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    Subject[PATCH v4 9/9] Documentation: amd-pstate: add amd pstate driver mode introduction
    Date
    Introduce ``amd-pstate`` CPPC has two operation modes:
    * CPPC Autonomous (active) mode
    * CPPC non-autonomous (passive) mode.
    active mode and passive mode can be choosed by whith different kernel parameters.

    Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
    ---
    Documentation/admin-guide/pm/amd-pstate.rst | 47 +++++++++++++++++++--
    1 file changed, 43 insertions(+), 4 deletions(-)

    diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
    index e7488891b12f..6ba02a658b31 100644
    --- a/Documentation/admin-guide/pm/amd-pstate.rst
    +++ b/Documentation/admin-guide/pm/amd-pstate.rst
    @@ -302,11 +302,11 @@ efficiency frequency management method on AMD processors.
    Kernel Module Options for ``amd-pstate``
    =========================================

    -.. _shared_mem:
    +.. legacy_cppc:

    -``shared_mem``
    -Use a module param (shared_mem) to enable related processors manually with
    -**amd_pstate.shared_mem=1**.
    +``legacy_cppc``
    +Use a module param (legacy_cppc) to enable related processors manually with
    +**amd_pstate=legacy_cppc**.
    Due to the performance issue on the processors with `Shared Memory Support
    <perf_cap_>`_, we disable it presently and will re-enable this by default
    once we address performance issue with this solution.
    @@ -321,6 +321,45 @@ If the CPU flags have ``cppc``, then this processor supports `Full MSR Support
    <perf_cap_>`_. Otherwise, it supports `Shared Memory Support <perf_cap_>`_.


    +AMD Pstae 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 choosed by whith 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-epp``
    +
    +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
    +------------
    +
    +``amd-pstate``
    +
    +It will be enabled if the ``amd_pstate=passive`` is passed to the kernel in the command line.
    +In this mode, ``amd-pstate``driver software specifies a desired QoS target in the CPPC
    +performance scale as a relative number. This can be expressed as percentage of nominal
    +performance (infrastructure max). Below the nominal sustained performance level,
    +desired performance expresses the average performance level of the processor subject
    +to the Performance Reduction Tolerance register. Above the nominal performance level,
    +processor must provide at least nominal performance requested and go higher if current
    +operating conditions allow.
    +
    +
    ``cpupower`` tool support for ``amd-pstate``
    ===============================================

    --
    2.34.1
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