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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [Patch] driver: cpufreq: use refclk delta based loop instead of udelay Content-Language: en-US To: Jon Hunter , , , , , CC: , References: <20230901152046.25662-1-sumitg@nvidia.com> From: Sumit Gupta In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.231.35] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS3PEPF000099DD:EE_|DS0PR12MB8344:EE_ X-MS-Office365-Filtering-Correlation-Id: c32c6e00-c31d-4e4a-3023-08dbab0b7dd0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.160;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge1.nvidia.com;CAT:NONE;SFS:(13230031)(4636009)(346002)(396003)(136003)(39860400002)(376002)(1800799009)(451199024)(82310400011)(186009)(36840700001)(46966006)(40470700004)(31686004)(36756003)(40460700003)(40480700001)(7636003)(8676002)(53546011)(86362001)(5660300002)(41300700001)(4326008)(8936002)(426003)(336012)(26005)(16526019)(47076005)(6666004)(36860700001)(83380400001)(31696002)(107886003)(2616005)(82740400003)(54906003)(110136005)(356005)(966005)(478600001)(4744005)(2906002)(70586007)(16576012)(70206006)(316002)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Sep 2023 16:50:04.5436 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c32c6e00-c31d-4e4a-3023-08dbab0b7dd0 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: DS3PEPF000099DD.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB8344 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/09/23 21:28, Jon Hunter wrote: > > > On 01/09/2023 16:20, Sumit Gupta wrote: >> Use reference clock count based loop instead of "udelay()" for >> sampling of counters to improve the accuracy of re-generated CPU >> frequency. "udelay()" internally calls "WFE" which stops the >> counters and results in bigger delta between the last set freq >> and the re-generated value from counters. The counter sampling >> window used in loop is the minimum number of reference clock >> cycles which is known to give a stable value of CPU frequency. >> The change also helps to reduce the sampling window from "500us" >> to "<50us". >> >> Suggested-by: Antti Miettinen >> Signed-off-by: Sumit Gupta > > > Please can you correct the subject and drop the 'driver:'. > > Jon > Corrected subject and added another patch in v2 at [1]. [1] https://lore.kernel.org/lkml/20230901164113.29139-1-sumitg@nvidia.com/ Thank you, Sumit Gupta