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Wed, 17 May 2023 16:30:35 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by BN8NAM11FT075.mail.protection.outlook.com (10.13.176.208) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.6411.18 via Frontend Transport; Wed, 17 May 2023 16:30:35 +0000 Received: from beas.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Wed, 17 May 2023 11:30:32 -0500 From: Wyes Karny To: , , CC: , , , Wyes Karny Subject: [PATCH v4 3/3] cpufreq: Return failure if fast_switch is not set and fast_switch_possible is set Date: Wed, 17 May 2023 16:28:17 +0000 Message-ID: <20230517162817.8538-4-wyes.karny@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230517162817.8538-1-wyes.karny@amd.com> References: <20230517162817.8538-1-wyes.karny@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN8NAM11FT075:EE_|DS0PR12MB6535:EE_ X-MS-Office365-Filtering-Correlation-Id: 2ababee1-a5d9-463b-6690-08db56f40acf X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 May 2023 16:30:35.5961 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2ababee1-a5d9-463b-6690-08db56f40acf 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT075.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB6535 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org If fast_switch_possible flag is set by the scaling driver, the governor is free to select fast_switch function even if adjust_perf is set. Some scaling drivers which use adjust_perf don't set fast_switch thinking that the governor would never fall back to fast_switch. But the governor can fall back to fast_switch even in runtime if frequency invariance is disabled due to some reason. This could crash the kernel if the driver didn't set the fast_switch function pointer. Therefore, return failure in cpufreq_online function if fast_switch is not set and fast_switch_possible is set. Signed-off-by: Wyes Karny --- drivers/cpufreq/cpufreq.c | 5 +++++ include/linux/cpufreq.h | 4 +++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 6b52ebe5a890..7835ba4fa34c 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1376,6 +1376,11 @@ static int cpufreq_online(unsigned int cpu) goto out_free_policy; } + if (policy->fast_switch_possible && !cpufreq_driver->fast_switch) { + pr_err("fast_switch_possible is enabled but fast_switch callback is not set\n"); + ret = -EINVAL; + goto out_destroy_policy; + } /* * The initialization has succeeded and the policy is online. * If there is a problem with its frequency table, take it diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 26e2eb399484..8cdf77bb3bc1 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -340,7 +340,9 @@ struct cpufreq_driver { /* * ->fast_switch() replacement for drivers that use an internal * representation of performance levels and can pass hints other than - * the target performance level to the hardware. + * the target performance level to the hardware. If driver is setting this, + * then it needs to set fast_switch also. Because in certain scenario scale + * invariance could be disabled and governor can switch back to fast_switch. */ void (*adjust_perf)(unsigned int cpu, unsigned long min_perf,