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Date: Fri, 11 Nov 2022 01:58:47 +0800 From: Perry Yuan <Perry.Yuan@....com> To: <rafael.j.wysocki@...el.com>, <Mario.Limonciello@....com>, <ray.huang@....com>, <viresh.kumar@...aro.org> CC: <Deepak.Sharma@....com>, <Nathan.Fontenot@....com>, <Alexander.Deucher@....com>, <Shimmer.Huang@....com>, <Xiaojian.Du@....com>, <Li.Meng@....com>, <wyes.karny@....com>, <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Perry Yuan <Perry.Yuan@....com> Subject: [PATCH v4 9/9] Documentation: amd-pstate: add amd pstate driver mode introduction 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@....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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