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

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Date:	Sun, 10 Apr 2016 05:46:16 +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 Sun, Apr 10, 2016 at 5:16 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> 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.

That can be done too.