linux-kernel - Re: [PATCH v3 6/8] cpufreq: CPPC: Add sysfs for min/max_perf and perf

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ee56e056-3c7e-4df7-9186-fc458d4379eb@nvidia.com>
Date: Fri, 24 Oct 2025 19:02:07 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: Ionela Voinescu <ionela.voinescu@....com>
Cc: rafael@...nel.org, viresh.kumar@...aro.org, lenb@...nel.org,
 robert.moore@...el.com, corbet@....net, pierre.gondois@....com,
 zhenglifeng1@...wei.com, rdunlap@...radead.org, 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, 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 v3 6/8] cpufreq: CPPC: Add sysfs for min/max_perf and
 perf_limited


On 22/10/25 17:32, Ionela Voinescu wrote:
> External email: Use caution opening links or attachments
>
>
> Hi,
>
> On Wednesday 01 Oct 2025 at 20:31:02 (+0530), Sumit Gupta wrote:
>> Add sysfs interfaces for Minimum Performance, Maximum Performance
>> and Performance Limited Register in the cppc_cpufreq driver.
>>
>> Reviewed-by: Randy Dunlap <rdunlap@...radead.org>
>> 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..82141b45d58c 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:                September 2025
>> +Contact:     linux-pm@...r.kernel.org
>> +Description: Minimum Performance
>> +
>> +             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.
> In the ACPI specification I don't see a clear dependency between the
> minimum and maximum performance registers and autonomous selection.
> There's nothing to say that min and max do not have meaning with
> autonomous selection is disabled.
>
> Thanks,
> Ionela. 

Yes, will remove the text about dependency on autonomous selection in v4.

Thank you,
Sumit Gupta


>> +
>> +             This file is only present if the cppc-cpufreq driver is in use.
>> +
>> +What:                /sys/devices/system/cpu/cpuX/cpufreq/max_perf
>> +Date:                September 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:                September 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
>> --
>> 2.34.1
>>
>>