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Shenoy" To: Dhananjay Ugwekar Cc: mario.limonciello@amd.com, perry.yuan@amd.com, ray.huang@amd.com, rafael@kernel.org, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] cpufreq/amd-pstate: Set the initial min_freq to lowest_nonlinear_freq Message-ID: References: <20241003083952.3186-1-Dhananjay.Ugwekar@amd.com> <20241003083952.3186-3-Dhananjay.Ugwekar@amd.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241003083952.3186-3-Dhananjay.Ugwekar@amd.com> X-ClientProxiedBy: SI2P153CA0021.APCP153.PROD.OUTLOOK.COM (2603:1096:4:190::20) To DS7PR12MB8252.namprd12.prod.outlook.com (2603:10b6:8:ee::7) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB8252:EE_|IA0PR12MB8375:EE_ X-MS-Office365-Filtering-Correlation-Id: 56de3d0a-409b-43ad-5b2a-08dce4513e2b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?kzofol3zc/Qz4xdT+c5ZMoYiqWm9bEjumqA9Lk5shhSnlWcJZiEr2FPY0XJ7?= =?us-ascii?Q?i51A2JGWjlymzSLaq5vwZtLcPzzYl5bkW4M93BBVpkg2xy18QplsEHhaindQ?= =?us-ascii?Q?vKq+ZKkolkrevoebA1BxTI+fNiPUCCJUpg1jZpVC8BeOqA6yHp4lDTVRLhAF?= =?us-ascii?Q?a/UAac1HOxgPDpMKfECNWeyT9WHXIsNxEZcp1v/PTOxqBbni53WuF95LQCQ3?= =?us-ascii?Q?Istavjwd2Lnw7E1n6Txstq5IBKotQ6M7mfLhG59TB6FO56byYgDkBRTAHoPd?= =?us-ascii?Q?hqzuKR8thWq6Uqr12IwfRPx/NwyqB/ILelE+WS4OruEzNtmmuUBPGt9sECft?= =?us-ascii?Q?Dld2piUoSpJhDFBoRfo6KxnjvM0DkG2Qw9c3xDamsAKMBSyw9xSeuEvLIEGC?= =?us-ascii?Q?vQSULkEK5WbqkUu44tmy563oWlSwos7j8uIRWbU9aXGCtexIXo9U9YMxVpTs?= =?us-ascii?Q?AGOVSGj8qgRC9nJg26rchyv4azOYcZ77r2Y3kgVx/vVO8UHjw3aH/Q30ctSN?= =?us-ascii?Q?a9asyqSyDOlpMEHj0Jfze1HlbuyLshjHONwovCBWobibbLcaS4Jv7XJtrF8m?= =?us-ascii?Q?4BV/J5mxoxaWYLgs2t3b6e+jrs0Yhk9J0drXtPk9Y7Un1Ky7U5g+k7a+92sz?= =?us-ascii?Q?8xV0GNwTWPM8kmAqANYnVQzDJJGoDWlj8fjcUpqwQexR2+oxpCYY3ZdpNltq?= =?us-ascii?Q?zSgmqinU7a1RTUEbLCAYbu1vw8R37qiaW1VCskkH2SvAv1NbooF7ootN4gyy?= =?us-ascii?Q?MnwcI50ddk1aJ8Vmc2g/W4qg01zy9DjAA3kozcO3+E9+taJz+oVww4qXAhL9?= =?us-ascii?Q?cKDHAJLqBlIDXof8Dnlrr88B1jQUU7AoKu30y/0SnWGDpsF7HKPmI8dvTZRk?= =?us-ascii?Q?oAzy4xvQZeYyT4j/MjdaQ85iDqsMxU02/mNEKzxpik3/XdTVTme4sH5dy8q0?= =?us-ascii?Q?gENEImOyJML1xVzQy13hm6GEx1DZQchDMMDWsLQFLj8O1Cjola9WRS4kIiOq?= =?us-ascii?Q?JLc+qj/VmWgqK40bO4XJfTYdFzFupxXpg6IxvRGyWmA37Ee+/V5yJPwINlbf?= =?us-ascii?Q?3C003gk7Mbe2RYEU+JY5XuUHehpVHIUPwp5IIrTa505V1B7x2/kGYrbD9DDO?= =?us-ascii?Q?BM2nGwayYEX+5L5OyP2b5PNRPXSEP/3fu+MbT2GAiZ4+K+jWHeZwYmaaTnfe?= =?us-ascii?Q?1Rdb7E8us7caE/MpNiJiKL7pqsC9Yxn+77yqvTKpCYNWMRMwNrqyNi74Z04x?= =?us-ascii?Q?qQEGLKI+xgsBVn2+Mv/XVPeiB1uMu5Bx6ddKzyW22ldY5kohLDehqqu8gn8e?= =?us-ascii?Q?f0WLfsRNeCcylEYVmZNpgJIbrKQ6QdagKCW16xY7rbFPDdKgtESCkAkD2nMz?= =?us-ascii?Q?i/yYo9UmbFHtX0e/UZbAB6KiFQZQCyAGTl626yVfvcyTcGcuseOp9ZZG8JJq?= =?us-ascii?Q?KGuegEYxwzaNkbD8dzvNzKqPofuZFwGYRer/pcFi5sBFoMka8haTtncO/gfv?= =?us-ascii?Q?Tdo1QXmRyQGwNs9NkBR4fnvQmVoeQIT3H8sWz31yT5nFM2QOniM4ZOIHvGVQ?= =?us-ascii?Q?ZJinfGRs0so8QxEIGdPlDi3nF1pxWK6Cu1osuzVF?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 56de3d0a-409b-43ad-5b2a-08dce4513e2b X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB8252.