linux-kernel - Re: [PATCH 5/8] cpufreq: report whether cpufreq supports Frequency Invariance (FI)

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Message-ID: <20200701104620.lxhxty7gymjlagp6@vireshk-i7>
Date:   Wed, 1 Jul 2020 16:16:20 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     rjw@...ysocki.net, catalin.marinas@....com, sudeep.holla@....com,
        will@...nel.org, linux@...linux.org.uk, valentin.schneider@....com,
        mingo@...hat.com, peterz@...radead.org, dietmar.eggemann@....com,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/8] cpufreq: report whether cpufreq supports Frequency
 Invariance (FI)

On 01-07-20, 10:07, Ionela Voinescu wrote:
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 83b58483a39b..60b5272c5d80 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -59,6 +59,9 @@ static struct cpufreq_driver *cpufreq_driver;
>  static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
>  static DEFINE_RWLOCK(cpufreq_driver_lock);
>  
> +/* Mark support for the scheduler's frequency invariance engine */
> +static DEFINE_STATIC_KEY_FALSE(cpufreq_set_freq_scale);
> +
>  /* Flag to suspend/resume CPUFreq governors */
>  static bool cpufreq_suspended;
>  
> @@ -67,6 +70,26 @@ static inline bool has_target(void)
>  	return cpufreq_driver->target_index || cpufreq_driver->target;
>  }
>  
> +static inline
> +void enable_cpufreq_freq_invariance(struct cpufreq_driver *driver)
> +{
> +	if ((driver->flags & CPUFREQ_CUSTOM_SET_FREQ_SCALE) ||
> +	    ((driver->target_index || driver->fast_switch)
> +	     && !(driver->target || driver->setpolicy))) {

This will get simplified with the way I suggested it I believe.

> +
> +		static_branch_enable_cpuslocked(&cpufreq_set_freq_scale);
> +		pr_debug("%s: Driver %s can provide frequency invariance.",
> +			 __func__, driver->name);
> +	} else
> +		pr_err("%s: Driver %s cannot provide frequency invariance.",
> +		__func__, driver->name);
> +}
> +
> +bool cpufreq_sets_freq_scale(void)
> +{
> +	return static_branch_likely(&cpufreq_set_freq_scale);
> +}
> +
>  /* internal prototypes */
>  static unsigned int __cpufreq_get(struct cpufreq_policy *policy);
>  static int cpufreq_init_governor(struct cpufreq_policy *policy);
> @@ -2713,6 +2736,8 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
>  	cpufreq_driver = driver_data;
>  	write_unlock_irqrestore(&cpufreq_driver_lock, flags);
>  
> +	enable_cpufreq_freq_invariance(cpufreq_driver);
> +
>  	if (driver_data->setpolicy)
>  		driver_data->flags |= CPUFREQ_CONST_LOOPS;
>  
> @@ -2782,6 +2807,7 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
>  	cpus_read_lock();
>  	subsys_interface_unregister(&cpufreq_interface);
>  	remove_boost_sysfs_file();
> +	static_branch_disable_cpuslocked(&cpufreq_set_freq_scale);
>  	cpuhp_remove_state_nocalls_cpuslocked(hp_online);
>  
>  	write_lock_irqsave(&cpufreq_driver_lock, flags);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 42668588f9f8..8b6369d657bd 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -217,6 +217,7 @@ void refresh_frequency_limits(struct cpufreq_policy *policy);
>  void cpufreq_update_policy(unsigned int cpu);
>  void cpufreq_update_limits(unsigned int cpu);
>  bool have_governor_per_policy(void);
> +bool cpufreq_sets_freq_scale(void);
>  struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
>  void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
>  void cpufreq_disable_fast_switch(struct cpufreq_policy *policy);
> @@ -237,6 +238,10 @@ static inline unsigned int cpufreq_get_hw_max_freq(unsigned int cpu)
>  {
>  	return 0;
>  }
> +static inline bool cpufreq_sets_freq_scale(void)
> +{
> +	return false;
> +}
>  static inline void disable_cpufreq(void) { }
>  #endif
>  
> -- 
> 2.17.1

-- 
viresh