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([2600:6c56:7d00:582f::64e]) by smtp.googlemail.com with ESMTPSA id d75a77b69052e-494ae425388sm95564141cf.39.2025.05.22.01.50.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 May 2025 01:50:58 -0700 (PDT) Message-ID: <15871c67-0d18-430f-935e-261b2cda855b@gmail.com> Date: Thu, 22 May 2025 03:50:55 -0500 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] cpufreq, docs: (userspace governor) add that actual freq is >= scaling_setspeed To: Shashank Balaji , "Rafael J. Wysocki" , Viresh Kumar , Jonathan Corbet Cc: linux-pm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Shinya Takumi References: <20250522-userspace-governor-doc-v1-1-c8a038e39084@sony.com> Content-Language: en-US From: Russell Haley In-Reply-To: <20250522-userspace-governor-doc-v1-1-c8a038e39084@sony.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/22/25 3:05 AM, Shashank Balaji wrote: > The userspace governor does not have the CPUFREQ_GOV_STRICT_TARGET flag, which > means the requested frequency may not strictly be followed. This is true in the > case of the intel_pstate driver with HWP enabled. When programming the > HWP_REQUEST MSR, the min_perf is set to `scaling_setspeed`, and the max_perf > is set to the policy's max. So, the hardware is free to increase the frequency > beyond the requested frequency. > > This behaviour can be slightly surprising, given the current wording "allows > userspace to set the CPU frequency". Hence, document this. > In my opinion, the documentation is correct, and it is the implementation in intel_pstate that is wrong. If the user wanted two separate knobs that control the minimum and maximum frequencies, they could leave intel_pstate in "active" mode and change scaling_min_freq and scaling_max_freq. If the user asks for the frequency to be set from userspace, the frequency had damn well better be set from userspace. - Russell