Re: [PATCH 13/14] docs: hwmon: Document PECI drivers

["Winiarska, Iwona" <iwona.winiarska@intel.com>]

On Tue, 2021-07-27 at 17:49 -0700, Guenter Roeck wrote:
> On 7/27/21 3:58 PM, 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.)
> > 
> 
> All attributes shall follow the ABI, and the driver must translate reported
> values to degrees C. If those sensors do not follow the ABI and report something
> else, I won't accept the driver.
> 
> Guenter

Sure, I believe all attributes already follow the ABI and the reported values
are in millidegree Celsius.

Thanks
-Iwona
>