Re: [Resend][PATCH] PM: Move disabling/enabling runtime PM to late suspend/early resume

From: Rafael J. Wysocki
Date: Fri Dec 21 2012 - 17:04:31 EST

On Friday, December 21, 2012 11:52:56 AM Kevin Hilman wrote:
> "Rafael J. Wysocki" <rjw@xxxxxxx> writes:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > Currently, the PM core disables runtime PM for all devices right
> > after executing subsystem/driver .suspend() callbacks for them
> > and re-enables it right before executing subsystem/driver .resume()
> > callbacks for them. This may lead to problems when there are
> > two devices such that the .suspend() callback executed for one of
> > them depends on runtime PM working for the other. In that case,
> > if runtime PM has already been disabled for the second device,
> > the first one's .suspend() won't work correctly (and analogously
> > for resume).
> >
> > To make those issues go away, make the PM core disable runtime PM
> > for devices right before executing subsystem/driver .suspend_late()
> > callbacks for them and enable runtime PM for them right after
> > executing subsystem/driver .resume_early() callbacks for them. This
> > way the potential conflitcs between .suspend_late()/.resume_early()
> > and their runtime PM counterparts are still prevented from happening,
> > but the subtle ordering issues related to disabling/enabling runtime
> > PM for devices during system suspend/resume are much easier to avoid.
> >
> > Reported-and-tested-by: Jan-Matthias Braun <jan_braun@xxxxxxx>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Yes!
> Of course if there are dependencies between drivers late/early
> callbacks, we'll still have the same problems, but those should be
> *very* rare compared to the suspend/resume dependencies.

Well, let's put it this way: Any dependencies between drivers' late/early
callbacks that make things break because runtime PM is disabled at that time
are bugs that need to be fixed.


Because runtime PM has always been disabled during late/early callbacks since
they were introduced and if somebody conveniently ignored that, then this is
this person's problem entirely.

> I haven't been able to do any testing with this yet (I'm away from my
> hardware for a bit), but I totally support this change.
> Reviewed-by: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>



I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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