powerpc/powernv: Add documentation for the opal sensor_groups sysfs interfaces

Commit bf9571550f ("powerpc/powernv: Add support to clear sensor
groups data") added a mechanism to clear sensor-group data via a sysfs
interface. However, the ABI for that interface has not been
documented.

This patch documents the ABI for the sysfs interface for sensor-groups
and clearing the sensor-groups.

This patch was originally sent by Shilpasri G Bhat on the mailing list:
https://lkml.org/lkml/2018/8/1/85

Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1574776274-22355-1-git-send-email-ego@linux.vnet.ibm.com
This commit is contained in:
Shilpasri G Bhat 2019-11-26 19:21:14 +05:30 committed by Michael Ellerman
parent 9686813f6e
commit 32377bd2cb

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What: /sys/firmware/opal/sensor_groups
Date: August 2017
Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
Description: Sensor groups directory for POWER9 powernv servers
Each folder in this directory contains a sensor group
which are classified based on type of the sensor
like power, temperature, frequency, current, etc. They
can also indicate the group of sensors belonging to
different owners like CSM, Profiler, Job-Scheduler
What: /sys/firmware/opal/sensor_groups/<sensor_group_name>/clear
Date: August 2017
Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
Description: Sysfs file to clear the min-max of all the sensors
belonging to the group.
Writing 1 to this file will clear the minimum and
maximum values of all the sensors in the group.
In POWER9, the min-max of a sensor is the historical minimum
and maximum value of the sensor cached by OCC.