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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-10-16 23:05:42 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-10-16 23:05:42 +0200
commit41863fcee3039ec3de15003b78e7284c4393e862 (patch)
tree0a5019735c7c4835dd697cf8ae5aa449c341b601 /drivers/acpi/power.c
parent7d13f94ce242a9166811eb6a30a5cd712952fb04 (diff)
ACPI / power: Drop automaitc resume of power resource dependent devices
The mechanism causing devices depending on a given power resource (that is, devices that can be in D0 only if that power resource is on) to be resumed automatically when the power resource is turned on (and their "inferred" power state becomes D0 as a result) is inherently racy and in fact unnecessary. It is racy, because if the power resource is turned on and then immediately off, the device resume triggered by the first transition to "on" may still happen, causing the power resource to be turned on again. That again will trigger the "resume of dependent devices" mechanism, but if the devices in question are not in use, they will be suspended in the meantime causing the power resource to be turned off. However, the "resume of dependent devices" will next resume them again and so on. In some cases (USB port PM in particular) that leads to an endless busy loop of flipping the resource on and off continuously. It is needless, because whoever turns a power resource on will most likely turn it off at some point and the devices that go into "D0" as a result of turning it on will then go back into D3cold (generally, the state they were in before). Moreover, turning on all power resources a device needs to go into D0 is not sufficient for a full transition into D0 in general. Namely, _PS0 may need to be executed in addition to that in some cases. This means that the whole rationale of the "resume of dependent devices" mechanism was incorrect to begin with and it's best to remove it entirely. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi/power.c')
-rw-r--r--drivers/acpi/power.c100
1 files changed, 1 insertions, 99 deletions
diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
index 0c1c3ec784f..c2ad391d804 100644
--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -59,16 +59,9 @@ ACPI_MODULE_NAME("power");
#define ACPI_POWER_RESOURCE_STATE_ON 0x01
#define ACPI_POWER_RESOURCE_STATE_UNKNOWN 0xFF
-struct acpi_power_dependent_device {
- struct list_head node;
- struct acpi_device *adev;
- struct work_struct work;
-};
-
struct acpi_power_resource {
struct acpi_device device;
struct list_head list_node;
- struct list_head dependent;
char *name;
u32 system_level;
u32 order;
@@ -233,32 +226,6 @@ static int acpi_power_get_list_state(struct list_head *list, int *state)
return 0;
}
-static void acpi_power_resume_dependent(struct work_struct *work)
-{
- struct acpi_power_dependent_device *dep;
- struct acpi_device_physical_node *pn;
- struct acpi_device *adev;
- int state;
-
- dep = container_of(work, struct acpi_power_dependent_device, work);
- adev = dep->adev;
- if (acpi_power_get_inferred_state(adev, &state))
- return;
-
- if (state > ACPI_STATE_D0)
- return;
-
- mutex_lock(&adev->physical_node_lock);
-
- list_for_each_entry(pn, &adev->physical_node_list, node)
- pm_request_resume(pn->dev);
-
- list_for_each_entry(pn, &adev->power_dependent, node)
- pm_request_resume(pn->dev);
-
- mutex_unlock(&adev->physical_node_lock);
-}
-
static int __acpi_power_on(struct acpi_power_resource *resource)
{
acpi_status status = AE_OK;
@@ -283,14 +250,8 @@ static int acpi_power_on_unlocked(struct acpi_power_resource *resource)
resource->name));
} else {
result = __acpi_power_on(resource);
- if (result) {
+ if (result)
resource->ref_count--;
- } else {
- struct acpi_power_dependent_device *dep;
-
- list_for_each_entry(dep, &resource->dependent, node)
- schedule_work(&dep->work);
- }
}
return result;
}
@@ -390,52 +351,6 @@ static int acpi_power_on_list(struct list_head *list)
return result;
}
-static void acpi_power_add_dependent(struct acpi_power_resource *resource,
- struct acpi_device *adev)
-{
- struct acpi_power_dependent_device *dep;
-
- mutex_lock(&resource->resource_lock);
-
- list_for_each_entry(dep, &resource->dependent, node)
- if (dep->adev == adev)
- goto out;
-
- dep = kzalloc(sizeof(*dep), GFP_KERNEL);
- if (!dep)
- goto out;
-
- dep->adev = adev;
- INIT_WORK(&dep->work, acpi_power_resume_dependent);
- list_add_tail(&dep->node, &resource->dependent);
-
- out:
- mutex_unlock(&resource->resource_lock);
-}
-
-static void acpi_power_remove_dependent(struct acpi_power_resource *resource,
- struct acpi_device *adev)
-{
- struct acpi_power_dependent_device *dep;
- struct work_struct *work = NULL;
-
- mutex_lock(&resource->resource_lock);
-
- list_for_each_entry(dep, &resource->dependent, node)
- if (dep->adev == adev) {
- list_del(&dep->node);
- work = &dep->work;
- break;
- }
-
- mutex_unlock(&resource->resource_lock);
-
- if (work) {
- cancel_work_sync(work);
- kfree(dep);
- }
-}
-
static struct attribute *attrs[] = {
NULL,
};
@@ -524,8 +439,6 @@ static void acpi_power_expose_hide(struct acpi_device *adev,
void acpi_power_add_remove_device(struct acpi_device *adev, bool add)
{
- struct acpi_device_power_state *ps;
- struct acpi_power_resource_entry *entry;
int state;
if (adev->wakeup.flags.valid)
@@ -535,16 +448,6 @@ void acpi_power_add_remove_device(struct acpi_device *adev, bool add)
if (!adev->power.flags.power_resources)
return;
- ps = &adev->power.states[ACPI_STATE_D0];
- list_for_each_entry(entry, &ps->resources, node) {
- struct acpi_power_resource *resource = entry->resource;
-
- if (add)
- acpi_power_add_dependent(resource, adev);
- else
- acpi_power_remove_dependent(resource, adev);
- }
-
for (state = ACPI_STATE_D0; state <= ACPI_STATE_D3_HOT; state++)
acpi_power_expose_hide(adev,
&adev->power.states[state].resources,
@@ -882,7 +785,6 @@ int acpi_add_power_resource(acpi_handle handle)
acpi_init_device_object(device, handle, ACPI_BUS_TYPE_POWER,
ACPI_STA_DEFAULT);
mutex_init(&resource->resource_lock);
- INIT_LIST_HEAD(&resource->dependent);
INIT_LIST_HEAD(&resource->list_node);
resource->name = device->pnp.bus_id;
strcpy(acpi_device_name(device), ACPI_POWER_DEVICE_NAME);