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Signed-off-by: K Prateek Nayak --- 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. 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`` ====================================== -- 2.34.1