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 <loic.pallardy@xxxxxx> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx> --- 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); -- 2.17.1
