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Wysocki" , Viresh Kumar , Huang Rui , Jonathan Corbet , Shuah Khan CC: Perry Yuan , K Prateek Nayak , , , Subject: [RFC PATCH 4/6] Documentation/amd-pstate: Update dynamic_epp documentation with new behavior Date: Tue, 30 Jun 2026 19:03:02 +0000 Message-ID: <20260630190304.5671-1-kprateek.nayak@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260630185904.5602-1-kprateek.nayak@amd.com> References: <20260630185904.5602-1-kprateek.nayak@amd.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF0001AB57:EE_|DS4PR12MB9708:EE_ X-MS-Office365-Filtering-Correlation-Id: ca3fdb41-4104-48cb-2dda-08ded6da4060 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|36860700016|376014|82310400026|1800799024|6133799003|3023799007|11063799006|22082099003|56012099006|18002099003; X-Microsoft-Antispam-Message-Info: i8yA31x9wk9P5gIEJdC0kgqfsO1f4mwRO9gVNRh1u+0uI02pArCDEYR5rgmKoSxfboDYs1F0g/V6OhXSehvSXHZlSX7MTFD9IZBTM2CwHhbg17VKaLpbGmJ2kbOZJH1Eed/e7BSoyTBoBBBY0j5Z6LBD+dBQ55PGUVKHCxjLMtstMsLnZtJmBQuDKTr2h8RnAG0ciO1KB3tG229mHrK9qhQj9kJ9b+Pxu/vdWjIIdXI0//RnfVC1X2CoHjdGf5OKU6IyEZxOVexoPj0MXsMz8F/VvJnaxDcsti32N1zeHeG3fWds/EFIvtHfQ+G+2YQ/cJ5HMfJaut1RK/xImZISyseessV4dyh8sKw1fjM1zs2vrQjPN3PD5ImqBKmAjEh11PWbUqwGqXnCP7mdSKW+0TXXH88NNMZQ08swQ+yl3wTT7MO1vymkwC7lIFPSmbRxete8Jzk5Cu3OHAwoyHvMMN9AVPcL06DPDgeI/Ywmlw9nN/JtXbsbcr8nDxxbOxZxdC7DGPm2pM4s5b9Ja+ehN6za5OTlc+JVNxeWULovZh1JjkV55Nc3MahYswu7h2PwlPrm3xtGBBPF0wJurLVmwAf0vnu+2M+2ypOe1dJUHObaqAo6pSu5SUSHw64b1S5u0++z32rjnt30/6TbEXinA1XZTtTvmRgUA6vT8GG081fYFhbeoXUt6GjM2Sl/PcoWF4mBKFQCy4KcDqvnjjhxyg== X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(23010399003)(36860700016)(376014)(82310400026)(1800799024)(6133799003)(3023799007)(11063799006)(22082099003)(56012099006)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 6nB6Y6WytOUukj9I8inp8UixNinQHmj9tBZs6Sueeo0pKJ8fzPMtJjFtWOnpzNDBU65vmSaLGjTCCNDsHNMrc5OAVxB2mckcSDO4+AdBjrGoqI2SmOw8MTa9A3GSXq4Q/ajMPnmyIj7OxCZlTBLqIIw39eBPHoP5/Qwvfd+H01cGkmM3Xo4JM5HeH36hjeEyyNkBpbxQ3ftczm4L8Efuo1YnqVF5jfQX0dxXJc2As8Junk9JncLqJ27j7+N42X+4hbFvuomfda6UdarxLrbgzaeFhyBFRYgBSOpXnOADO/RogDpKS/OSlgdb09Mu9RGlI4Ipeqla4d8F5+c2JHi/vu1smKyPoTPaNUXbz03FsFIwpIF+wqPYO3lnA8kjummnAGUj3FOUVd5hj7QLtfc2iTOoTL3IpxSnk14jzJ8ZwdTCWYlGzYkkrPBKXmtnFKsT X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2026 19:03:20.4008 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ca3fdb41-4104-48cb-2dda-08ded6da4060 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF0001AB57.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS4PR12MB9708 Update the admin-guide for dynamic_epp describing the latest integration into energy_performance_preference selections. Signed-off-by: K Prateek Nayak --- Documentation/admin-guide/pm/amd-pstate.rst | 61 +++++++++++++-------- 1 file changed, 38 insertions(+), 23 deletions(-) diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index a95e2ebce005..1afc2f8b3f0e 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -317,7 +317,10 @@ 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. ``custom`` designates that integer values 0-255 may be written -as well. This attribute is read-only. +as well. ``dynamic`` designates that the EPP is modified dynamically +by the platform profile and the power supply status. See ``Dynamic energy +performance profile`` section below to know more about the ``dynamic`` +mode. This attribute is read-only. ``energy_performance_preference`` @@ -326,13 +329,11 @@ and user can change current preference according to energy or performance needs Coarse named profiles are available in the attribute ``energy_performance_available_preferences``. Users can also write individual integer values between 0 to 255. -When dynamic EPP is enabled, writes to energy_performance_preference are blocked -even when EPP feature is enabled by platform firmware. Lower epp values shift the bias -towards improved performance while a higher epp value shifts the bias towards -power-savings. The exact impact can change from one platform to the other. -If a valid integer was last written, then a number will be returned on future reads. -If a valid string was last written then a string will be returned on future reads. -This attribute is read-write. +Lower epp values shift the bias towards improved performance while a higher epp +value shifts the bias towards power-savings. The exact impact can change from +one platform to the other. If a valid integer was last written, then a number +will be returned on future reads. If a valid string was last written then a +string will be returned on future reads. This attribute is read-write. ``boost`` The `boost` sysfs attribute provides control over the CPU core @@ -356,21 +357,35 @@ Other performance and frequency values can be read back from 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 command line option -``amd_dynamic_epp`` is set. This behavior can also be overridden -at runtime by the sysfs file ``/sys/devices/system/cpu/amd_pstate/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. The driver will -also register with the platform profile handler to receive notifications of -user desired power state and react to those. -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. +profile based on whether the machine is running on AC or DC power in active +mode. + +The ``dynamic`` mode is listed in +``/sys/devices/system/cpu/cpuX/cpufreq/energy_performance_available_preferences`` +when available while running under the ``powersave`` governor. The ``dynamic`` +mode can be toggled on by writing the same to the sysfs file +``/sys/devices/system/cpu/cpuX/cpufreq/energy_performance_preference`` when +available. + +When ``amd_dynamic_epp=disable`` is added to the kernel command line, +``dynamic`` option is not available in +``energy_performance_available_preferences`` and the feature cannot be toggled +at runtime. + +When ``amd_dynamic_epp=enable`` is added to the kernel command line, ``dynamic`` +option is selected by default as ``energy_performance_preference`` when +amd-pstate-epp driver is loaded. + +The availability of ``dynamic`` option as an ``energy_performance_preference`` +can be found by inspecting the sysfs files +``/sys/devices/system/cpu/amd_pstate/dynamic_epp`` and +``/sys/devices/system/cpu/cpuX/cpufreq/energy_performance_available_preferences`` + +When ``energy_performance_preference`` is set to ``dynamic``, the driver will +select a different energy performance profile when the machine is running on +battery or AC power. The driver will also register with the platform profile +handler to receive notifications of user desired power state and react to +those. ``amd-pstate`` vs ``acpi-cpufreq`` ====================================== -- 2.34.1