linux-kernel - Re: [PATCH v2 6/7] cpufreq: CPPC: Add sysfs for min/max_perf and perf

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Message-ID: <c40e11b1-afa3-437e-a308-4648f19627a8@nvidia.com>
Date: Mon, 1 Sep 2025 18:42:09 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: Randy Dunlap <rdunlap@...radead.org>, rafael@...nel.org,
 viresh.kumar@...aro.org, lenb@...nel.org, robert.moore@...el.com,
 corbet@....net, pierre.gondois@....com, zhenglifeng1@...wei.com,
 ray.huang@....com, gautham.shenoy@....com, mario.limonciello@....com,
 perry.yuan@....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
Cc: linux-tegra@...r.kernel.org, treding@...dia.com, jonathanh@...dia.com,
 vsethi@...dia.com, ksitaraman@...dia.com, sanjayc@...dia.com,
 bbasu@...dia.com, sumitg@...dia.com
Subject: Re: [PATCH v2 6/7] cpufreq: CPPC: Add sysfs for min/max_perf and
 perf_limited


On 24/08/25 05:38, Randy Dunlap wrote:
>
> On 8/23/25 1:01 PM, Sumit Gupta wrote:
>> Add sysfs interfaces for Minimum Performance, Maximum Performance
>> and Performance Limited Register in the cppc_cpufreq driver.
>>
>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
>> ---
>>   .../ABI/testing/sysfs-devices-system-cpu      | 43 +++++++++++++++++++
>>   1 file changed, 43 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
>> index ab8cd337f43a..4bce0dbc48c9 100644
>> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
>> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
>> @@ -327,6 +327,49 @@ Description:	Energy performance preference
>>   
>>   		This file is only present if the cppc-cpufreq driver is in use.
>>   
>> +What:           /sys/devices/system/cpu/cpuX/cpufreq/min_perf
>> +Date:           Aug 2025
>> +Contact:        linux-pm@...r.kernel.org
>> +Description:    Minimum Performance
> Preferably these 4 lines above use tab(s) after the ':' for indentation
> instead of spaces. (in 3 places, i.e., each sysfs file entry).

Sorry for replying late as I was on vacation.

Sure, will replace spaces with tabs in v3 and add your 'Reviewed-by'.


Thank you,

Sumit Gupta


>> +
>> +		Read/write a 32 bits value from/to this file. This file
>> +		conveys the minimum performance level at which the platform
>> +		may run. Minimum performance may be set to any performance
>> +		value in the range [Lowest Performance, Highest Performance],
>> +		inclusive but must be set to a value that is less than or
>> +		equal to that specified by the Maximum Performance Register.
>> +
>> +		Writing to this file only has meaning when Autonomous Selection
>> +		is enabled.
>> +
>> +		This file is only present if the cppc-cpufreq driver is in use.
>> +
>> +What:           /sys/devices/system/cpu/cpuX/cpufreq/max_perf
>> +Date:           Aug 2025
>> +Contact:        linux-pm@...r.kernel.org
>> +Description:    Minimum Performance
>> +
>> +		Read/write a 32 bits value from/to this file. This file conveys
>> +		the maximum performance level at which the platform may run.
>> +		Maximum performance may be set to any performance value in the
>> +		range [Lowest Performance, Highest Performance], inclusive.
>> +
>> +		Writing to this file only has meaning when Autonomous Selection is
>> +		enabled.
>> +
>> +		This file is only present if the cppc-cpufreq driver is in use.
>> +
>> +What:           /sys/devices/system/cpu/cpuX/cpufreq/perf_limited
>> +Date:           Aug 2025
>> +Contact:        linux-pm@...r.kernel.org
>> +Description:    Minimum Performance
>> +
>> +		Read/write a 32 bits value from/to this file. This file indicates
>> +		to OSPM that an unpredictable event has limited processor
>> +		performance, and the delivered performance may be less than
>> +		desired/minimum performance.
>> +
>> +		This file is only present if the cppc-cpufreq driver is in use.
>>   
>>   What:		/sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
>>   Date:		August 2008
> Reviewed-by: Randy Dunlap <rdunlap@...radead.org>
>
> Thanks.
>