linux-kernel - Re: [PATCH v7 4/7] ACPI: CPPC: add APIs and sysfs interface for min/max

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Message-ID: <944fc140-e5c5-425f-a6ad-883e87eed8a3@nvidia.com>
Date: Tue, 3 Feb 2026 15:11:20 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: Russell Haley <yumpusamongus@...il.com>,
 "zhenglifeng (A)" <zhenglifeng1@...wei.com>, pierre.gondois@....com,
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: rafael@...nel.org, viresh.kumar@...aro.org, ionela.voinescu@....com,
 lenb@...nel.org, robert.moore@...el.com, corbet@....net,
 rdunlap@...radead.org, ray.huang@....com, gautham.shenoy@....com,
 mario.limonciello@....com, perry.yuan@....com, zhanjie9@...ilicon.com,
 linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-doc@...r.kernel.org, acpica-devel@...ts.linux.dev,
 linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
 treding@...dia.com, jonathanh@...dia.com, vsethi@...dia.com,
 ksitaraman@...dia.com, sanjayc@...dia.com, nhartman@...dia.com,
 bbasu@...dia.com, sumitg@...dia.com
Subject: Re: [PATCH v7 4/7] ACPI: CPPC: add APIs and sysfs interface for
 min/max_perf

>>> 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

I can rename to either of the below:
- min/max_freq: might be confused with scaling_min/max_freq.
- min/max_perf_freq: keeps the CPPC register association clear.

Rafael, Any preferences here?

Thank you,
Sumit Gupta