Commit a2d7b2e0 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

ACPI: PM: Fix sharing of wakeup power resources 



If an ACPI wakeup power resource is shared between multiple devices,
it may not be managed correctly.

Suppose, for example, that two devices, A and B, share a wakeup power
resource P whose wakeup_enabled flag is 0 initially.  Next, suppose
that wakeup power is enabled for A and B, in this order, and disabled
for B.  When wakeup power is enabled for A, P will be turned on and
its wakeup_enabled flag will be set.  Next, when wakeup power is
enabled for B, P will not be touched, because its wakeup_enabled flag
is set.  Now, when wakeup power is disabled for B, P will be turned
off which is incorrect, because A will still need P in order to signal
wakeup.

Moreover, if wakeup power is enabled for A and then disabled for B,
the latter will cause P to be turned off incorrectly (it will be still
needed by A), because acpi_disable_wakeup_device_power() is allowed
to manipulate power resources when the wakeup.prepare_count counter
of the given device is 0.

While the first issue could be addressed by changing the
wakeup_enabled power resource flag into a counter, addressing the
second one requires modifying acpi_disable_wakeup_device_power() to
do nothing when the target device's wakeup.prepare_count reference
counter is zero and that would cause the new counter to be redundant.
Namely, if acpi_disable_wakeup_device_power() is modified as per the
above, every change of the new counter following a wakeup.prepare_count
change would be reflected by the analogous change of the main reference
counter of the given power resource.

Accordingly, modify acpi_disable_wakeup_device_power() to do nothing
when the target device's wakeup.prepare_count reference counter is
zero and drop the power resource wakeup_enabled flag altogether.

While at it, ensure that all of the power resources that can be
turned off will be turned off when disabling device wakeup due to
a power resource manipulation error, to prevent energy from being
wasted.

Fixes: b5d667eb ("ACPI / PM: Take unusual configurations of power resources into account")
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7a63296d

drivers/acpi/power.c

+24 −45
Original line number Diff line number Diff line
@@ -52,7 +52,6 @@ struct acpi_power_resource { 
	u32 order;

	unsigned int ref_count;

	u8 state;

	bool wakeup_enabled;

	struct mutex resource_lock;

	struct list_head dependents;

};
@@ -710,7 +709,6 @@ int acpi_device_sleep_wake(struct acpi_device *dev, 
 */

int acpi_enable_wakeup_device_power(struct acpi_device *dev, int sleep_state)

{

	struct acpi_power_resource_entry *entry;

	int err = 0;



	if (!dev || !dev->wakeup.flags.valid)
@@ -721,26 +719,13 @@ int acpi_enable_wakeup_device_power(struct acpi_device *dev, int sleep_state) 
	if (dev->wakeup.prepare_count++)

		goto out;



	list_for_each_entry(entry, &dev->wakeup.resources, node) {

		struct acpi_power_resource *resource = entry->resource;



		mutex_lock(&resource->resource_lock);



		if (!resource->wakeup_enabled) {

			err = acpi_power_on_unlocked(resource);

			if (!err)

				resource->wakeup_enabled = true;

		}



		mutex_unlock(&resource->resource_lock);



	err = acpi_power_on_list(&dev->wakeup.resources);

	if (err) {

			dev_err(&dev->dev,

				"Cannot turn wakeup power resources on\n");

		dev_err(&dev->dev, "Cannot turn on wakeup power resources\n");

		dev->wakeup.flags.valid = 0;

		goto out;

	}

	}



	/*

	 * Passing 3 as the third argument below means the device may be

	 * put into arbitrary power state afterward.
@@ -770,39 +755,33 @@ int acpi_disable_wakeup_device_power(struct acpi_device *dev) 


	mutex_lock(&acpi_device_lock);



	if (--dev->wakeup.prepare_count > 0)

	if (dev->wakeup.prepare_count > 1) {

		dev->wakeup.prepare_count--;

		goto out;

	}



	/*

	 * Executing the code below even if prepare_count is already zero when

	 * the function is called may be useful, for example for initialisation.

	 */

	if (dev->wakeup.prepare_count < 0)

		dev->wakeup.prepare_count = 0;

	/* Do nothing if wakeup power has not been enabled for this device. */

	if (!dev->wakeup.prepare_count)

		goto out;



	err = acpi_device_sleep_wake(dev, 0, 0, 0);

	if (err)

		goto out;



	/*

	 * All of the power resources in the list need to be turned off even if

	 * there are errors.

	 */

	list_for_each_entry(entry, &dev->wakeup.resources, node) {

		struct acpi_power_resource *resource = entry->resource;



		mutex_lock(&resource->resource_lock);

		int ret;



		if (resource->wakeup_enabled) {

			err = acpi_power_off_unlocked(resource);

			if (!err)

				resource->wakeup_enabled = false;

		ret = acpi_power_off(entry->resource);

		if (ret && !err)

			err = ret;

	}



		mutex_unlock(&resource->resource_lock);



	if (err) {

			dev_err(&dev->dev,

				"Cannot turn wakeup power resources off\n");

		dev_err(&dev->dev, "Cannot turn off wakeup power resources\n");

		dev->wakeup.flags.valid = 0;

			break;

		}

	}



 out: