diff options
Diffstat (limited to 'Documentation/power/runtime_pm.txt')
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 31 |
1 files changed, 24 insertions, 7 deletions
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 6066e3a6b9a..5336149f831 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -43,13 +43,18 @@ struct dev_pm_ops { ... }; -The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks are -executed by the PM core for either the device type, or the class (if the device -type's struct dev_pm_ops object does not exist), or the bus type (if the -device type's and class' struct dev_pm_ops objects do not exist) of the given -device (this allows device types to override callbacks provided by bus types or -classes if necessary). The bus type, device type and class callbacks are -referred to as subsystem-level callbacks in what follows. +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. By default, the callbacks are always invoked in process context with interrupts enabled. However, subsystems can use the pm_runtime_irq_safe() helper function @@ -477,12 +482,14 @@ pm_runtime_autosuspend_expiration() If pm_runtime_irq_safe() has been called for a device then the following helper functions may also be used in interrupt context: +pm_runtime_idle() pm_runtime_suspend() pm_runtime_autosuspend() pm_runtime_resume() pm_runtime_get_sync() pm_runtime_put_sync() pm_runtime_put_sync_suspend() +pm_runtime_put_sync_autosuspend() 5. Runtime PM Initialization, Device Probing and Removal @@ -782,6 +789,16 @@ will behave normally, not taking the autosuspend delay into account. Similarly, if the power.use_autosuspend field isn't set then the autosuspend helper functions will behave just like the non-autosuspend counterparts. +Under some circumstances a driver or subsystem may want to prevent a device +from autosuspending immediately, even though the usage counter is zero and the +autosuspend delay time has expired. If the ->runtime_suspend() callback +returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is +in the future (as it normally would be if the callback invoked +pm_runtime_mark_last_busy()), the PM core will automatically reschedule the +autosuspend. The ->runtime_suspend() callback can't do this rescheduling +itself because no suspend requests of any kind are accepted while the device is +suspending (i.e., while the callback is running). + The implementation is well suited for asynchronous use in interrupt contexts. However such use inevitably involves races, because the PM core can't synchronize ->runtime_suspend() callbacks with the arrival of I/O requests. |