Hi Ulf and Alan, Thank you for the review. On Friday 04 March 2016 10:24:10 Alan Stern wrote: > On Fri, 4 Mar 2016, Ulf Hansson wrote: > > On 3 March 2016 at 21:16, Laurent Pinchart wrote: > >> The pm_runtime_force_suspend() and pm_runtime_force_resume() helpers are > >> designed to help driver being RPM-centric by offering an easy way to > >> manager runtime PM state during system suspend and resume. The first > >> function will force the device into runtime suspend at system suspend > >> time, while the second one will perform the reverse operation at system > >> resume time. > >> > >> However, the pm_runtime_force_resume() really forces resume, regarding > >> of whether the device was running or already suspended before the call > >> to pm_runtime_force_suspend(). This results in devices being runtime > >> resumed at system resume time when they shouldn't. > >> > >> Fix this by recording whether the device has been forcefully suspended > >> in pm_runtime_force_suspend() and condition resume in > >> pm_runtime_force_resume() to that state. > >> > >> All current users of pm_runtime_force_resume() call the function > >> uncontionally in their system resume handler (some actually set it as > >> the resume handler), all after calling pm_runtime_force_suspend() at > >> system suspend time. The change in behaviour should thus be safe. > >> > >> Signed-off-by: Laurent Pinchart > >> <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx> > >> > >> @@ -1475,6 +1476,7 @@ int pm_runtime_force_suspend(struct device *dev) > >> goto err; > >> > >> pm_runtime_set_suspended(dev); > >> + dev->power.is_force_suspended = true; > >> return 0; > >> > >> err: > >> pm_runtime_enable(dev); > >> @@ -1510,6 +1515,7 @@ int pm_runtime_force_resume(struct device *dev) > >> if (ret) > >> goto out; > >> > >> + dev->power.is_force_suspended = false; > >> pm_runtime_set_active(dev); > >> pm_runtime_mark_last_busy(dev); > >> out: > > Setting a bitflag is not SMP-safe. When you write to one of the > runtime-PM bits under dev->power, it is necessary to hold > dev->power.lock. > > > Overall I have no objections to this change, as I think it's improving > > the behaviour! > > > > What I was thinking though, but it might be a bit controversial. :-)... > > Instead of relying on whether we actually forced runtime suspend > > earlier, why couldn't we instead check the runtime PM usage count of > > the device? > > > > Only when it's greater than zero, we shall do the forced resume of the > > device, otherwise just re-enable runtime PM. > > > > This would have the affect of leaving devices in runtime suspend, > > until they really needs to be used again. It would thus decrease the > > total system PM resume time. > > > > Do you think this could work? > > If you do this then there would be no need for is_force_suspended. It > seems like a good idea to me. I agree, that's a better idea. Drivers shouldn't call pm_runtime_force_resume() if they haven't called pm_runtime_force_suspend(), so checking the PM use count should be fine. I'll modify the patch, test it and resubmit. -- Regards, Laurent Pinchart
