linux-kernel - Re: [PATCH v3 2/3] cpufreq: Add a new function to get cpufreq policy without checking if the CPU is online

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Message-ID: <CAJZ5v0h3XKXAGHSrx50vt1Aho3uchiJ2kjQa7qCM8jCr03YKTA@mail.gmail.com>
Date: Tue, 5 Aug 2025 14:57:18 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Lifeng Zheng <zhenglifeng1@...wei.com>
Cc: catalin.marinas@....com, will@...nel.org, rafael@...nel.org, 
	viresh.kumar@...aro.org, beata.michalska@....com, sudeep.holla@....com, 
	linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linuxarm@...wei.com, 
	jonathan.cameron@...wei.com, vincent.guittot@...aro.org, 
	yangyicong@...ilicon.com, zhanjie9@...ilicon.com, lihuisong@...wei.com, 
	yubowen8@...wei.com, linhongye@...artners.com
Subject: Re: [PATCH v3 2/3] cpufreq: Add a new function to get cpufreq policy
 without checking if the CPU is online

On Tue, Aug 5, 2025 at 11:34 AM Lifeng Zheng <zhenglifeng1@...wei.com> wrote:
>
> cpufreq_cpu_get_raw() gets cpufreq policy only if the CPU is in
> policy->cpus mask, which means the CPU is already online. But in some
> cases, the policy is needed before the CPU is added to cpus mask. Add a
> function to get the policy in these cases.
>
> Signed-off-by: Lifeng Zheng <zhenglifeng1@...wei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 11 +++++++++++
>  include/linux/cpufreq.h   |  1 +
>  2 files changed, 12 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index fc7eace8b65b..2de76a072893 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -198,6 +198,17 @@ struct cpufreq_policy *cpufreq_cpu_get_raw(unsigned int cpu)
>  }
>  EXPORT_SYMBOL_GPL(cpufreq_cpu_get_raw);
>
> +struct cpufreq_policy *cpufreq_cpu_get_raw_no_check(unsigned int cpu)

This is not a particularly nice name.  Maybe call it cpufreq_cpu_policy()?

> +{
> +       struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu);
> +
> +       if (policy)
> +               return policy;
> +
> +       return NULL;

This could just be a one-liner with this statement in the function body:

  return per_cpu(cpufreq_cpu_data, cpu);

Can't it?

In which case it can be called in all places reading cpufreq_cpu_data
for a given CPU.

> +}
> +EXPORT_SYMBOL_GPL(cpufreq_cpu_get_raw_no_check);
> +
>  unsigned int cpufreq_generic_get(unsigned int cpu)
>  {
>         struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 95f3807c8c55..02ad8173dc10 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -205,6 +205,7 @@ struct cpufreq_freqs {
>
>  #ifdef CONFIG_CPU_FREQ
>  struct cpufreq_policy *cpufreq_cpu_get_raw(unsigned int cpu);
> +struct cpufreq_policy *cpufreq_cpu_get_raw_no_check(unsigned int cpu);
>  struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu);
>  void cpufreq_cpu_put(struct cpufreq_policy *policy);
>  #else
> --