@@ -339,6 +339,44 @@ 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.
+
+``cppc_dynamic_boost``
+ This attribute is only present if ``amd-pstate`` works in the
+ `active mode` in the processor. If set to 1, it will cause
+ the minimum P-state limit to be increased dynamically for a short time
+ whenever a task previously waiting on I/O is selected to run on a given
+ logical CPU (the purpose of this mechanism is to improve performance).
+ when the I/O wait flag cleared, the increased pstate will be restored
+ to previous state.
+
+
``cpupower`` tool support for ``amd-pstate``
===============================================
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 | 38 +++++++++++++++++++++ 1 file changed, 38 insertions(+)