[PATCH 5.14 447/849] ACPI: PM: Fix sharing of wakeup power resources

Greg Kroah-Hartman
2021-11-15T23:01:57Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

[ 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>
---
drivers/acpi/power.c | 69 +++++++++++++++-----------------------------
1 file changed, 24 insertions(+), 45 deletions(-)

diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index dfe760bd7157f..e1f9a45587857 100644
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -53,7 +53,6 @@ struct acpi_power_resource {
u32 order;
unsigned int ref_count;
u8 state;
- bool wakeup_enabled;
struct mutex resource_lock;
struct list_head dependents;
};
@@ -701,7 +700,6 @@ 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)
@@ -712,26 +710,13 @@ 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.
@@ -761,39 +746,33 @@ 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:
--
2.33.0