linux-kernel - Re: [PATCH v8 10/13] Documentation: amd-pstate: add amd pstate driver mode introduction

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Date:   Mon, 19 Dec 2022 17:28:11 -0600
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.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
Subject: Re: [PATCH v8 10/13] Documentation: amd-pstate: add amd pstate driver
 mode introduction

On 12/19/2022 00:40, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
> 
> Introduce ``amd-pstate`` CPPC has two operation modes:

Drop the word Introduce.

> * CPPC Autonomous (active) mode
> * CPPC non-autonomous (passive) mode.
> active mode and passive mode can be chosen by different kernel parameters.
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>

With nit fixed:

Reviewed-by: Mario Limonciello <mario.limonciello@....com>

> ---
>   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
>   ------------