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| author | Mario Limonciello (AMD) <superm1@kernel.org> | 2026-03-29 15:38:07 -0500 |
|---|---|---|
| committer | Mario Limonciello (AMD) <superm1@kernel.org> | 2026-04-02 11:29:02 -0500 |
| commit | e30ca6dd5345c5b8ba05f346a8e81105352fe571 (patch) | |
| tree | 751cb69f5363db19492b53fad8e0991e76a4acc1 /Documentation | |
| parent | a362ae6e7e85bca4c870c37085d7793c4beec360 (diff) | |
cpufreq/amd-pstate: Add dynamic energy performance preference
Dynamic energy performance preference changes the EPP profile based on
whether the machine is running on AC or DC power.
A notification chain from the power supply core is used to adjust EPP
values on plug in or plug out events.
When enabled, the driver exposes a sysfs toggle for dynamic EPP, blocks
manual writes to energy_performance_preference while it "owns" the EPP
updates.
For non-server systems:
* the default EPP for AC mode is `performance`.
* the default EPP for DC mode is `balance_performance`.
For server systems dynamic EPP is mostly a no-op.
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/pm/amd-pstate.rst | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index b43675b7f739..bb1341763882 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -325,7 +325,7 @@ 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 +firmware, but if the dynamic EPP feature is enabled, driver will block writes. This attribute is read-write. ``boost`` @@ -347,6 +347,22 @@ boost or `1` to enable it, for the respective CPU using the sysfs path Other performance and frequency values can be read back from ``/sys/devices/system/cpu/cpuX/acpi_cppc/``, see :ref:`cppc_sysfs`. +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 +config option `CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP`. This behavior can also be overridden +at runtime by the sysfs file ``/sys/devices/system/cpu/cpufreq/policyX/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. +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. ``amd-pstate`` vs ``acpi-cpufreq`` ====================================== |