linux-kernel - Re: [PATCH v8 02/13] Documentation: amd-pstate: add EPP profiles introduction

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Message-ID: <26c77388-83cc-291c-4205-e1f6fc071875@amd.com>
Date:   Mon, 19 Dec 2022 16:37:40 -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 02/13] Documentation: amd-pstate: add EPP profiles
 introduction

On 12/19/2022 00:40, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@....com>
> 
> The patch add AMD pstate EPP feature introduction and what EPP
> preference supported for AMD processors.

Don't use "the patch" or "this patch" in the commit message.

I would propose something like this:

> 
> User can get supported list from
> energy_performance_available_preferences attribute file, or update
> current profile to energy_performance_preference file


The amd-pstate driver supports a feature called energy performance
preference (EPP). Add information to the documentation to explain
how users can interact with the sysfs files for this feature.

> 
> 1) See all EPP profiles
> $ sudo cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_available_preferences
> default performance balance_performance balance_power power
> 
> 2) Check current EPP profile
> $ sudo cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference
> performance
> 
> 3) Set new EPP profile
> $ sudo bash -c "echo power > /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference"
> 
> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
> ---
>   Documentation/admin-guide/pm/amd-pstate.rst | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
> 
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index 06e23538f79c..33ab8ec8fc2f 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -262,6 +262,25 @@ lowest non-linear performance in `AMD CPPC Performance Capability
>   <perf_cap_>`_.)
>   This attribute is read-only.
>   
> +``energy_performance_available_preferences``
> +
> +A list of all the supported EPP preferences that could be used for
> +``energy_performance_preference`` on this system.
> +These profiles represent different hints that are provided
> +to the low-level firmware about the user's desired energy vs efficiency
> +tradeoff.  ``default`` represents the epp value is set by platform
> +firmware. This attribute is read-only.
> +
> +``energy_performance_preference``
> +
> +The current energy performance preference can be read from this attribute.
> +and user can change current preference according to energy or performance needs
> +Please get all support profiles list from
> +``energy_performance_available_preferences`` attribute, all the profiles are
> +integer values defined between 0 to 255 when EPP feature is enabled by platform
> +firmware, if EPP feature is disabled, driver will ignore the written value
> +This attribute is read-write.
> +
>   Other performance and frequency values can be read back from
>   ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`.
>