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@xxxxxxxxxxxxxxxxxxx>
---
Index: usb-2.6/include/linux/pm.h
===================================================================
--- usb-2.6.orig/include/linux/pm.h
+++ usb-2.6/include/linux/pm.h
@@ -486,6 +486,7 @@ struct dev_pm_info {
unsigned int run_wake:1;
unsigned int runtime_auto:1;
unsigned int no_callbacks:1;
+ unsigned int irq_safe:1;
unsigned int use_autosuspend:1;
unsigned int timer_autosuspends:1;
enum rpm_request request;
Index: usb-2.6/include/linux/pm_runtime.h
===================================================================
--- usb-2.6.orig/include/linux/pm_runtime.h
+++ usb-2.6/include/linux/pm_runtime.h
@@ -40,6 +40,7 @@ extern int pm_generic_runtime_idle(struc
extern int pm_generic_runtime_suspend(struct device *dev);
extern int pm_generic_runtime_resume(struct device *dev);
extern void pm_runtime_no_callbacks(struct device *dev);
+extern void pm_runtime_irq_safe(struct device *dev);
extern void __pm_runtime_use_autosuspend(struct device *dev, bool use);
extern void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);
extern unsigned long pm_runtime_autosuspend_expiration(struct device *dev);
@@ -123,6 +124,7 @@ static inline int pm_generic_runtime_idl
static inline int pm_generic_runtime_suspend(struct device *dev) { return 0; }
static inline int pm_generic_runtime_resume(struct device *dev) { return 0; }
static inline void pm_runtime_no_callbacks(struct device *dev) {}
+static inline void pm_runtime_irq_safe(struct device *dev) {}
static inline void pm_runtime_mark_last_busy(struct device *dev) {}
static inline void __pm_runtime_use_autosuspend(struct device *dev,
@@ -195,6 +197,11 @@ static inline int pm_runtime_put_sync(st
return __pm_runtime_idle(dev, RPM_GET_PUT);
}
+static inline int pm_runtime_put_sync_suspend(struct device *dev)
+{
+ return __pm_runtime_suspend(dev, RPM_GET_PUT);
+}
+
static inline int pm_runtime_put_sync_autosuspend(struct device *dev)
{
return __pm_runtime_suspend(dev, RPM_GET_PUT | RPM_AUTO);
Index: usb-2.6/drivers/base/power/runtime.c
===================================================================
--- usb-2.6.orig/drivers/base/power/runtime.c
+++ usb-2.6/drivers/base/power/runtime.c
@@ -250,13 +250,16 @@ static int rpm_callback(int (*cb)(struct
if (!cb)
return -ENOSYS;
- spin_unlock_irq(&dev->power.lock);
+ if (dev->power.irq_safe) {
+ retval = cb(dev);
+ } else {
+ spin_unlock_irq(&dev->power.lock);
- retval = cb(dev);
+ retval = cb(dev);
- spin_lock_irq(&dev->power.lock);
+ spin_lock_irq(&dev->power.lock);
+ }
dev->power.runtime_error = retval;
-
return retval;
}
@@ -404,7 +407,7 @@ static int rpm_suspend(struct device *de
goto out;
}
- if (parent && !parent->power.ignore_children) {
+ if (parent && !parent->power.ignore_children && !dev->power.irq_safe) {
spin_unlock_irq(&dev->power.lock);
pm_request_idle(parent);
@@ -527,10 +530,13 @@ static int rpm_resume(struct device *dev
if (!parent && dev->parent) {
/*
- * Increment the parent's resume counter and resume it if
- * necessary.
+ * Increment the parent's usage counter and resume it if
+ * necessary. Not needed if dev is irq-safe; then the
+ * parent is permanently resumed.
*/
parent = dev->parent;
+ if (dev->power.irq_safe)
+ goto skip_parent;
spin_unlock(&dev->power.lock);
pm_runtime_get_noresume(parent);
@@ -553,6 +559,7 @@ static int rpm_resume(struct device *dev
goto out;
goto repeat;
}
+ skip_parent:
if (dev->power.no_callbacks)
goto no_callback; /* Assume success. */
@@ -584,7 +591,7 @@ static int rpm_resume(struct device *dev
rpm_idle(dev, RPM_ASYNC);
out:
- if (parent) {
+ if (parent && !dev->power.irq_safe) {
spin_unlock_irq(&dev->power.lock);
pm_runtime_put(parent);
@@ -1065,7 +1072,6 @@ EXPORT_SYMBOL_GPL(pm_runtime_allow);
* Set the power.no_callbacks flag, which tells the PM core that this
* device is power-managed through its parent and has no run-time PM
* callbacks of its own. The run-time sysfs attributes will be removed.
- *
*/
void pm_runtime_no_callbacks(struct device *dev)
{
@@ -1078,6 +1084,27 @@ void pm_runtime_no_callbacks(struct devi
EXPORT_SYMBOL_GPL(pm_runtime_no_callbacks);
/**
+ * pm_runtime_irq_safe - Leave interrupts disabled during callbacks.
+ * @dev: Device to handle
+ *
+ * Set the power.irq_safe flag, which tells the PM core that the
+ * ->runtime_suspend() and ->runtime_resume() callbacks for this device should
+ * always be invoked with the spinlock held and interrupts disabled. It also
+ * causes the parent's usage counter to be permanently incremented, preventing
+ * the parent from runtime suspending -- otherwise an irq-safe child might have
+ * to wait for a non-irq-safe parent.
+ */
+void pm_runtime_irq_safe(struct device *dev)
+{
+ if (dev->parent)
+ pm_runtime_get_sync(dev->parent);
+ spin_lock_irq(&dev->power.lock);
+ dev->power.irq_safe = 1;
+ spin_unlock_irq(&dev->power.lock);
+}
+EXPORT_SYMBOL_GPL(pm_runtime_irq_safe);
+
+/**
* update_autosuspend - Handle a change to a device's autosuspend settings.
* @dev: Device to handle.
* @old_delay: The former autosuspend_delay value.
@@ -1199,4 +1226,6 @@ void pm_runtime_remove(struct device *de
/* Change the status back to 'suspended' to match the initial status. */
if (dev->power.runtime_status == RPM_ACTIVE)
pm_runtime_set_suspended(dev);
+ if (dev->power.irq_safe && dev->parent)
+ pm_runtime_put_sync(dev->parent);
}
Index: usb-2.6/Documentation/power/runtime_pm.txt
===================================================================
--- usb-2.6.orig/Documentation/power/runtime_pm.txt
+++ usb-2.6/Documentation/power/runtime_pm.txt
@@ -50,6 +50,15 @@ type's callbacks are not defined) of giv
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
- 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
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
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