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Thu, 6 Aug 2026 13:09:50 -0700 From: Sumit Gupta To: , , , , , , , , , , , , , , , , , CC: , , , , , , , Subject: [PATCH v4 4/4] cpufreq: CPPC: Preserve OSPM-set registers across suspend/resume Date: Fri, 7 Aug 2026 01:38:57 +0530 Message-ID: <20260806200857.601152-5-sumitg@nvidia.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260806200857.601152-1-sumitg@nvidia.com> References: <20260806200857.601152-1-sumitg@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-NVConfidentiality: public Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF000026C9:EE_|MW4PR12MB7430:EE_ X-MS-Office365-Filtering-Correlation-Id: eeb6ef59-b27d-465c-0812-08def3f6bb8c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700016|7416014|376014|23010399003|18002099003|22082099003|56012099006|11063799006|10067099003|921020; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: rlfTtxgwlgaktdx5N4X16tYnYszZyBlvjk3HzHH1apEB/th1W9rfoiWolZFf+ramgi3Y3riKRFt6Elec5NhHU8vVYeXwN4kEAU3rVZrq4c8qymYLftBCm3gbXTUs6/HaF8suRnPp91j6QNuRcVIKFglswr8OAbS03wIlfCRLh1j408TgQedx8UWYTxZPk0CIcTlJYwdXd8SsLE/RvSBBk92m5JU9ss5h9nFEMJpr3TfJJ8di9zbF0k/Np/7XaHD0Mm98/1yimUsDhHHHuTVLosA4pHFRYUQLM+Hhe8jEuXE98ngd0hWzzVtvFJ4aJ25cYGuFjuI6r23icy0rhOT4KXH+Jq8sQ9ZH99VZOQGfkQ51zeezswavQO3rrNwfukMZoK8nCl9XTE29SSipLBg+AukQzBLYE1hJeqdTgdq05n0ajr78yxfhuQFycTrHeREl X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2026 20:10:16.6832 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: eeb6ef59-b27d-465c-0812-08def3f6bb8c X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF000026C9.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB7430 The driver preserves the OSPM-set registers across CPU hotplug, but system suspend/resume is a separate path. On platforms that reset those registers or the performance controls across suspend, the values are lost. Reuse the same save/restore mechanism for suspend/resume: - suspend() saves the current OSPM-set values, restores the firmware values and sets a per-policy flag. It runs before devices are suspended and before the secondary CPUs go offline, while CPPC access is still safe. It also covers a policy whose CPUs stay online, for which offline() never runs. - offline() sees the flag and leaves those register accesses alone, parking only the performance request. - resume() needs the same steps as online(). The core has already run online() for a policy whose CPUs were offlined and brought back. So, resume() calls it only for a policy that still has the flag set. - online() clears the flag, so that a later offline() takes a fresh snapshot. Suggested-by: Christian Loehle Signed-off-by: Sumit Gupta --- drivers/cpufreq/cppc_cpufreq.c | 54 ++++++++++++++++++++++++++++++++-- 1 file changed, 51 insertions(+), 3 deletions(-) diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index f8628b1fc6b7..32f38b0c492b 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -87,6 +87,12 @@ struct cppc_saved_vals { struct cppc_policy_state { struct cppc_saved_vals regs[CPPC_NR_SAVED_REGS]; + /* + * Set by suspend() after it saves the OSPM-set values and restores the + * firmware ones, so a later offline() does not repeat those accesses. + * Cleared at init() and by online(). + */ + bool suspend_regs_handled; }; static DEFINE_PER_CPU(struct cppc_policy_state, cppc_policy_state); @@ -125,6 +131,9 @@ static void cppc_cpufreq_save_regs(struct cpufreq_policy *policy, u64 val; int i; + if (saved_type == CPPC_SAVED_FIRMWARE) + st->suspend_regs_handled = false; + for (i = 0; i < CPPC_NR_SAVED_REGS; i++) { if (cppc_saved_regs[i].get(cpu, &val)) val = U64_MAX; @@ -952,9 +961,14 @@ static int cppc_cpufreq_cpu_offline(struct cpufreq_policy *policy) unsigned int cpu = policy->cpu; int ret; - /* Leave the platform in its pre-driver state while offline. */ - cppc_cpufreq_save_regs(policy, CPPC_SAVED_REQUESTED); - cppc_cpufreq_apply_saved_regs(policy, CPPC_SAVED_FIRMWARE); + /* + * Leave the platform in its pre-driver state while offline, unless + * suspend() already did so earlier in this suspend cycle. + */ + if (!cppc_cpufreq_policy_state(policy)->suspend_regs_handled) { + cppc_cpufreq_save_regs(policy, CPPC_SAVED_REQUESTED); + cppc_cpufreq_apply_saved_regs(policy, CPPC_SAVED_FIRMWARE); + } /* * Request the lowest desired performance while the policy has no online @@ -1014,6 +1028,8 @@ static int cppc_cpufreq_cpu_online(struct cpufreq_policy *policy) unsigned int cpu = policy->cpu; int ret; + cppc_cpufreq_policy_state(policy)->suspend_regs_handled = false; + cppc_cpufreq_cpu_fie_resync(policy); ret = cppc_set_enable(cpu, true); @@ -1050,6 +1066,36 @@ static int cppc_cpufreq_cpu_online(struct cpufreq_policy *policy) return 0; } +/* + * Save the OSPM-set values and restore the firmware values here, while CPPC + * access is still safe. Secondary CPUs go offline much later, with devices + * already suspended, so offline() is too late for these accesses and leaves + * them alone until resume. Doing it here covers every policy, including one + * whose CPUs stay online, for which offline() never runs. + */ +static int cppc_cpufreq_cpu_suspend(struct cpufreq_policy *policy) +{ + cppc_cpufreq_save_regs(policy, CPPC_SAVED_REQUESTED); + cppc_cpufreq_apply_saved_regs(policy, CPPC_SAVED_FIRMWARE); + cppc_cpufreq_policy_state(policy)->suspend_regs_handled = true; + + return 0; +} + +/* + * CPUs offlined during suspend come back before the core calls resume(), so + * online() has already run for their policies and cleared the flag. It remains + * set only for a policy whose CPUs stayed online, and only that policy needs + * online() here. + */ +static int cppc_cpufreq_cpu_resume(struct cpufreq_policy *policy) +{ + if (!cppc_cpufreq_policy_state(policy)->suspend_regs_handled) + return 0; + + return cppc_cpufreq_cpu_online(policy); +} + static void cppc_cpufreq_cpu_exit(struct cpufreq_policy *policy) { struct cppc_cpudata *cpu_data = policy->driver_data; @@ -1364,6 +1410,8 @@ static struct cpufreq_driver cppc_cpufreq_driver = { .exit = cppc_cpufreq_cpu_exit, .online = cppc_cpufreq_cpu_online, .offline = cppc_cpufreq_cpu_offline, + .suspend = cppc_cpufreq_cpu_suspend, + .resume = cppc_cpufreq_cpu_resume, .set_boost = cppc_cpufreq_set_boost, .attr = cppc_cpufreq_attr, .name = "cppc_cpufreq", -- 2.34.1