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b=pcpFOjX2l94uuAfWz5g7jf9BF3SQnrKHGiIdH4YRdKsDcG3hgjfe/g4tYz/N39ac1YyoevETVc3eizDl1zyIpZM/Y0u/h2IChB+j0Bw+sSjX4dJ3m1skyZ58u66fbDoajrv6jUgiyffOvX/bxG8C3PhHClHyMxPpjwgFASp/Up8= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from MN0PR12MB6101.namprd12.prod.outlook.com (2603:10b6:208:3cb::10) by CH2PR12MB9460.namprd12.prod.outlook.com (2603:10b6:610:27f::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8356.16; Fri, 17 Jan 2025 14:30:46 +0000 Received: from MN0PR12MB6101.namprd12.prod.outlook.com ([fe80::37ee:a763:6d04:81ca]) by MN0PR12MB6101.namprd12.prod.outlook.com ([fe80::37ee:a763:6d04:81ca%4]) with mapi id 15.20.8356.010; Fri, 17 Jan 2025 14:30:46 +0000 Message-ID: <270a1cce-8afe-497a-b30b-56157d75a863@amd.com> Date: Fri, 17 Jan 2025 08:30:45 -0600 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 6/6] cpufreq: CPPC: Support for autonomous selection in cppc_cpufreq To: "zhenglifeng (A)" , Russell Haley , rafael@kernel.org, lenb@kernel.org, robert.moore@intel.com, viresh.kumar@linaro.org, gautham.shenoy@amd.com, ray.huang@amd.com, pierre.gondois@arm.com Cc: acpica-devel@lists.linux.dev, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linuxarm@huawei.com, jonathan.cameron@huawei.com, zhanjie9@hisilicon.com, lihuisong@huawei.com, hepeng68@huawei.com, fanghao11@huawei.com References: <20250113122104.3870673-1-zhenglifeng1@huawei.com> <20250113122104.3870673-7-zhenglifeng1@huawei.com> <21654032-a394-4da9-8ee9-d7cb9df8c855@gmail.com> <6909eef3-20aa-4341-9177-a42323a0d5c6@huawei.com> Content-Language: en-US From: Mario Limonciello In-Reply-To: <6909eef3-20aa-4341-9177-a42323a0d5c6@huawei.com> Content-Type: text/plain; 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This file >>> + represents a range of values from 0 (performance preference) to >>> + 0xFF (energy efficiency preference) that influences the rate of >>> + performance increase/decrease and the result of the hardware's >>> + energy efficiency and performance optimization policies. >>> + >>> + Writing to this file only has meaning when Autonomous Selection is >>> + enabled. >>> + >>> + This file only presents if the cppc-cpufreq driver is in use. >> >> In intel_pstate driver, there is file with near-identical semantics: >> >> /sys/devices/system/cpu/cpuX/cpufreq/energy_performance_preference >> >> It also accepts a few string arguments and converts them to integers. >> >> Perhaps the same name should be used, and the semantics made exactly >> identical, and then it could be documented as present for either >> cppc_cpufreq OR intel_pstate? >> >> I think would be more elegant if userspace tooling could Just Work with >> either driver. >> >> One might object that the frequency selection behavior that results from >> any particular value of the register itself might be different, but they >> are *already* different between Intel's P and E-cores in the same CPU >> package. (Ugh.) > > Yes, I should use the same name. Thanks. > > As for accepting string arguments and converting them to integers, I don't > think it is necessary. It'll be a litte confused if someone writes a raw > value and reads a string I think. I prefer to let users freely set this > value. > > In addition, there are many differences between the implementations of > energy_performance_preference in intel_pstate and cppc_cpufreq (and > amd-pstate...). It is really difficult to explain all this differences in > this document. So I'll leave it to be documented as present for > cppc_cpufreq only. At least the interface to userspace I think we should do the best we can to be the same between all the drivers if possible. For example; I've got a patch that I may bring up in a future kernel cycle that adds raw integer writes to amd-pstates energy_performance_profile to behave the same way intel-pstate does. > >> >> -- >> Thanks, >> Russell >> >> >> >