[PATCH v10 02/12] Documentation: amd-pstate: add EPP profiles introduction

Perry Yuan
2023-01-06T06:15:07Z

From: Perry Yuan <Perry.Yuan@amd.com>

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"

Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.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`.

--
2.34.1