Re: [PATCH v10 1/5] PM / Runtime: Allow accessing irq_safe if no PM_RUNTIME

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Friday, November 07, 2014 09:50:58 AM Alan Stern wrote:
> On Fri, 7 Nov 2014, Krzysztof Kozlowski wrote:
> 
> > > Well, that is a good reason to introduce a wrapper around power.irq_safe in my
> > > view.
> > > 
> > > And define the wrapper so that it always returns false for CONFIG_PM_RUNTIME
> > > unset.
> > > 
> > > This way not only you wouldn't need to move the flag from under the #ifdef,
> > > but also you would make the compiler skip the relevant pieces of code
> > > entiretly for CONFIG_PM_RUNTIME unset.
> > 
> > Few days ago I would be happy with your opinion :), but know I think
> > this is better solution than wrapper. Consider case:
> > 1. PM_RUNTIME unset.
> > 2. System suspends.
> > 3. The pl330 in its suspend callback calls force_runtime_suspend which
> > leads us to amba/bus.
> > 4. The amba/bus.c in runtime suspend checks for irq_safe (it is FALSE),
> > so it disables and unprepares the clock.
> > 5. The pl330 in probe requested irq_safe so it assumes amba/bus will
> > only disable the clock. So the pl330 unprepares the clock. Again.
> 
> To me, this sounds like a good reason to avoid using 
> force_runtime_suspend().  In fact, it sounds like a good reason to 
> avoid relying on the runtime PM mechanism to handle non-runtime-PM 
> things (like a system suspend callback).  If CONFIG_PM_RUNTIME isn't 
> enabled then the runtime PM stack simply should not be used.

Amen.