On Wednesday, April 10, 2019 11:55:16 AM CEST Ulf Hansson wrote: > The dev->power.direct_complete flag may become set in device_prepare() in > case the device don't have any PM callbacks (dev->power.no_pm_callbacks is > set). This leads to a broken behaviour, when there is child having wakeup > enabled and relies on its parent to be used in the wakeup path. > > More precisely, when the direct complete path becomes selected for the > child in __device_suspend(), the propagation of the dev->power.wakeup_path > becomes skipped as well. > > Let's address this problem, by checking if the device is a part the wakeup > path or has wakeup enabled, then prevent the direct complete path from > being used. > > Reported-by: Loic Pallardy <[email protected]> > Signed-off-by: Ulf Hansson <[email protected]> > --- > > More background: > > This problem was reported by Loic Pallardy, offlist, while he was working > on enabling wakeup for a tty serial console driver. > > When I looked more closely, I noticed that uart_suspend_port() calls > device_may_wakeup() for the tty child devices, and then also the used serial > driver check its device (parent) for device_may_wakeup(). To me this looks > like > workarounds to fix a behaviour that really should be dealt with from the PM > core, no matter of whether the child have PM callbacks assigned or not. > > In other words, it seems like the serial driver(s) should be checking the > wakeup_path flag for the parent, solely, instead. > > I haven't digested further behaviours for other subsystem, but recently > reviewed a patch for a gpio driver [1], that seems to be suffering from the > similar problems. > > Kind regards > Ulf Hansson > > [1] > https://lkml.org/lkml/2019/4/4/1283 > > --- > drivers/base/power/main.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index 41eba82ee7b9..f9cfdeee8288 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -1747,6 +1747,10 @@ static int __device_suspend(struct device *dev, > pm_message_t state, bool async) > if (dev->power.syscore) > goto Complete; > > + /* Avoid direct_complete, to let wakeup_path being propagated. */ > + if (device_may_wakeup(dev) || dev->power.wakeup_path) > + dev->power.direct_complete = false; > + > if (dev->power.direct_complete) { > if (pm_runtime_status_suspended(dev)) { > pm_runtime_disable(dev); >
Applied, thanks!
