Re: [PATCH] cpufreq: skip cpufreq resume if it's not suspended

[Saravana Kannan]

On 02/02/2018 03:54 AM, Rafael J. Wysocki wrote:
> On Wednesday, January 24, 2018 9:53:14 PM CET Bo Yan wrote:
> > On 01/23/2018 06:02 PM, Rafael J. Wysocki wrote:
> > > On Tuesday, January 23, 2018 10:57:55 PM CET Bo Yan wrote:
> > > >    drivers/cpufreq/cpufreq.c | 4 ++++
> > > >    1 file changed, 4 insertions(+)
> > > >
> > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > > > index 41d148af7748..95b1c4afe14e 100644
> > > > --- a/drivers/cpufreq/cpufreq.c
> > > > +++ b/drivers/cpufreq/cpufreq.c
> > > > @@ -1680,6 +1680,10 @@ void cpufreq_resume(void)
> > > >    	if (!cpufreq_driver)
> > > >    		return;
> > > >
> > > > +	if (unlikely(!cpufreq_suspended)) {
> > > > +		pr_warn("%s: resume after failing suspend\n", __func__);
> > > > +		return;
> > > > +	}
> > > >    	cpufreq_suspended = false;
> > > >
> > > >    	if (!has_target() && !cpufreq_driver->resume)
> > > Good catch, but rather than doing this it would be better to avoid
> > > calling cpufreq_resume() at all if cpufreq_suspend() has not been called.
> > Yes, I thought about that, but there is no good way to skip over it
> > without introducing another flag. cpufreq_resume is called by
> > dpm_resume, cpufreq_suspend is called by dpm_suspend. In the failure
> > case, dpm_resume is called, but dpm_suspend is not. So on a higher level
> > it's already unbalanced.
> >
> > One possibility is to rely on the pm_transition flag. So something like:
> >
> >
> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > index dc259d20c967..8469e6fc2b2c 100644
> > --- a/drivers/base/power/main.c
> > +++ b/drivers/base/power/main.c
> > @@ -842,6 +842,7 @@ static void async_resume(void *data, async_cookie_t
> > cookie)
> >    void dpm_resume(pm_message_t state)
> >    {
> >           struct device *dev;
> > +       bool suspended = (pm_transition.event != PM_EVENT_ON);
> >           ktime_t starttime = ktime_get();
> >
> >           trace_suspend_resume(TPS("dpm_resume"), state.event, true);
> > @@ -885,7 +886,8 @@ void dpm_resume(pm_message_t state)
> >           async_synchronize_full();
> >           dpm_show_time(starttime, state, NULL);
> >
> > -       cpufreq_resume();
> > +       if (likely(suspended))
> > +               cpufreq_resume();
> >           trace_suspend_resume(TPS("dpm_resume"), state.event, false);
> >    }
>
> I was thinking about something else.
>
> Anyway, I think your original patch is OK too, but without printing the
> message.  Just combine the cpufreq_suspended check with the cpufreq_driver
> one and the unlikely() thing is not necessary.

I rather have this fixed in the dpm_suspend/resume() code. This is just 
masking the first issue that's being caused by unbalanced error 
handling. If that means adding flags in dpm_suspend/resume() then that's 
what we should do right now and clean it up later if it can be improved. 
Making cpufreq more messy doesn't seem like the right answer.

Thanks,
Saravana


--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project