[PATCH v9 10/13] Documentation: amd-pstate: add amd pstate driver mode introduction

[Perry Yuan]

From: Perry Yuan <Perry.Yuan@xxxxxxx>

The amd-pstate driver has two operation modes supported:
* CPPC Autonomous (active) mode
* CPPC non-autonomous (passive) mode.
active mode and passive mode can be chosen by different kernel parameters.

Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
---
 Documentation/admin-guide/pm/amd-pstate.rst | 26 +++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index 33ab8ec8fc2f..62744dae3c5f 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -299,8 +299,30 @@ module which supports the new AMD P-States mechanism on most of the future AMD
 platforms. The AMD P-States mechanism is the more performance and energy
 efficiency frequency management method on AMD processors.
 
-Kernel Module Options for ``amd-pstate``
-=========================================
+
+AMD Pstate Driver Operation Modes
+=================================
+
+``amd_pstate`` CPPC has two operation modes: CPPC Autonomous(active) mode and
+CPPC non-autonomous(passive) mode.
+active mode and passive mode can be chosen by different kernel parameters.
+When in Autonomous mode, CPPC ignores requests done in the Desired Performance
+Target register and takes into account only the values set to the Minimum requested
+performance, Maximum requested performance, and Energy Performance Preference
+registers. When Autonomous is disabled, it only considers the Desired Performance Target.
+
+Active Mode
+------------
+
+``amd_pstate=active``
+
+This is the low-level firmware control mode which is implemented by ``amd_pstate_epp``
+driver with ``amd_pstate=active`` passed to the kernel in the command line.
+In this mode, ``amd_pstate_epp`` driver provides a hint to the hardware if software
+wants to bias toward performance (0x0) or energy efficiency (0xff) to the CPPC firmware.
+then CPPC power algorithm will calculate the runtime workload and adjust the realtime
+cores frequency according to the power supply and thermal, core voltage and some other
+hardware conditions.
 
 Passive Mode
 ------------
-- 
2.34.1