C > (that is, relative to the freezing point of water). >
Correct, the temperature is expected to be reported in millidegrees C per hwmon ABI. Everything else is unacceptable. That makes me wonder what "raw" and "absolute" means. Negative numbers suggest that, whatever is reported today, it is not millidegrees C.
Guenter
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