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Thu, 28 May 2026 12:39:48 -0700 Date: Thu, 28 May 2026 12:39:46 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: , Will Deacon , Joerg Roedel , Robin Murphy , Jason Gunthorpe , Mostafa Saleh , Daniel Mentz , Ashish Mhetre , Subject: Re: [PATCH v7 08/11] iommu/arm-smmu-v3: Implement pm_runtime & system sleep ops Message-ID: References: <20260527221407.1756491-1-praan@google.com> <20260527221407.1756491-9-praan@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260527221407.1756491-9-praan@google.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000C6187:EE_|PH7PR12MB9176:EE_ X-MS-Office365-Filtering-Correlation-Id: 2cf89bd6-3ebd-4590-1fb2-08debcf0efb8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|1800799024|82310400026|376014|4143699003|11063799006|18002099003|22082099003|56012099006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: dBFzWC5/kXKYTeA59ZxtXfqy/ayCexBUjbBBEoFxcUszFni8WgIM2nv0Ouexqzo7veFRn1xfo/DgPlRkYOgsrVbrK/jE6R7O2GHfwHKDYJQei/2RsGVI4rW4BF1aE4ljSWw3cg7yjkmy4QJ8/j3bzQHyilgVrojrpsZig2WhfJSS6h8+X3RCLkSppNJIwY3WQrJ+GNT++Ujg3b0Ny34LbQeDlTqT0ZC818gu1BaxovT44HHw6AW4oqkP29dTBzBjdwFJqybPt5MO3HrbOHULIyU2Nj7Ag+G7k+a/ZZwji9krRRPJaL6M5TnbSUEQVrsRQYiJSy4J4Zb2BikiwBzbhT6jQSuDXrj4dGZXyWkFnD0bmzo9AEAuFM4R1QeHJuyxfSWwBLDKF6cEwp4TUCPAKQyWy+xBtRN3pVCFr+ZlEVangLlk0s9wLgDLHKcBQDMB X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 May 2026 19:40:13.2105 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2cf89bd6-3ebd-4590-1fb2-08debcf0efb8 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: MWH0EPF000C6187.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB9176 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260528_124023_418409_F4A2792C X-CRM114-Status: GOOD ( 18.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 27, 2026 at 10:14:04PM +0000, Pranjal Shrivastava wrote: > +/* Runtime PM helpers */ > +__maybe_unused static int arm_smmu_rpm_get(struct arm_smmu_device *smmu) > +{ > + int ret; > + > + if (pm_runtime_enabled(smmu->dev)) { > + ret = pm_runtime_resume_and_get(smmu->dev); > + if (ret < 0) { > + dev_err(smmu->dev, "failed to resume device: %d\n", ret); > + return ret; > + } > + } > + > + return 0; Nit: ret is used within the first if. Yet, I wouldn't like it to move. So, maybe do an early return: if (!pm_runtime_enabled(smmu->dev)) return 0; > +__maybe_unused static void arm_smmu_rpm_put(struct arm_smmu_device *smmu) > +{ > + int ret; > + > + if (pm_runtime_enabled(smmu->dev)) { > + ret = pm_runtime_put_autosuspend(smmu->dev); > + if (ret < 0) > + dev_err(smmu->dev, "failed to suspend device: %d\n", ret); > + } > +} Ditto > + > +static inline u32 arm_smmu_cmdq_owner_prod_idx(struct arm_smmu_cmdq *cmdq) > +{ > + return atomic_read(&cmdq->owner_prod) & CMDQ_PROD_IDX_MASK; > +} > + > static void parse_driver_options(struct arm_smmu_device *smmu) > { > int i = 0; > @@ -789,7 +822,8 @@ int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu, > /* b. Stop gathering work by clearing the owned flag */ > prod = atomic_fetch_andnot_relaxed(CMDQ_PROD_OWNED_FLAG, > &cmdq->q.llq.atomic.prod); > - prod &= ~CMDQ_PROD_OWNED_FLAG; > + /* Strip all metadata flags */ > + prod &= CMDQ_PROD_IDX_MASK; Should its prior atomic_fetch_andnot_relaxed() call do something about the CMDQ_PROD_STOP_FLAG as well? > +/* > + * Lockless pre-check to elide invalidations if SMMU is suspended. > + * Races with concurrent suspend are benign: the cmpxchg loop in > + * arm_smmu_cmdq_issue_cmdlist() acts as the true commit point. > + * If we lose the race, that loop observes Q_STOP == 1 and safely > + * drops the command. If we win, the suspend thread waits for us. > + */ > +static inline bool arm_smmu_can_elide(struct arm_smmu_device *smmu) > +{ > + return !!Q_STOP(READ_ONCE(smmu->cmdq.q.llq.prod)); > +} arm_smmu_cmdq_can_elide() Should it handle a secondary_cmdq? Nicolin