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Documentation: amd-pstate: add EPP profiles introduction 

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"

Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Wyes Karny <wyes.karny@amd.com>
Tested-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Perry Yuan 2023-01-31 17:00:07 +08:00 committed by Rafael J. Wysocki
parent 7bc1fcd399
commit e22abc6bb9
1 changed files with 19 additions and 0 deletions
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Documentation/admin-guide/pm/amd-pstate.rst
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@ -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`.