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Message-ID: <20221107175705.2207842-3-Perry.Yuan@amd.com>
Date: Tue, 8 Nov 2022 01:56:59 +0800
From: Perry Yuan <Perry.Yuan@....com>
To: <rafael.j.wysocki@...el.com>, <ray.huang@....com>,
<viresh.kumar@...aro.org>
CC: <Deepak.Sharma@....com>, <Mario.Limonciello@....com>,
<Nathan.Fontenot@....com>, <Alexander.Deucher@....com>,
<Shimmer.Huang@....com>, <Xiaojian.Du@....com>, <Li.Meng@....com>,
<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
Perry Yuan <Perry.Yuan@....com>
Subject: [PATCH v3 2/8] Documentation: amd-pstate: add EPP profiles introduction
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 8f3d30c5a0d8..78c6525d5a49 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``
+
+All the supported EPP preference could be selected, List of the strings that
+can be set to the ``energy_performance_preference`` attribute
+those different profiles represent different energy vs efficiency hints provided
+to low-level firmware
+however, the ``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
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