linux-kernel - [PATCH v7 02/13] Documentation: amd-pstate: add EPP profiles introduction

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Message-ID: <20221208111852.386731-3-perry.yuan@amd.com>
Date:   Thu, 8 Dec 2022 19:18:41 +0800
From:   Perry Yuan <perry.yuan@....com>
To:     <rafael.j.wysocki@...el.com>, <Mario.Limonciello@....com>,
        <ray.huang@....com>, <viresh.kumar@...aro.org>
CC:     <Deepak.Sharma@....com>, <Nathan.Fontenot@....com>,
        <Alexander.Deucher@....com>, <Shimmer.Huang@....com>,
        <Xiaojian.Du@....com>, <Li.Meng@....com>, <wyes.karny@....com>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v7 02/13] Documentation: amd-pstate: add EPP profiles introduction

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

The patch add AMD pstate EPP feature introduction and what EPP
preference supported for AMD processors.

User can get supported list from
energy_performance_available_preferences attribute file, or update
current profile to energy_performance_preference file

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"

Signed-off-by: Perry Yuan <Perry.Yuan@....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