Documentation: add amd-pstate kernel command line options

Add a new amd pstate driver command line option to enable driver passive
working mode via MSR and shared memory interface to request desired
performance within abstract scale and the power management firmware
(SMU) convert the perf requests into actual hardware pstates.

Also the `disable` parameter can disable the pstate driver loading by
adding `amd_pstate=disable` to kernel command line.

Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Tested-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a465d52..42af9ca 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6959,3 +6959,14 @@
                                memory, and other data can't be written using
                                xmon commands.
                        off     xmon is disabled.
+
+       amd_pstate=     [X86]
+                       disable
+                         Do not enable amd_pstate as the default
+                         scaling driver for the supported processors
+                       passive
+                         Use amd_pstate as a scaling driver, driver requests a
+                         desired performance on this abstract scale and the power
+                         management firmware translates the requests into actual
+                         hardware states (core frequency, data fabric and memory
+                         clocks etc.)