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ACPI: PM: Fix sharing of wakeup power resources

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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: b5d667eb39 ("ACPI / PM: Take unusual configurations of power resources into account")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Rafael J. Wysocki 2021-10-16 12:11:08 +02:00
parent 7a63296d6f
commit a2d7b2e004
1 changed files with 24 additions and 45 deletions
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69
drivers/acpi/power.c
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@ -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;
int ret;
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);
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: