[PATCH 4/4] Documentation: amd_pstate: Add amd_pstate state sysfs file

Wyes Karny
2022-12-07T15:50:43Z

Add documentation for amd_pstate `state` interface.
User can see the current state of the driver with the help of this sysfs
interface:
# cat /sys/devices/system/cpu/amd_pstate/state
# disable [passive] guided

User can load/unload driver with the help of `state` sysfs interface.
- Load driver with passive mode:
# echo passive > /sys/devices/system/cpu/amd_pstate/state
- Unload the driver:
# echo disable > /sys/devices/system/cpu/amd_pstate/state
- To switch to guided mode:
# echo guided > /sys/devices/system/cpu/amd_pstate/state

Signed-off-by: Wyes Karny <wyes.karny@amd.com>
---
Documentation/admin-guide/pm/amd-pstate.rst | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index 06e23538f79c..4d3783516ddc 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -265,6 +265,17 @@ This attribute is read-only.
Other performance and frequency values can be read back from
``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`.

+``state``
+
+``amd_pstate`` also exposes a sysfs interface to view and control the driver state.
+The driver state can be one of the following:
+``disable`` : indicates driver is in unloaded state.
+``passive`` : indicates driver is loaded and currently in passive mode.
+``guided`` : indicates driver is loaded and currenlty in guided autonomous mode.
+This file can be found here: ``/sys/devices/system/cpu/amd_pstate/state``.
+
+To switch to passive mode: ``echo passive > /sys/devices/system/cpu/amd_pstate/state``
+To switch to guided mode: ``echo guided > /sys/devices/system/cpu/amd_pstate/state``

``amd-pstate`` vs ``acpi-cpufreq``
======================================
--
2.34.1