Re: [PATCH v2] cpufreq: intel_pstate: set stale CPU frequency to minimum

[Keyon Jie]

On 8/22/23 04:46, Rafael J. Wysocki wrote:
> On Sun, Aug 20, 2023 at 10:46 PM Doug Smythies <dsmythies@xxxxxxxxx> wrote:
> > The intel_pstate CPU frequency scaling driver does not
> > use policy->cur and it is 0.
> > When the CPU frequency is outdated arch_freq_get_on_cpu()
> > will default to the nominal clock frequency when its call to
> > cpufreq_quick_getpolicy_cur returns the never updated 0.
> > Thus, the listed frequency might be outside of currently
> > set limits. Some users are complaining about the high
> > reported frequency, albeit stale, when their system is
> > idle and/or it is above the reduced maximum they have set.
> >
> > This patch will maintain policy_cur for the intel_pstate
> > driver at the current minimum CPU frequency.
> >
> > Reported-by: Yang Jie <yang.jie@xxxxxxxxxxxxxxx>
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217597
> > Signed-off-by: Doug Smythies <dsmythies@xxxxxxxxx>
> > ---
> >
> > v1 -> v2:
> >     * v1 was a completely different approach, programming around
> >       the issue rather than fixing it at the source.
> >       reference:
> >       https://patchwork.kernel.org/project/linux-pm/patch/006901d9be8c$f4439930$dccacb90$@telus.net/
> >     * v2 does not fix an issue with the intel_cpufreq CPU scaling
> >       driver (A.K.A. the intel_pstate driver in passive mode) and
> >       the schedutil CPU frequency scaling governor when HWP is enabled
> >       where limit changes are not reflected in the stale listed frequencies.
> >       A fix for that will be some future patch.
> >
> > ---
> >   drivers/cpufreq/intel_pstate.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> > index 8ca2bce4341a..08284dee583a 100644
> > --- a/drivers/cpufreq/intel_pstate.c
> > +++ b/drivers/cpufreq/intel_pstate.c
> > @@ -2609,6 +2609,11 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
> >                          intel_pstate_clear_update_util_hook(policy->cpu);
> >                  intel_pstate_hwp_set(policy->cpu);
> >          }
> > +       /* policy current is never updated with the intel_pstate driver
> > +        * but it is used as a stale frequency value. So, keep it within
> > +        * limits.
> > +        */
> > +       policy->cur = policy->min;
> >
> >          mutex_unlock(&intel_pstate_limits_lock);
> >
> > --
>
> Applied as 6.6 material, with some mailer-induced white space damage
> fixed and the new comment adjusted to the kernel coding style.
>
> Thanks!

Hi Doug and Rafael,

Thank you for making the fix happen.

Hi Greg,

Will this be picked to the stable linux-6.1.y and linux-6.4.y kernel, it 
could benefit to users there.

Thanks,
~Keyon