diff options
Diffstat (limited to 'Documentation/power/runtime_pm.txt')
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 40 |
1 files changed, 24 insertions, 16 deletions
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 5336149f831..c2ae8bf77d4 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -44,25 +44,33 @@ struct dev_pm_ops { }; The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks -are executed by the PM core for either the power domain, or the device type -(if the device power domain's struct dev_pm_ops does not exist), or the class -(if the device power domain's and type's struct dev_pm_ops object does not -exist), or the bus type (if the device power domain's, type's and class' -struct dev_pm_ops objects do not exist) of the given device, so the priority -order of callbacks from high to low is that power domain callbacks, device -type callbacks, class callbacks and bus type callbacks, and the high priority -one will take precedence over low priority one. The bus type, device type and -class callbacks are referred to as subsystem-level callbacks in what follows, -and generally speaking, the power domain callbacks are used for representing -power domains within a SoC. +are executed by the PM core for the device's subsystem that may be either of +the following: + + 1. PM domain of the device, if the device's PM domain object, dev->pm_domain, + is present. + + 2. Device type of the device, if both dev->type and dev->type->pm are present. + + 3. Device class of the device, if both dev->class and dev->class->pm are + present. + + 4. Bus type of the device, if both dev->bus and dev->bus->pm are present. + +The PM core always checks which callback to use in the order given above, so the +priority order of callbacks from high to low is: PM domain, device type, class +and bus type. Moreover, the high-priority one will always take precedence over +a low-priority one. The PM domain, bus type, device type and class callbacks +are referred to as subsystem-level callbacks in what follows. By default, the callbacks are always invoked in process context with interrupts enabled. However, subsystems can use the pm_runtime_irq_safe() helper function -to tell the PM core that a device's ->runtime_suspend() and ->runtime_resume() -callbacks should be invoked in atomic context with interrupts disabled. -This implies that these callback routines must not block or sleep, but it also -means that the synchronous helper functions listed at the end of Section 4 can -be used within an interrupt handler or in an atomic context. +to tell the PM core that their ->runtime_suspend(), ->runtime_resume() and +->runtime_idle() callbacks may be invoked in atomic context with interrupts +disabled for a given device. This implies that the callback routines in +question must not block or sleep, but it also means that the synchronous helper +functions listed at the end of Section 4 may be used for that device within an +interrupt handler or generally in an atomic context. The subsystem-level suspend callback is _entirely_ _responsible_ for handling the suspend of the device as appropriate, which may, but need not include |