diff options
| -rw-r--r-- | Documentation/power/devices.txt | 42 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 29 |
2 files changed, 45 insertions, 26 deletions
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt index 646a89e0c07..4342acbeee1 100644 --- a/Documentation/power/devices.txt +++ b/Documentation/power/devices.txt @@ -123,9 +123,10 @@ please refer directly to the source code for more information about it. Subsystem-Level Methods ----------------------- The core methods to suspend and resume devices reside in struct dev_pm_ops -pointed to by the pm member of struct bus_type, struct device_type and -struct class. They are mostly of interest to the people writing infrastructure -for buses, like PCI or USB, or device type and device class drivers. +pointed to by the ops member of struct dev_pm_domain, or by the pm member of +struct bus_type, struct device_type and struct class. They are mostly of +interest to the people writing infrastructure for platforms and buses, like PCI +or USB, or device type and device class drivers. Bus drivers implement these methods as appropriate for the hardware and the drivers using it; PCI works differently from USB, and so on. Not many people @@ -251,18 +252,29 @@ various phases always run after tasks have been frozen and before they are unfrozen. Furthermore, the *_noirq phases run at a time when IRQ handlers have been disabled (except for those marked with the IRQ_WAKEUP flag). -All phases use bus, type, or class callbacks (that is, methods defined in -dev->bus->pm, dev->type->pm, or dev->class->pm). These callbacks are mutually -exclusive, so if the device type provides a struct dev_pm_ops object pointed to -by its pm field (i.e. both dev->type and dev->type->pm are defined), the -callbacks included in that object (i.e. dev->type->pm) will be used. Otherwise, -if the class provides a struct dev_pm_ops object pointed to by its pm field -(i.e. both dev->class and dev->class->pm are defined), the PM core will use the -callbacks from that object (i.e. dev->class->pm). Finally, if the pm fields of -both the device type and class objects are NULL (or those objects do not exist), -the callbacks provided by the bus (that is, the callbacks from dev->bus->pm) -will be used (this allows device types to override callbacks provided by bus -types or classes if necessary). +All phases use PM domain, bus, type, or class callbacks (that is, methods +defined in dev->pm_domain->ops, dev->bus->pm, dev->type->pm, or dev->class->pm). +These callbacks are regarded by the PM core as mutually exclusive. Moreover, +PM domain callbacks always take precedence over bus, type and class callbacks, +while type callbacks take precedence over bus and class callbacks, and class +callbacks take precedence over bus callbacks. To be precise, the following +rules are used to determine which callback to execute in the given phase: + + 1. If dev->pm_domain is present, the PM core will attempt to execute the + callback included in dev->pm_domain->ops. If that callback is not + present, no action will be carried out for the given device. + + 2. Otherwise, if both dev->type and dev->type->pm are present, the callback + included in dev->type->pm will be executed. + + 3. Otherwise, if both dev->class and dev->class->pm are present, the + callback included in dev->class->pm will be executed. + + 4. Otherwise, if both dev->bus and dev->bus->pm are present, the callback + included in dev->bus->pm will be executed. + +This allows PM domains and device types to override callbacks provided by bus +types or device classes if necessary. These callbacks may in turn invoke device- or driver-specific methods stored in dev->driver->pm, but they don't have to. diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 5336149f831..79b10a090c9 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -44,17 +44,24 @@ 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 |