Re: [PATCH v2] cpufreq: cppc: Clamp default minimum limit to lowest_nonlinear_perf

[Sumit Gupta]

Hi Viresh,

Happy to help with the reviews. You can add me to the reviewers list.

Thank you,
Sumit Gupta


On 05/03/26 12:02, Viresh Kumar wrote:
> External email: Use caution opening links or attachments
>
>
> Added few more people
>
> I think we should updated MAINTAINERS with a list of reviewers or maintainers
> for the CPPC driver. Who all want to be part of the reviewers list ?
>
> On 03-03-26, 20:03, zhangpengjie (A) wrote:
> > Just a gentle ping on this patch.
> > Thanks, Pengjie
> >
> > On 2/13/2026 6:06 PM, Pengjie Zhang wrote:
> > > The ACPI spec defines 'lowest_nonlinear_perf' as the threshold for
> > > linear performance scaling. Performance levels below this threshold
> > > are typically inefficient and should not be used by default.
> > >
> > > Currently, the QoS minimum request is initialized to 0. This defaults
> > > the performance floor to the absolute "Lowest Performance" state
> > > instead of "lowest_nonlinear_perf", allowing the CPU to operate in
> > > an inefficient range unnecessarily.
> > >
> > > Signed-off-by: Pengjie Zhang <zhangpengjie2@xxxxxxxxxx>
> > > ---
> > > Changes in v2:
> > >     - Renamed the patch subject to better reflect the logic change.
> > >     - Updated the commit log to clarify ACPI spec details.
> > > Link to v1:https://lore.kernel.org/all/20260116094555.2978887-1-zhangpengjie2@xxxxxxxxxx/
> > > ---
> > >    drivers/cpufreq/cppc_cpufreq.c | 18 ++++++++++++++++--
> > >    1 file changed, 16 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> > > index 7e8042efedd1..4a3031d9fcf4 100644
> > > --- a/drivers/cpufreq/cppc_cpufreq.c
> > > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > > @@ -333,9 +333,23 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
> > >      return target_freq;
> > >    }
> > > -static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> > > +static int cppc_verify_policy(struct cpufreq_policy_data *policy_data)
> > >    {
> > > -   cpufreq_verify_within_cpu_limits(policy);
> > > +   if (policy_data->min == FREQ_QOS_MIN_DEFAULT_VALUE) {
> > > +           struct cpufreq_policy *policy __free(put_cpufreq_policy) =
> > > +                                         cpufreq_cpu_get(policy_data->cpu);
> > > +           struct cppc_cpudata *cpu_data;
> > > +
> > > +           if (!policy)
> > > +                   return -EINVAL;
> > > +
> > > +           cpu_data = policy->driver_data;
> > > +           policy_data->min = cppc_perf_to_khz(&cpu_data->perf_caps,
> > > +                   cpu_data->perf_caps.lowest_nonlinear_perf);
> > > +   }
> > > +
> > > +   cpufreq_verify_within_cpu_limits(policy_data);
> > > +
> > >      return 0;
> > >    }
> --
> viresh