On Fri, 4 Mar 2016, Ulf Hansson wrote: > + Alan > > On 3 March 2016 at 21:16, Laurent Pinchart > <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx> 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. Alan Stern
