linux-kernel - Re: [PATCH] cpufreq: Skip all governor-related actions for cpufreq

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Date:	Sun, 10 Apr 2016 08:46:46 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] cpufreq: Skip all governor-related actions for
 cpufreq_suspended set

On 08-04-16, 23:54, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: [PATCH] cpufreq: Skip all governor-related actions for cpufreq_suspended set
> 
> Since governor operations are generally skipped if cpufreq_suspended
> is set, do nothing at all in cpufreq_start_governor() in that case.
> 
> That function is called in the cpufreq_online() path, and may also
> be called from cpufreq_offline() in some cases, which are invoked
> by the nonboot CPUs disabing/enabling code during system suspend
> to RAM and resume.  That happens when all devices have been
> suspended, so if the cpufreq driver relies on things like I2C to
> get the current frequency, it may not be ready to do that then.
> 
> The change here prevents problems from happening for this reason.
> 
> Fixes: 3bbf8fe3ae08 (cpufreq: Always update current frequency before startig governor)
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> Index: linux-pm/drivers/cpufreq/cpufreq.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> +++ linux-pm/drivers/cpufreq/cpufreq.c
> @@ -2053,6 +2053,9 @@ static int cpufreq_start_governor(struct
>  {
>  	int ret;
>  
> +	if (cpufreq_suspended)
> +		return 0;
> +
>  	if (cpufreq_driver->get && !cpufreq_driver->setpolicy)
>  		cpufreq_update_current_freq(policy);

Since we no longer have the same check in cpufreq_exit_governor(),
what about moving it to cpufreq_update_current_freq() instead? That's
all we are trying to protect here anyway, as cpufreq_governor() is
already protected.

-- 
viresh