Re: [PATCH v3 6/8] cpufreq: CPPC: Add sysfs for min/max_perf and perf_limited

[Sumit Gupta]

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@xxxxxxxxxxxxx>
> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   .../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@xxxxxxxxxxxxxxx
> > +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@xxxxxxxxxxxxxxx
> > +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@xxxxxxxxxxxxxxx
> > +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