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authorRafael J. Wysocki <rjw@sisk.pl>2011-11-23 21:18:39 +0100
committerRafael J. Wysocki <rjw@sisk.pl>2011-11-28 22:14:19 +0100
commit5841eb6402707a387b216373e65c9c28e8136663 (patch)
tree1841f84c931e6e55ab510f4d44c505e802eae4eb /Documentation
parentbb58dd5d1ffad6c2d21c69698ba766dad4ae54e6 (diff)
downloadvexpress-lsk-5841eb6402707a387b216373e65c9c28e8136663.tar.gz
PM / Domains: Document how PM domains are used by the PM core
The current power management documentation in Documentation/power/ either doesn't cover PM domains at all, or gives inaccurate information about them, so update the relevant files in there to follow the code. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/power/devices.txt42
-rw-r--r--Documentation/power/runtime_pm.txt29
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