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

Commit bf9571550f52 ("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

diff --git a/Documentation/ABI/testing/sysfs-firmware-opal-sensor-groups b/Documentation/ABI/testing/sysfs-firmware-opal-sensor-groups
new file mode 100644 (file)
index 0000000..3a2dfe5
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-opal-sensor-groups
@@ -0,0 +1,21 @@
+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.