Re: [PATCH v2 6/9] Documentation/amd-pstate: Update dynamic_epp documentation with new behavior

[Mario Limonciello <mario.limonciello@amd.com>]

On 7/23/26 15:12, K Prateek Nayak wrote:
> Update the admin-guide for dynamic_epp describing the latest integration
> into energy_performance_preference selections.
> 
> Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
> ---
> Changelog rfc v1..v2:
> 
> o Updated documentation based on current state of rework.
> ---
>   Documentation/admin-guide/pm/amd-pstate.rst | 46 ++++++++++-----------
>   1 file changed, 23 insertions(+), 23 deletions(-)
> 
> diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
> index a95e2ebce005..b0f1626bd783 100644
> --- a/Documentation/admin-guide/pm/amd-pstate.rst
> +++ b/Documentation/admin-guide/pm/amd-pstate.rst
> @@ -317,7 +317,10 @@ 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. ``custom`` designates that integer values 0-255 may be written
> -as well.  This attribute is read-only.
> +as well. ``dynamic`` designates that the EPP is modified dynamically
> +by the platform profile and the power supply status. 

Although this is true, I think it's very likely going to be something we 
forget to update as we add more criteria.  How about just saying 
"modified dynamically on kernel events"?

> See ``Dynamic energy
> +performance profile`` section below to know more about the ``dynamic``
> +mode. This attribute is read-only.
>   
>   ``energy_performance_preference``
>   
> @@ -326,13 +329,11 @@ and user can change current preference according to energy or performance needs
>   Coarse named profiles are available in the attribute
>   ``energy_performance_available_preferences``.
>   Users can also write individual integer values between 0 to 255.
> -When dynamic EPP is enabled, writes to energy_performance_preference are blocked
> -even when EPP feature is enabled by platform firmware. Lower epp values shift the bias
> -towards improved performance while a higher epp value shifts the bias towards
> -power-savings. The exact impact can change from one platform to the other.
> -If a valid integer was last written, then a number will be returned on future reads.
> -If a valid string was last written then a string will be returned on future reads.
> -This attribute is read-write.
> +Lower epp values shift the bias towards improved performance while a higher epp
> +value shifts the bias towards power-savings. The exact impact can change from
> +one platform to the other. If a valid integer was last written, then a number
> +will be returned on future reads. If a valid string was last written then a
> +string will be returned on future reads. This attribute is read-write.
>   
>   ``boost``
>   The `boost` sysfs attribute provides control over the CPU core
> @@ -356,21 +357,20 @@ Other performance and frequency values can be read back from
>   Dynamic energy performance profile
>   ==================================
>   The amd-pstate driver supports dynamically selecting the energy performance
> -profile based on whether the machine is running on AC or DC power.
> -
> -Whether this behavior is enabled by default depends on the kernel command line option
> -``amd_dynamic_epp`` is set. This behavior can also be overridden
> -at runtime by the sysfs file ``/sys/devices/system/cpu/amd_pstate/dynamic_epp``.
> -
> -When set to enabled, the driver will select a different energy performance
> -profile when the machine is running on battery or AC power. The driver will
> -also register with the platform profile handler to receive notifications of
> -user desired power state and react to those.
> -When set to disabled, the driver will not change the energy performance profile
> -based on the power source and will not react to user desired power state.
> -
> -Attempting to manually write to the ``energy_performance_preference`` sysfs
> -file will fail when ``dynamic_epp`` is enabled.
> +profile based on the system profile and the current power source in active mode.
> +
> +The ``dynamic`` mode is listed in
> +``/sys/devices/system/cpu/cpuX/cpufreq/energy_performance_available_preferences``
> +when available while running under the ``powersave`` governor. The ``dynamic``
> +mode can be toggled on by writing the same to the sysfs file
> +``/sys/devices/system/cpu/cpuX/cpufreq/energy_performance_preference`` when
> +available.
> +
> +When ``energy_performance_preference`` is set to ``dynamic``, the driver will
> +select a different energy performance profile when the machine is running on
> +battery or AC power. The driver will also register with the platform profile
> +handler to receive notifications of user desired power state and react to
> +those.
>   
>   ``amd-pstate`` vs ``acpi-cpufreq``
>   ======================================