[PATCH v2 2/3] ACPI: PM: Fix sharing of wakeup power resources
From: Rafael J. Wysocki <hidden>
Date: 2021-10-16 10:11:14
Also in:
linux-acpi, linux-pci, lkml
From: Rafael J. Wysocki <redacted>
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 <redacted>
---
v1 -> v2:
* Restore the initialization of err in two places removed by v1 by mistake.
---
drivers/acpi/power.c | 69 +++++++++++++++++----------------------------------
1 file changed, 24 insertions(+), 45 deletions(-)
Index: linux-pm/drivers/acpi/power.c
===================================================================--- linux-pm.orig/drivers/acpi/power.c
+++ linux-pm/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_d */ 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(stru 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(str 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: