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Wed, 2 Sep 2026 10:22:32 -0700 Date: Wed, 2 Sep 2026 10:22:31 -0700 From: Nicolin Chen To: "Kiryl Shutsemau (Meta)" CC: Will Deacon , Robin Murphy , "Joerg Roedel" , Jason Gunthorpe , "Pranjal Shrivastava" , Mostafa Saleh , "Thierry Reding" , Krishna Reddy , Jonathan Hunter , Breno Leitao , Kyle McMartin , Usama Arif , , , , , Subject: Re: [PATCH v4 1/2] iommu/arm-smmu-v3: Add a cmdq_entries module parameter Message-ID: References: <20260902121724.3494954-1-kas@kernel.org> <20260902121724.3494954-2-kas@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260902121724.3494954-2-kas@kernel.org> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ5PEPF00000207:EE_|PH7PR12MB5734:EE_ X-MS-Office365-Filtering-Correlation-Id: 034f4dab-9761-45c0-1d79-08df0916d3db X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700016|376014|7416014|1800799024|23010399003|10067099003|11063799006|56012099006|4143699003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: GkPNNp5OB1EPhbTepf38boXk/wuViPboC3/+NyN+slMYKmKjHsq6tDLo9wb0tbthPkYbevJZi2dH2FIni3cZY/izTg17BGAT5t1UwjphDKoxwnCYisR5T5F8y12ASdLX+5j6F+GN4QCBcuThYXGvquL0d+XI0WVKkMTMzA3lXaBNBDzg0jPzHxCTFYrTHuMe7OAOLViQUZGglkSzclUCKAyra1nr54frg5eql62YVJRoYAZn/Y5cCVhJp+tWCut4FNXY52fWxSpiZYZRDPBOQbdtlKWEIpYNxgHeBpSGheyD3Htdoa2oXgdA5rQ49NQDSlP0nxpBuDQA2ogk9+ZzXuxfe1ifwZ/yFyqYxQmNvDnP1OyudyMYAmh9mmAWH3VCjuOj7V9lsbPNUPWBwZX1/dnHA4H3CItymNsbaMkk7SAtaex4+JJknFZTeFwbN0HG X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Sep 2026 17:22:55.7882 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 034f4dab-9761-45c0-1d79-08df0916d3db X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.160];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SJ5PEPF00000207.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB5734 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260902_102303_023381_F1C15AC8 X-CRM114-Status: GOOD ( 12.73 ) 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, Sep 02, 2026 at 01:17:23PM +0100, Kiryl Shutsemau (Meta) wrote: > +/** > + * arm_smmu_queue_max_n_shift() - pick the log2 depth of a queue > + * @hw_shift: log2 depth the hardware allows, capped for natural alignment > + * @ent_sz_shift: log2 of the queue entry size in bytes > + * @want: number of entries asked for, or zero to use @hw_shift > + * > + * @want is rounded down to a power of two. It never sizes a queue below one > + * page, because coherent DMA is page granular: a shallower queue occupies the > + * same memory as one that fills the page, and arm_smmu_init_one_queue() stops > + * shrinking at a page too. Well, since we want the cmdq depth, why not name the parameter "max_cmdq_depth"? Then, no rounding and more straightforward. Nicolin