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Wysocki (Intel)" , Christian Loehle Cc: viresh.kumar@linaro.org, pierre.gondois@arm.com, ionela.voinescu@arm.com, zhenglifeng1@huawei.com, zhanjie9@hisilicon.com, saket.dumbre@intel.com, ray.huang@amd.com, mario.limonciello@amd.com, perry.yuan@amd.com, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, acpica-devel@lists.linux.dev, linux-tegra@vger.kernel.org, treding@nvidia.com, jonathanh@nvidia.com, vsethi@nvidia.com, ksitaraman@nvidia.com, sanjayc@nvidia.com, mochs@nvidia.com, bbasu@nvidia.com References: <20260806200857.601152-1-sumitg@nvidia.com> <46d81167-1548-4b6a-b6cc-38542b2d093e@nvidia.com> <146a49c4-5b2a-41db-90fd-6dd2028d2d53@arm.com> Content-Language: en-US From: Sumit Gupta In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: PN4PR01CA0057.INDPRD01.PROD.OUTLOOK.COM (2603:1096:c01:274::16) To DM4PR12MB5246.namprd12.prod.outlook.com (2603:10b6:5:399::17) 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: DM4PR12MB5246:EE_|DS2PR12MB9710:EE_ X-MS-Office365-Filtering-Correlation-Id: bb640f6c-a0c3-4f6d-268d-08df03ac1ab4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|366016|376014|7416014|56012099006|10067099003|6133799003|5023799004|22082099003|18002099003|11063799006|4143699003; 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Wysocki (Intel) wrote: > External email: Use caution opening links or attachments > > > On Wed, Aug 26, 2026 at 11:07 AM Christian Loehle > wrote: >> On 8/25/26 22:20, Sumit Gupta wrote: >>> On 07/08/26 01:38, Sumit Gupta wrote: >>>> This series keeps the CPPC cpufreq policy alive across CPU hotplug and >>>> preserves the OSPM-set CPPC registers (Energy Performance Preference, >>>> Autonomous Activity Window, Autonomous Selection - set via sysfs). >>>> >>>> Without online()/offline() callbacks, the core tears a policy down when >>>> its last CPU goes offline and rebuilds it on the way back, re-reading the >>>> CPPC capabilities each time. The values written to these registers can >>>> be lost: >>>> >>>> - Across CPU hotplug or suspend/resume: the platform may reset them >>>> while the CPU is offline. >>>> - On driver unload: the driver-written value is left in the register >>>> instead of returning to its pre-driver state. >>>> >>>> Handle these with: >>>> >>>> - Patch 1: adds online()/offline() callbacks so the core keeps policy >>>> alive across CPU hotplug instead of tearing it down and rebuilding it. >>>> - Patch 2: makes the autonomous selection register helpers take a u64. >>>> - Patch 3: adds a table-driven mechanism that captures each register's >>>> firmware value at init(), restores it from offline(), and reapplies >>>> the OSPM-set value from online(). >>>> - Patch 4: extends the same save/restore to system suspend/resume. >>> Gentle reminder. >>> Could this be considered for queuing if nothing further needs addressing. >> FWIW both sashiko findings look legit to me, the feedback counters one I >> wouldn't consider that drastic, given that these counters are expected to >> have 'fuzzy' readings anyhow, the second one is worse (losing sysfs settings >> on cpu_online()) > I agree. > > Besides, as I said elsewhere, I want this series to go in before any > other pending changes related to CPPC: > > https://lore.kernel.org/linux-acpi/20260826063019.670240-1-christian.loehle@arm.com/ > > and I really would like to get some tags on it before it goes in. It > clearly is not ready for 7.3, but it may be applicable early for 7.4 > if people care to respond to it. > > Thanks! Thanks for pointing this out. I did not receive a Sashiko review email for this series, so I was unaware of the findings. I have found the web review now. I will go through both findings and address them in v5. Thanks, Sumit