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Wysocki" , Viresh Kumar , Jonathan Corbet , Shuah Khan Cc: Mario Limonciello , Perry Yuan , linux-pm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260723201228.22584-1-kprateek.nayak@amd.com> <20260723201228.22584-7-kprateek.nayak@amd.com> From: Mario Limonciello In-Reply-To: <20260723201228.22584-7-kprateek.nayak@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: CH2PR11CA0008.namprd11.prod.outlook.com (2603:10b6:610:54::18) To PH8PR12MB6914.namprd12.prod.outlook.com (2603:10b6:510:1cb::21) Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR12MB6914:EE_|CH2PR12MB9495:EE_ X-MS-Office365-Filtering-Correlation-Id: 9d56efbc-893c-464b-3e42-08dee9b566d1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|23010399003|376014|3023799007|10067099003|4143699003|11063799006|56012099006|6133799003|22082099003|18002099003; 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This attribute is read-only. > +as well. ``dynamic`` designates that the EPP is modified dynamically > +by the platform profile and the power supply status. Although this is true, I think it's very likely going to be something we forget to update as we add more criteria. How about just saying "modified dynamically on kernel events"? > 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 +357,20 @@ 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 the system profile and the current power source 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 ``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`` > ======================================