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authorAlan Stern <stern@rowland.harvard.edu>2010-12-01 00:14:42 +0100
committerRafael J. Wysocki <rjw@sisk.pl>2010-12-24 15:02:41 +0100
commitc7b61de5b7b17f0df34dc7d2f8b9576f8bd36fce (patch)
treed8cf6be1aab175839973d2c76060bd41d65b2ed5 /Documentation/power/runtime_pm.txt
parent5262a47502adcfc3a64403120768f528418a3b79 (diff)
PM / Runtime: Add synchronous runtime interface for interrupt handlers (v3)
This patch (as1431c) makes the synchronous runtime-PM interface suitable for use in interrupt handlers. Subsystems can call the new pm_runtime_irq_safe() function to tell the PM core that a device's runtime_suspend and runtime_resume callbacks should be invoked with interrupts disabled and the spinlock held. This permits the pm_runtime_get_sync() and the new pm_runtime_put_sync_suspend() routines to be called from within interrupt handlers. When a device is declared irq-safe in this way, the PM core increments the parent's usage count, so the parent will never be runtime suspended. This prevents difficult situations in which an irq-safe device can't resume because it is forced to wait for its non-irq-safe parent. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'Documentation/power/runtime_pm.txt')
-rw-r--r--Documentation/power/runtime_pm.txt31
1 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 41cc7b30d7d..ffe55ffa540 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -50,6 +50,15 @@ type's callbacks are not defined) of given device. The bus type, device type
and device 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
+(->runtime_idle() is still invoked the default way). 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.
+
The subsystem-level suspend callback is _entirely_ _responsible_ for handling
the suspend of the device as appropriate, which may, but need not include
executing the device driver's own ->runtime_suspend() callback (from the
@@ -237,6 +246,10 @@ defined in include/linux/pm.h:
Section 8); it may be modified only by the pm_runtime_no_callbacks()
helper function
+ unsigned int irq_safe;
+ - indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
+ will be invoked with the spinlock held and interrupts disabled
+
unsigned int use_autosuspend;
- indicates that the device's driver supports delayed autosuspend (see
Section 9); it may be modified only by the
@@ -344,6 +357,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
- decrement the device's usage counter; if the result is 0 then run
pm_runtime_idle(dev) and return its result
+ int pm_runtime_put_sync_suspend(struct device *dev);
+ - decrement the device's usage counter; if the result is 0 then run
+ pm_runtime_suspend(dev) and return its result
+
int pm_runtime_put_sync_autosuspend(struct device *dev);
- decrement the device's usage counter; if the result is 0 then run
pm_runtime_autosuspend(dev) and return its result
@@ -397,6 +414,11 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
PM attributes from /sys/devices/.../power (or prevent them from being
added when the device is registered)
+ void pm_runtime_irq_safe(struct device *dev);
+ - set the power.irq_safe flag for the device, causing the runtime-PM
+ suspend and resume callbacks (but not the idle callback) to be invoked
+ with interrupts disabled
+
void pm_runtime_mark_last_busy(struct device *dev);
- set the power.last_busy field to the current time
@@ -438,6 +460,15 @@ pm_runtime_suspended()
pm_runtime_mark_last_busy()
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_suspend()
+pm_runtime_autosuspend()
+pm_runtime_resume()
+pm_runtime_get_sync()
+pm_runtime_put_sync_suspend()
+
5. Run-time PM Initialization, Device Probing and Removal
Initially, the run-time PM is disabled for all devices, which means that the