PM / core: Propagate dev->power.wakeup_path when no callbacks

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: NLoic Pallardy <loic.pallardy@st.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
[ rjw: Comment cleanup ]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/main.c

@@ -1736,6 +1736,10 @@ 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 propagate. */
+	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);