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Oct 2024 08:47:56.9547 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: yqa/6Do3K60dR8QLv00XHDITsaxL2cZ1JSAjmxc6ny5GNz2g7JI+GDQ7iGzw547IuCezfbfFwvie8/zJdY0rKA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8375 On Thu, Oct 03, 2024 at 08:39:54AM +0000, Dhananjay Ugwekar wrote: > According to the AMD architectural programmer's manual volume 2 [1], in > section "17.6.4.1 CPPC_CAPABILITY_1" lowest_nonlinear_perf is described > as "Reports the most energy efficient performance level (in terms of > performance per watt). Above this threshold, lower performance levels > generally result in increased energy efficiency. Reducing performance > below this threshold does not result in total energy savings for a given > computation, although it reduces instantaneous power consumption". So > lowest_nonlinear_perf is the most power efficient performance level, and > going below that would lead to a worse performance/watt. > > Also, setting the minimum frequency to lowest_nonlinear_freq (instead of > lowest_freq) allows the CPU to idle at a higher frequency which leads > to more time being spent in a deeper idle state (as trivial idle tasks > are completed sooner). This has shown a power benefit in some systems, > in other systems, power consumption has increased but so has the > throughput/watt. > > Use the get_init_min_freq() callback to set the initial lower limit for > amd-pstate driver to lowest_nonlinear_freq instead of lowest_freq. > > Link: https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf [1] It is good enough to quote "AMD64 Architecture Programmer's Manual, Volume 2, Revision 3.42" instead of providing a link. Other than that, Reviewed-by: Gautham R. Shenoy > > Signed-off-by: Dhananjay Ugwekar -- Thanks and Regards gautham. > --- > drivers/cpufreq/amd-pstate.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c > index b7a17a3ef122..f8abae9a0156 100644 > --- a/drivers/cpufreq/amd-pstate.c > +++ b/drivers/cpufreq/amd-pstate.c > @@ -995,13 +995,6 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy) > if (cpu_feature_enabled(X86_FEATURE_CPPC)) > policy->fast_switch_possible = true; > > - ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0], > - FREQ_QOS_MIN, policy->cpuinfo.min_freq); > - if (ret < 0) { > - dev_err(dev, "Failed to add min-freq constraint (%d)\n", ret); > - goto free_cpudata1; > - } > - > ret = freq_qos_add_request(&policy->constraints, &cpudata->req[1], > FREQ_QOS_MAX, policy->cpuinfo.max_freq); > if (ret < 0) { > @@ -1706,6 +1699,13 @@ static int amd_pstate_epp_resume(struct cpufreq_policy *policy) > return 0; > } > > +static int amd_pstate_get_init_min_freq(struct cpufreq_policy *policy) > +{ > + struct amd_cpudata *cpudata = policy->driver_data; > + > + return READ_ONCE(cpudata->lowest_nonlinear_freq); > +} > + > static struct cpufreq_driver amd_pstate_driver = { > .flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS, > .verify = amd_pstate_verify, > @@ -1719,6 +1719,7 @@ static struct cpufreq_driver amd_pstate_driver = { > .update_limits = amd_pstate_update_limits, > .name = "amd-pstate", > .attr = amd_pstate_attr, > + .get_init_min_freq = amd_pstate_get_init_min_freq, > }; > > static struct cpufreq_driver amd_pstate_epp_driver = { > @@ -1735,6 +1736,7 @@ static struct cpufreq_driver amd_pstate_epp_driver = { > .set_boost = amd_pstate_set_boost, > .name = "amd-pstate-epp", > .attr = amd_pstate_epp_attr, > + .get_init_min_freq = amd_pstate_get_init_min_freq, > }; > > static int __init amd_pstate_set_driver(int mode_idx) > -- > 2.34.1 >