linux-kernel - Re: [PATCH v4 03/18] PM: EM: Find first CPU online while updating OPP efficiency

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Message-ID: <CAJZ5v0h6AsQCrtJ1b5VoWD_=yTKC=Y0e5KqSHy5GsFt-H7NFXA@mail.gmail.com>
Date:   Tue, 26 Sep 2023 20:32:33 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rafael@...nel.org, dietmar.eggemann@....com, rui.zhang@...el.com,
        amit.kucheria@...durent.com, amit.kachhap@...il.com,
        daniel.lezcano@...aro.org, viresh.kumar@...aro.org,
        len.brown@...el.com, pavel@....cz, mhiramat@...nel.org,
        qyousef@...alina.io, wvw@...gle.com
Subject: Re: [PATCH v4 03/18] PM: EM: Find first CPU online while updating OPP efficiency

On Mon, Sep 25, 2023 at 10:11 AM Lukasz Luba <lukasz.luba@....com> wrote:
>
> The Energy Model might be updated at runtime and the energy efficiency
> for each OPP may change. Thus, there is a need to update also the
> cpufreq framework and make it aligned to the new values. In order to
> do that, use a first online CPU from the Performance Domain.
>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  kernel/power/energy_model.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
> index 42486674b834..3dafdd7731c4 100644
> --- a/kernel/power/energy_model.c
> +++ b/kernel/power/energy_model.c
> @@ -243,12 +243,19 @@ em_cpufreq_update_efficiencies(struct device *dev, struct em_perf_state *table)
>         struct em_perf_domain *pd = dev->em_pd;
>         struct cpufreq_policy *policy;
>         int found = 0;
> -       int i;
> +       int i, cpu;
>
>         if (!_is_cpu_device(dev) || !pd)
>                 return;
>
> -       policy = cpufreq_cpu_get(cpumask_first(em_span_cpus(pd)));
> +       /* Try to get a CPU which is online and in this PD */
> +       cpu = cpumask_first_and(em_span_cpus(pd), cpu_active_mask);

The comment talks about "online" and cpu_active_mask is used.  Isn't
it a bit inconsistent?

> +       if (cpu >= nr_cpu_ids) {
> +               dev_warn(dev, "EM: No online CPU for CPUFreq policy\n");
> +               return;
> +       }
> +
> +       policy = cpufreq_cpu_get(cpu);
>         if (!policy) {
>                 dev_warn(dev, "EM: Access to CPUFreq policy failed\n");
>                 return;
> --
> 2.25.1
>