PM: sleep: Adjust check before setting power.must_resume

The check before setting power.must_resume in device_suspend_noirq()
does not take power.child_count into account, but it should do that, so
use pm_runtime_need_not_resume() in it for this purpose and adjust the
comment next to it accordingly.

Fixes: 107d47b ("PM: sleep: core: Simplify the SMART_SUSPEND flag handling")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/3353728.44csPzL39Z@rjwysocki.net

Author: rafaeljw

drivers/base/power/main.c

@@ -1277,14 +1277,13 @@ static int device_suspend_noirq(struct device *dev, pm_message_t state, bool asy
 	dev->power.is_noirq_suspended = true;
 
 	/*
-	 * Skipping the resume of devices that were in use right before the
-	 * system suspend (as indicated by their PM-runtime usage counters)
-	 * would be suboptimal.  Also resume them if doing that is not allowed
-	 * to be skipped.
+	 * Devices must be resumed unless they are explicitly allowed to be left
+	 * in suspend, but even in that case skipping the resume of devices that
+	 * were in use right before the system suspend (as indicated by their
+	 * runtime PM usage counters and child counters) would be suboptimal.
 	 */
-	if (atomic_read(&dev->power.usage_count) > 1 ||
-	    !(dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME) &&
-	      dev->power.may_skip_resume))
+	if (!(dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME) &&
+	      dev->power.may_skip_resume) || !pm_runtime_need_not_resume(dev))
 		dev->power.must_resume = true;
 
 	if (dev->power.must_resume)

drivers/base/power/runtime.c

@@ -1906,7 +1906,7 @@ void pm_runtime_drop_link(struct device_link *link)
 	pm_request_idle(link->supplier);
 }
 
-static bool pm_runtime_need_not_resume(struct device *dev)
+bool pm_runtime_need_not_resume(struct device *dev)
 {
 	return atomic_read(&dev->power.usage_count) <= 1 &&
 		(atomic_read(&dev->power.child_count) == 0 ||

include/linux/pm_runtime.h

@@ -66,6 +66,7 @@ static inline bool queue_pm_work(struct work_struct *work)
 
 extern int pm_generic_runtime_suspend(struct device *dev);
 extern int pm_generic_runtime_resume(struct device *dev);
+extern bool pm_runtime_need_not_resume(struct device *dev);
 extern int pm_runtime_force_suspend(struct device *dev);
 extern int pm_runtime_force_resume(struct device *dev);
 
@@ -244,6 +245,7 @@ static inline bool queue_pm_work(struct work_struct *work) { return false; }
 
 static inline int pm_generic_runtime_suspend(struct device *dev) { return 0; }
 static inline int pm_generic_runtime_resume(struct device *dev) { return 0; }
+static inline bool pm_runtime_need_not_resume(struct device *dev) {return true; }
 static inline int pm_runtime_force_suspend(struct device *dev) { return 0; }
 static inline int pm_runtime_force_resume(struct device *dev) { return 0; }