Re: [PATCH v5 10/11] cpufreq: CPPC: make scaling_min/max_freq read-only when auto_sel enabled

[Sumit Gupta]

On 26/12/25 08:56, zhenglifeng (A) wrote:
> External email: Use caution opening links or attachments
>
>
> On 2025/12/23 20:13, Sumit Gupta wrote:
> > When autonomous selection (auto_sel) is enabled, the hardware controls
> > performance within min_perf/max_perf register bounds making the
> > scaling_min/max_freq effectively read-only.
> >
> > Enforce this by setting policy limits to min/max_perf bounds in
> > cppc_verify_policy(). Users must use min_perf/max_perf sysfs interfaces
> > to change performance limits in autonomous mode.
> >
> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   drivers/cpufreq/cppc_cpufreq.c | 32 +++++++++++++++++++++++++++++++-
> >   1 file changed, 31 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> > index b1f570d6de34..b3da263c18b0 100644
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > @@ -305,7 +305,37 @@ static unsigned int cppc_cpufreq_fast_switch(struct cpufreq_policy *policy,
> >
> >   static int cppc_verify_policy(struct cpufreq_policy_data *policy)
> >   {
> > -     cpufreq_verify_within_cpu_limits(policy);
> > +     unsigned int min_freq = policy->cpuinfo.min_freq;
> > +     unsigned int max_freq = policy->cpuinfo.max_freq;
> > +     struct cpufreq_policy *cpu_policy;
> > +     struct cppc_cpudata *cpu_data;
> > +     struct cppc_perf_caps *caps;
> > +
> > +     cpu_policy = cpufreq_cpu_get(policy->cpu);
> Better to use:
>
>          struct cpufreq_policy *cpu_policy __free(put_cpufreq_policy) = cpufreq_cpu_get(policy->cpu);

Will use this in v6.


> > +     if (!cpu_policy)
> > +             return -ENODEV;
> > +
> > +     cpu_data = cpu_policy->driver_data;
> > +     caps = &cpu_data->perf_caps;
> cpu_policy, cpu_data and cpas are only used in the if branch. Just put them
> in it.

Can move caps inside the if branch.
cpu_policy and cpu_data can't be moved inside because we need
perf_ctrls.auto_sel to evaluate the condition itself.

> > +
> > +     if (cpu_data->perf_ctrls.auto_sel) {
> > +             u32 min_perf, max_perf;
> > +
> > +             /*
> > +              * Set policy limits to HW min/max_perf bounds. In autonomous
> > +              * mode, scaling_min/max_freq is effectively read-only.
> > +              */
> > +             min_perf = cpu_data->perf_ctrls.min_perf ?:
> > +                        caps->lowest_nonlinear_perf;
> > +             max_perf = cpu_data->perf_ctrls.max_perf ?: caps->nominal_perf;
> > +
> > +             policy->min = cppc_perf_to_khz(caps, min_perf);
> > +             policy->max = cppc_perf_to_khz(caps, max_perf);
> > +     } else {
> > +             cpufreq_verify_within_limits(policy, min_freq, max_freq);
> Why not still using cpufreq_verify_within_cpu_limits()?

Will change to use it in v6.

Thank you,
Sumit Gupta

> > +     }
> > +
> > +     cpufreq_cpu_put(cpu_policy);
> >        return 0;
> >   }