linux-kernel - Re: [PATCH V2 1/9] cpufreq: Auto-register with energy model if asked

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Message-ID: <YRPKgdVxM7Mytf75@google.com>
Date:   Wed, 11 Aug 2021 14:02:57 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/9] cpufreq: Auto-register with energy model if asked

On Wednesday 11 Aug 2021 at 17:28:39 (+0530), Viresh Kumar wrote:
> Many cpufreq drivers register with the energy model for each policy and
> do exactly the same thing. Follow the footsteps of thermal-cooling, to
> get it done from the cpufreq core itself.
> 
> Provide a new callback, which will be called, if present, by the cpufreq
> core at the right moment (more on that in the code's comment). Also
> provide a generic implementation that uses dev_pm_opp_of_register_em().
> 
> This also allows us to register with the EM at a later point of time,
> compared to ->init(), from where the EM core can access cpufreq policy
> directly using cpufreq_cpu_get() type of helpers and perform other work,
> like marking few frequencies inefficient, this will be done separately.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 12 ++++++++++++
>  include/linux/cpufreq.h   | 14 ++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 06c526d66dd3..75974e7d6cc5 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1493,6 +1493,18 @@ static int cpufreq_online(unsigned int cpu)
>  		write_unlock_irqrestore(&cpufreq_driver_lock, flags);
>  	}
>  
> +	/*
> +	 * Register with the energy model before sched_cpufreq_governor_change()
> +	 * is called, which will result in rebuilding of the sched domains,
> +	 * which should only be done once the energy model is properly
> +	 * initialized for the policy first.
> +	 *
> +	 * Also, this should be called before the policy is registered with
> +	 * cooling framework.
> +	 */
> +	if (cpufreq_driver->register_em)
> +		cpufreq_driver->register_em(policy);

Maybe move that to the 'if (new_policy)' block above? There is currently
no need to re-register the EM on CPU hotplug.

>  	ret = cpufreq_init_policy(policy);
>  	if (ret) {
>  		pr_err("%s: Failed to initialize policy for cpu: %d (%d)\n",
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 9fd719475fcd..1295621f6c28 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -9,10 +9,12 @@
>  #define _LINUX_CPUFREQ_H
>  
>  #include <linux/clk.h>
> +#include <linux/cpu.h>
>  #include <linux/cpumask.h>
>  #include <linux/completion.h>
>  #include <linux/kobject.h>
>  #include <linux/notifier.h>
> +#include <linux/pm_opp.h>
>  #include <linux/pm_qos.h>
>  #include <linux/spinlock.h>
>  #include <linux/sysfs.h>
> @@ -373,6 +375,12 @@ struct cpufreq_driver {
>  	/* platform specific boost support code */
>  	bool		boost_enabled;
>  	int		(*set_boost)(struct cpufreq_policy *policy, int state);
> +
> +	/*
> +	 * Set by drivers that want the core to automatically register the
> +	 * policy's devices with Energy Model.
> +	 */
> +	void		(*register_em)(struct cpufreq_policy *policy);
>  };
>  
>  /* flags */
> @@ -1046,4 +1054,10 @@ unsigned int cpufreq_generic_get(unsigned int cpu);
>  void cpufreq_generic_init(struct cpufreq_policy *policy,
>  		struct cpufreq_frequency_table *table,
>  		unsigned int transition_latency);
> +
> +static inline void cpufreq_register_em_with_opp(struct cpufreq_policy *policy)
> +{
> +	dev_pm_opp_of_register_em(get_cpu_device(policy->cpu),
> +				  policy->related_cpus);
> +}

I was thinking this could go in pm_opp.h instead, but it doesn't really
matter.

So, with the first comment above fixed:

Reviewed-by: Quentin Perret <qperret@...gle.com>

Thanks,
Quentin