linux-kernel - Re: [PATCH v3 2/6] cpufreq: use the fixed and coherent frequency for scaling capacity

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Date:   Wed, 18 Oct 2023 19:23:13 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, sudeep.holla@....com,
        gregkh@...uxfoundation.org, rafael@...nel.org, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        viresh.kumar@...aro.org, lenb@...nel.org, robert.moore@...el.com,
        lukasz.luba@....com, ionela.voinescu@....com,
        pierre.gondois@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
        acpica-devel@...ts.linuxfoundation.org, conor.dooley@...rochip.com,
        suagrfillet@...il.com, ajones@...tanamicro.com, lftan@...nel.org
Subject: Re: [PATCH v3 2/6] cpufreq: use the fixed and coherent frequency for
 scaling capacity

On Wed, Oct 18, 2023 at 6:25 PM Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>
> cpuinfo.max_freq can change at runtime because of boost as an example. This
> implies that the value could be different from the frequency that has been
> used to compute the capacity of a CPU.
>
> The new arch_scale_freq_ref() returns a fixed and coherent frequency
> that can be used to compute the capacity for a given frequency.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> Reviewed-by: Lukasz Luba <lukasz.luba@....com>
> Tested-by: Lukasz Luba <lukasz.luba@....com>

Acked-by: Rafael J. Wysocki <rafael@...nel.org>

> ---
>  drivers/cpufreq/cpufreq.c | 4 ++--
>  include/linux/cpufreq.h   | 9 +++++++++
>  2 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 60ed89000e82..8c4f9c2f9c44 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -454,7 +454,7 @@ void cpufreq_freq_transition_end(struct cpufreq_policy *policy,
>
>         arch_set_freq_scale(policy->related_cpus,
>                             policy->cur,
> -                           policy->cpuinfo.max_freq);
> +                           arch_scale_freq_ref(policy->cpu));
>
>         spin_lock(&policy->transition_lock);
>         policy->transition_ongoing = false;
> @@ -2174,7 +2174,7 @@ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
>
>         policy->cur = freq;
>         arch_set_freq_scale(policy->related_cpus, freq,
> -                           policy->cpuinfo.max_freq);
> +                           arch_scale_freq_ref(policy->cpu));
>         cpufreq_stats_record_transition(policy, freq);
>
>         if (trace_cpu_frequency_enabled()) {
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 71d186d6933a..bbc483b4b6e5 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -1211,6 +1211,15 @@ void arch_set_freq_scale(const struct cpumask *cpus,
>  {
>  }
>  #endif
> +
> +#ifndef arch_scale_freq_ref
> +static __always_inline
> +unsigned int arch_scale_freq_ref(int cpu)
> +{
> +       return 0;
> +}
> +#endif
> +
>  /* the following are really really optional */
>  extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;
>  extern struct freq_attr cpufreq_freq_attr_scaling_boost_freqs;
> --
> 2.34.1
>