[PATCH v10 12/12] Documentation: amd-pstate: introduce new global sysfs attributes

Perry Yuan
2023-01-06T06:17:06Z

The amd-pstate driver supports switching working modes at runtime.
Users can view and change modes by interacting with the "status" sysfs
attribute.

1) check driver mode:
$ cat /sys/devices/system/cpu/amd-pstate/status

2) switch mode:
`# echo "passive" | sudo tee /sys/devices/system/cpu/amd-pstate/status`
or
`# echo "active" | sudo tee /sys/devices/system/cpu/amd-pstate/status`

Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Perry Yuan <perry.yuan@amd.com>
---
Documentation/admin-guide/pm/amd-pstate.rst | 29 +++++++++++++++++++++
1 file changed, 29 insertions(+)

diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index 62744dae3c5f..df0637a49f47 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -339,6 +339,35 @@ processor must provide at least nominal performance requested and go higher if c
operating conditions allow.

+User Space Interface in ``sysfs``
+=================================
+
+Global Attributes
+-----------------
+
+``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to
+control its functionality at the system level. They are located in the
+``/sys/devices/system/cpu/amd-pstate/`` directory and affect all CPUs.
+
+``status``
+ Operation mode of the driver: "active", "passive" or "disable".
+
+ "active"
+ The driver is functional and in the ``active mode``
+
+ "passive"
+ The driver is functional and in the ``passive mode``
+
+ "disable"
+ The driver is unregistered and not functional now.
+
+ This attribute can be written to in order to change the driver's
+ operation mode or to unregister it. The string written to it must be
+ one of the possible values of it and, if successful, writing one of
+ these values to the sysfs file will cause the driver to switch over
+ to the operation mode represented by that string - or to be
+ unregistered in the "disable" case.
+
``cpupower`` tool support for ``amd-pstate``
===============================================

--
2.34.1