linux-kernel - Re: [PATCH] cpufreq: Abort cpufreq_update_current_freq() for cpufreq

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Date:	Sun, 10 Apr 2016 09:40:08 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH] cpufreq: Abort cpufreq_update_current_freq() for
 cpufreq_suspended set

On 10 April 2016 at 09:38, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Since governor operations are generally skipped if cpufreq_suspended
> is set, cpufreq_start_governor() should do nothing 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.
>
> To prevent problems from happening for this reason, make
> cpufreq_update_current_freq(), which is the only function invoked
> by cpufreq_start_governor() that doesn't check cpufreq_suspended
> already, return 0 upfront if cpufreq_suspended is set.
>
> Fixes: 3bbf8fe3ae08 (cpufreq: Always update current frequency before startig governor)
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/cpufreq/cpufreq.c |    3 +++
>  1 file changed, 3 insertions(+)
>
> Index: linux-pm/drivers/cpufreq/cpufreq.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> +++ linux-pm/drivers/cpufreq/cpufreq.c
> @@ -1565,6 +1565,9 @@ static unsigned int cpufreq_update_curre
>  {
>         unsigned int new_freq;
>
> +       if (cpufreq_suspended)
> +               return 0;
> +
>         new_freq = cpufreq_driver->get(policy->cpu);
>         if (!new_freq)
>                 return 0;

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>