[PATCH v8 13/13] Documentation: amd-pstate: introduce new global sysfs attributes

[Perry Yuan <perry.yuan@amd.com>]

The new amd-pstate driver support to switch the driver working mode and
use can switch the driver mode within the sysfs attributes in the below
path and check current mode

$ cd /sys/devices/system/cpu/amd-pstate

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

switch mode:
$ sudo bash -c "echo passive  > /sys/devices/system/cpu/amd-pstate/status"
or
$ sudo bash -c "echo active  > /sys/devices/system/cpu/amd-pstate/status"

Signed-off-by: Perry Yuan <perry.yuan@amd.com>
---
 Documentation/admin-guide/pm/amd-pstate.rst | 28 +++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index 62744dae3c5f..f3a8f8a66783 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -339,6 +339,34 @@ 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 "off".
+
+	"active"
+		The driver is functional and in the ``active mode``
+
+	"passive"
+		The driver is functional and in the ``passive mode``
+
+	"off"
+		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, the write will
+	cause the driver to switch over to the operation mode represented by
+	that string - or to be unregistered in the "off" case.
+
 ``cpupower`` tool support for ``amd-pstate``
 ===============================================
 
-- 
2.34.1