linux-kernel - Re: [RFC][PATCH 1/2] cpufreq: Add special-purpose fast-switching callback for drivers

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Date:   Mon, 7 Dec 2020 14:40:52 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Doug Smythies <dsmythies@...us.net>,
        Giovanni Gherdovich <ggherdovich@...e.com>
Subject: Re: [RFC][PATCH 1/2] cpufreq: Add special-purpose fast-switching
 callback for drivers

On Mon, Dec 7, 2020 at 8:47 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 30-11-20, 19:37, Rafael J. Wysocki wrote:
> > Index: linux-pm/include/linux/cpufreq.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/cpufreq.h
> > +++ linux-pm/include/linux/cpufreq.h
> > @@ -320,6 +320,15 @@ struct cpufreq_driver {
> >                                       unsigned int index);
> >       unsigned int    (*fast_switch)(struct cpufreq_policy *policy,
> >                                      unsigned int target_freq);
> > +     /*
> > +      * ->fast_switch() replacement for drivers that use an internal
> > +      * representation of performance levels and can pass hints other than
> > +      * the target performance level to the hardware.
> > +      */
> > +     void            (*adjust_perf)(unsigned int cpu, bool busy,
>
> Maybe this should still take policy as an argument (like other calls)
> instead of CPU, even if it is going to be used for single-cpu per
> policy case for now.

That can be changed in the future if need be.

Otherwise this path doesn't need to look at the policy object at all
and I'd rather keep it this way.

>
> > +                                    unsigned long min_perf,
> > +                                    unsigned long target_perf,
> > +                                    unsigned long capacity);
>
> --