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([2600:6c56:7d00:582f::64e]) by smtp.googlemail.com with ESMTPSA id 956f58d0204a3-649d447df2bsm423325d50.4.2026.02.02.17.36.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Feb 2026 17:36:17 -0800 (PST) Message-ID: <74f3e6cf-7c13-43e6-a8f6-2b46184b8ad6@gmail.com> Date: Mon, 2 Feb 2026 19:36:14 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 4/7] ACPI: CPPC: add APIs and sysfs interface for min/max_perf To: Sumit Gupta , "zhenglifeng (A)" , pierre.gondois@arm.com Cc: rafael@kernel.org, viresh.kumar@linaro.org, ionela.voinescu@arm.com, lenb@kernel.org, robert.moore@intel.com, corbet@lwn.net, rdunlap@infradead.org, ray.huang@amd.com, gautham.shenoy@amd.com, mario.limonciello@amd.com, perry.yuan@amd.com, zhanjie9@hisilicon.com, linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, acpica-devel@lists.linux.dev, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, treding@nvidia.com, jonathanh@nvidia.com, vsethi@nvidia.com, ksitaraman@nvidia.com, sanjayc@nvidia.com, nhartman@nvidia.com, bbasu@nvidia.com References: <20260129104817.3752340-1-sumitg@nvidia.com> <20260129104817.3752340-5-sumitg@nvidia.com> <4432fa04-e67c-422a-aae4-2938be431985@huawei.com> Content-Language: en-US From: Russell Haley In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/31/26 7:58 AM, Sumit Gupta wrote: > > On 31/01/26 09:36, zhenglifeng (A) wrote: >> External email: Use caution opening links or attachments >> >> >> Hi Sumit, >> >> I am thinking that maybe it is better to call these two sysfs interface >> 'min_freq' and 'max_freq' as users read and write khz instead of raw >> value. > > Thanks for the suggestion. > Kept min_perf/max_perf to match the CPPC register names > (MIN_PERF/MAX_PERF), making it clear to users familiar with > CPPC what's being controlled. > The kHz unit is documented in the ABI. > > Thank you, > Sumit Gupta On my x86 machine with kernel 6.18.5, the kernel is exposing raw values: > grep . /sys/devices/system/cpu/cpu0/acpi_cppc/* /sys/devices/system/cpu/cpu0/acpi_cppc/feedback_ctrs:ref:342904018856568 del:437439724183386 /sys/devices/system/cpu/cpu0/acpi_cppc/guaranteed_perf:63 /sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf:88 /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_freq:0 /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_nonlinear_perf:36 /sys/devices/system/cpu/cpu0/acpi_cppc/lowest_perf:1 /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_freq:3900 /sys/devices/system/cpu/cpu0/acpi_cppc/nominal_perf:62 /sys/devices/system/cpu/cpu0/acpi_cppc/reference_perf:62 /sys/devices/system/cpu/cpu0/acpi_cppc/wraparound_time:18446744073709551615 It would be surprising for a nearby sysfs interface with very similar names to use kHz instead. Thanks, Russell Haley