ACPI: PM: Fix sharing of wakeup power resources

[ Upstream commit a2d7b2e004af6b09f21ac3d10f8f4456c16a8ddf ]

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: b5d667eb392e ("ACPI / PM: Take unusual configurations of power resources into account")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index 3d34cee..4b42deb 100644 (file)
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -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);
-
-               if (err) {
-                       dev_err(&dev->dev,
-                               "Cannot turn wakeup power resources on\n");
-                       dev->wakeup.flags.valid = 0;
-                       goto out;
-               }
+       err = acpi_power_on_list(&dev->wakeup.resources);
+       if (err) {
+               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);
-
-               if (resource->wakeup_enabled) {
-                       err = acpi_power_off_unlocked(resource);
-                       if (!err)
-                               resource->wakeup_enabled = false;
-               }
-
-               mutex_unlock(&resource->resource_lock);
+               int ret;
 
-               if (err) {
-                       dev_err(&dev->dev,
-                               "Cannot turn wakeup power resources off\n");
-                       dev->wakeup.flags.valid = 0;
-                       break;
-               }
+               ret = acpi_power_off(entry->resource);
+               if (ret && !err)
+                       err = ret;
+       }
+       if (err) {
+               dev_err(&dev->dev, "Cannot turn off wakeup power resources\n");
+               dev->wakeup.flags.valid = 0;
        }
 
  out: