linux-kernel - Re: [PATCH v2 2/2] cpufreq: Wire-up arch-flavored freq info into cpufreq_verify_current

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Message-ID: <CAJZ5v0jh3mG3hyFS6war=0bk3PvsVtTwZ1_YwwWov36Bmz7q0w@mail.gmail.com>
Date:   Wed, 6 Dec 2023 21:41:05 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Beata Michalska <beata.michalska@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, sumitg@...dia.com, sudeep.holla@....covm,
        will@...nel.org, catalin.marinas@....com, viresh.kumar@...aro.org,
        rafael@...nel.org, ionela.voinescu@....com,
        yang@...amperecomputing.com, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v2 2/2] cpufreq: Wire-up arch-flavored freq info into cpufreq_verify_current_freq

On Mon, Nov 27, 2023 at 5:09 PM Beata Michalska <beata.michalska@....com> wrote:
>
> From: Sumit Gupta <sumitg@...dia.com>
>
> When available, use arch_freq_get_on_cpu to obtain current frequency
> (usually an average reported over given period of time)
> to better align the cpufreq's view on the current state of affairs.

And why is this a good idea?

Any problem statement?

> This also automatically pulls in the update for cpuinfo_cur_freq sysfs
> attribute, aligning it with the scaling_cur_freq one, and thus providing
> consistent view on relevant platforms.

I have no idea what the above is supposed to mean, sorry.

> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> [BM: Subject & commit msg]
> Signed-off-by: Beata Michalska <beata.michalska@....com>
> ---
>  drivers/cpufreq/cpufreq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 8c4f9c2f9c44..109559438f45 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1756,7 +1756,8 @@ static unsigned int cpufreq_verify_current_freq(struct cpufreq_policy *policy, b
>  {
>         unsigned int new_freq;
>
> -       new_freq = cpufreq_driver->get(policy->cpu);
> +       new_freq = arch_freq_get_on_cpu(policy->cpu);
> +       new_freq = new_freq ?: cpufreq_driver->get(policy->cpu);

Please don't use ?: in general and it is not even useful here AFAICS.

What would be wrong with

new_freq = arch_freq_get_on_cpu(policy->cpu);
if (!new_freq)
        new_freq = cpufreq_driver->get(policy->cpu);

?

>         if (!new_freq)
>                 return 0;
>
> --