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:

quoted

From: Jae Hyun Yoo <redacted>

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 <redacted>
Co-developed-by: Iwona Winiarska <iwona.winiarska@intel.com>
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Reviewed-by: Pierre-Louis Bossart <redacted>
---
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 [off-list ref]
+
+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.

quoted

+temp2_max              Provides thermal control temperature of the CPU
package
+                       which is also known as Tcontrol.
+temp2_crit             Provides shutdown temperature of the CPU package which
+                       is also known as the maximum processor junction
+                       temperature, Tjmax or Tprochot.
+temp2_crit_hyst                Provides the hysteresis value from Tcontrol to
Tjmax of
+                       the CPU package.
+
+temp3_label            "Tcontrol"
+temp3_input            Provides current Tcontrol temperature of the CPU
+                       package which is also known as Fan Temperature target.
+                       Indicates the relative value from thermal monitor trip
+                       temperature at which fans should be engaged.
+temp3_crit             Provides Tcontrol critical value of the CPU package
+                       which is same to Tjmax.
+
+temp4_label            "Tthrottle"
+temp4_input            Provides current Tthrottle temperature of the CPU
+                       package. Used for throttling temperature. If this
value
+                       is allowed and lower than Tjmax - the throttle will
+                       occur and reported at lower than Tjmax.
+
+temp5_label            "Tjmax"
+temp5_input            Provides the maximum junction temperature, Tjmax of
the
+                       CPU package.
+
+temp[6-N]_label                Provides string "Core X", where X is resolved
core
+                       number.
+temp[6-N]_input                Provides current temperature of each core.
+temp[6-N]_max          Provides thermal control temperature of the core.
+temp[6-N]_crit         Provides shutdown temperature of the core.
+temp[6-N]_crit_hyst    Provides the hysteresis value from Tcontrol to Tjmax
of
+                       the core.

I only see *_label and *_input for the per-core temperature sensors, no
*_max, *_crit, or *_crit_hyst.

You're right - this should be removed from documentation.

quoted

+
+=======================
=======================================================

diff --git a/Documentation/hwmon/peci-dimmtemp.rst b/Documentation/hwmon/peci-

dimmtemp.rst
new file mode 100644
index 000000000000..1778d9317e43

--- /dev/null
+++ b/Documentation/hwmon/peci-dimmtemp.rst

@@ -0,0 +1,58 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver peci-dimmtemp
+===========================
+
+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 [off-list ref]
+
+Description
+-----------
+
+This driver implements a generic PECI hwmon feature which provides Digital
+Thermal Sensor (DTS) thermal readings of DIMM components that are accessible
+via the processor PECI interface.

I had thought "DTS" referred to a fairly specific sensor in the CPU; is
the same term also used for DIMM temp sensors or is the mention of it
here a copy/paste error?

Yeah - it should be "Temperature Sensor on DIMM".

Thanks
-Iwona

quoted

+
+All temperature values are given in millidegree Celsius and will be
measurable
+only when the target CPU is powered on.
+
+Sysfs interface
+-------------------
+
+=======================
=======================================================
+
+temp[N]_label          Provides string "DIMM CI", where C is DIMM channel and
+                       I is DIMM index of the populated DIMM.
+temp[N]_input          Provides current temperature of the populated DIMM.
+temp[N]_max            Provides thermal control temperature of the DIMM.
+temp[N]_crit           Provides shutdown temperature of the DIMM.
+
+=======================
=======================================================
+
+Note:
+       DIMM temperature attributes will appear when the client CPU's BIOS
+       completes memory training and testing.

diff --git a/MAINTAINERS b/MAINTAINERS
index 35ba9e3646bd..d16da127bbdc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -14509,6 +14509,8 @@ M:      Iwona Winiarska <iwona.winiarska@intel.com>

R:      Jae Hyun Yoo [off-list ref]
L:      linux-hwmon@vger.kernel.org
S:      Supported
+F:     Documentation/hwmon/peci-cputemp.rst
+F:     Documentation/hwmon/peci-dimmtemp.rst
F:      drivers/hwmon/peci/

PECI SUBSYSTEM
-- 
2.31.1