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

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Date:	Thu, 7 Apr 2016 13:22:39 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	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 Thu, Apr 7, 2016 at 6:28 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 07-04-16, 03:29, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> Since governor operations are generally skipped if cpufreq_suspended
>> is set, do nothing at all in cpufreq_start_governor() and
>> cpufreq_exit_governor() in that case.
>>
>> In particular, this prevents fast frequency switching from being
>> disabled after a suspend-to-RAM cycle on all CPUs except for the
>> boot one.
>
> static int cpufreq_governor(struct cpufreq_policy *policy, unsigned int event)
> {
>         int ret;
>
>         /* Don't start any governor operations if we are entering suspend */
>         if (cpufreq_suspended)
>                 return 0;
>
>         ...
>
> }
>
> Above already guarantees that we would start/stop governors. Why do we
> need this change then ?

Because we do extra stuff in cpufreq_start_governor() and
cpufreq_exit_governor() that *also* shouldn't be done if
cpufreq_suspended is set.