linux-kernel - Re: [PATCH v3 2/4] cpufreq: introduce cpufreq_driver_might

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Date:	Fri, 26 Jun 2015 19:48:31 -0500
From:	Felipe Balbi <balbi@...com>
To:	Michael Turquette <mturquette@...libre.com>
CC:	<peterz@...radead.org>, <mingo@...nel.org>,
	<linux-kernel@...r.kernel.org>, <preeti@...ux.vnet.ibm.com>,
	<Morten.Rasmussen@....com>, <riel@...hat.com>, <efault@....de>,
	<nicolas.pitre@...aro.org>, <daniel.lezcano@...aro.org>,
	<dietmar.eggemann@....com>, <vincent.guittot@...aro.org>,
	<amit.kucheria@...aro.org>, <juri.lelli@....com>,
	<rjw@...ysocki.net>, <viresh.kumar@...aro.org>,
	<ashwin.chaugule@...aro.org>, <alex.shi@...aro.org>,
	<linux-pm@...r.kernel.org>, <abelvesa@...il.com>,
	<pebolle@...cali.nl>, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v3 2/4] cpufreq: introduce cpufreq_driver_might_sleep

Hi,

On Fri, Jun 26, 2015 at 04:53:42PM -0700, Michael Turquette wrote:
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 28e59a4..e5296c0 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -112,6 +112,12 @@ bool have_governor_per_policy(void)
>  }
>  EXPORT_SYMBOL_GPL(have_governor_per_policy);
>  
> +bool cpufreq_driver_might_sleep(void)
> +{
> +	return !(cpufreq_driver->flags & CPUFREQ_DRIVER_WILL_NOT_SLEEP);
> +}
> +EXPORT_SYMBOL_GPL(cpufreq_driver_might_sleep);
> +
>  struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy)
>  {
>  	if (have_governor_per_policy())
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 2ee4888..1f2c9a1 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -157,6 +157,7 @@ u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy);
>  int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu);
>  int cpufreq_update_policy(unsigned int cpu);
>  bool have_governor_per_policy(void);
> +bool cpufreq_driver_might_sleep(void);
>  struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
>  #else
>  static inline unsigned int cpufreq_get(unsigned int cpu)
> @@ -314,6 +315,14 @@ struct cpufreq_driver {
>   */
>  #define CPUFREQ_NEED_INITIAL_FREQ_CHECK	(1 << 5)
>  
> +/*
> + * Set by drivers that will never block or sleep during their frequency
> + * transition. Used to indicate when it is safe to call cpufreq_driver_target
> + * from non-interruptable context. Drivers must opt-in to this flag, as the
> + * safe default is that they might sleep.
> + */
> +#define CPUFREQ_DRIVER_WILL_NOT_SLEEP	(1 << 6)

don't you need to update current drivers and pass this flag where
necessary ?

-- 
balbi

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