RE: [PATCH v4 9/9] Documentation: amd-pstate: add amd pstate driver mode introduction

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Mario 

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Tuesday, November 15, 2022 6:29 AM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>; rafael.j.wysocki@xxxxxxxxx; Huang,
> Ray <Ray.Huang@xxxxxxx>; viresh.kumar@xxxxxxxxxx
> Cc: Sharma, Deepak <Deepak.Sharma@xxxxxxx>; Fontenot, Nathan
> <Nathan.Fontenot@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng,
> Li (Jassmine) <Li.Meng@xxxxxxx>; Karny, Wyes <Wyes.Karny@xxxxxxx>;
> linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v4 9/9] Documentation: amd-pstate: add amd pstate
> driver mode introduction
> 
> Please run this through a spell checker before v5.
> 
> On 11/10/2022 11:58, Perry Yuan wrote:
> > 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.
> 
> can be chosen by different kernel parameters

Forget to reply this, 
I have fixed the words typo in the  v6.
Thanks for your review. 
Perry. 

> 
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > ---
> >   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
> 
> Pstate
> 
> > +=================================
> > +
> > +``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.
> 
> 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-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``
> >   ===============================================
> >

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