Commit 03f14440 authored Mar 13, 2025 by Rafael J. Wysocki

PM: sleep: Fix handling devices with direct_complete set on errors

When dpm_suspend() fails, some devices with power.direct_complete set
may not have been handled by device_suspend() yet, so runtime PM has
not been disabled for them yet even though power.direct_complete is set.

Since device_resume() expects that runtime PM has been disabled for all
devices with power.direct_complete set, it will attempt to reenable
runtime PM for the devices that have not been processed by device_suspend()
which does not make sense. Had those devices had runtime PM disabled
before device_suspend() had run, device_resume() would have inadvertently
enable runtime PM for them, but this is not expected to happen because
it would require ->prepare() callbacks to return positive values for
devices with runtime PM disabled, which would be invalid.

In practice, this issue is most likely benign because pm_runtime_enable()
will not allow the "disable depth" counter to underflow, but it causes a
warning message to be printed for each affected device.

To allow device_resume() to distinguish the "direct complete" devices
that have been processed by device_suspend() from those which have not
been handled by it, make device_suspend() set power.is_suspended for
"direct complete" devices.

Next, move the power.is_suspended check in device_resume() before the
power.direct_complete check in it to make it skip the "direct complete"
devices that have not been handled by device_suspend().

This change is based on a preliminary patch from Saravana Kannan.

Fixes: aae4518b ("PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily")
Link: https://lore.kernel.org/linux-pm/20241114220921.2529905-2-saravanak@google.com/

Reported-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Saravana Kannan <saravanak@google.com>
Link: https://patch.msgid.link/12627587.O9o76ZdvQC@rjwysocki.net

parent 956af869

drivers/base/power/main.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -938,6 +938,9 @@ static void device_resume(struct device *dev, pm_message_t state, bool async)
		if (dev->power.syscore)
		goto Complete;

		if (!dev->power.is_suspended)
		goto Complete;

		if (dev->power.direct_complete) {
		/*
		* Allow new children to be added under the device after this
		@@ -963,9 +966,6 @@ static void device_resume(struct device *dev, pm_message_t state, bool async)
		*/
		dev->power.is_prepared = false;

		if (!dev->power.is_suspended)
		goto Unlock;

		if (dev->pm_domain) {
		info = "power domain ";
		callback = pm_op(&dev->pm_domain->ops, state);
		@@ -1005,7 +1005,6 @@ static void device_resume(struct device *dev, pm_message_t state, bool async)
		error = dpm_run_callback(callback, dev, state, info);
		dev->power.is_suspended = false;

		Unlock:
		device_unlock(dev);
		dpm_watchdog_clear(&wd);

		@@ -1669,6 +1668,7 @@ static int device_suspend(struct device *dev, pm_message_t state, bool async)
		pm_runtime_disable(dev);
		if (pm_runtime_status_suspended(dev)) {
		pm_dev_dbg(dev, state, "direct-complete ");
		dev->power.is_suspended = true;
		goto Complete;
		}