[RFC][PATCH 2/2] PM: Make system-wide PM and runtime PM handle subsystems consistently

["Rafael J. Wysocki" <rjw@sisk.pl>]

From: Rafael J. Wysocki <rjw@sisk.pl>

The code handling system-wide power transitions (eg. suspend-to-RAM)
can in theory execute callbacks provided by the device's bus type,
device type and class in each phase of the power transition.  In
turn, the runtime PM core code only calls one of those callbacks at
a time, preferring bus type callbacks to device type or class
callbacks and device type callbacks to class callbacks.

It seems reasonable to make them both behave in the same way in that
respect.  Moreover, even though a device may belong to two subsystems
(eg. bus type and device class) simultaneously, in practice power
management callbacks for system-wide power transitions are always
provided by only one of them (ie. if the bus type callbacks are
defined, the device class ones are not and vice versa).  Thus it is
possible to modify the code handling system-wide power transitions
so that it follows the core runtime PM code (ie. treats the
subsystem callbacks as mutually exclusive).

On the other hand, the core runtime PM code will choose to execute,
for example, a runtime suspend callback provided by the device type
even if the bus type's struct dev_pm_ops object exists, but the
runtime_suspend pointer in it happens to be NULL.  This is confusing,
because it may lead to the execution of callbacks from different
subsystems during different operations (eg. the bus type suspend
callback may be executed during runtime suspend, while the device
type callback will be executed during runtime resume).

Make all of the power management code treat subsystem callbacks in
a consistent way, such that:
(1) If the device's bus type is defined (eg. dev->bus is not NULL)
    and its pm pointer is not NULL, the callbacks from dev->bus->pm
    will be used.
(2) If dev->bus is NULL or dev->bus->pm is NULL, but the device's
    device type is defined (eg. dev->type is not NULL) and its pm
    pointer is not NULL, the callbacks from dev->type->pm will be
    used.
(3) If dev->bus is NULL or dev->bus->pm is NULL and dev->type is
    NULL or dev->type->pm is NULL, the callbacks from dev->class->pm
    will be used provided that both dev->class and dev->class->pm
    are not NULL.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 Documentation/power/devices.txt |   28 +++----
 drivers/base/power/main.c       |  141 +++++++++++++++++-----------------------
 drivers/base/power/runtime.c    |   12 +--
 3 files changed, 79 insertions(+), 102 deletions(-)

Index: linux-2.6/drivers/base/power/main.c
===================================================================
--- linux-2.6.orig/drivers/base/power/main.c
+++ linux-2.6/drivers/base/power/main.c
@@ -433,21 +433,17 @@ static int device_resume_noirq(struct de
 		error = pm_noirq_op(dev, dev->bus->pm, state);
 		if (error)
 			goto End;
-	}
-
-	if (dev->type && dev->type->pm) {
+	} else if (dev->type && dev->type->pm) {
 		pm_dev_dbg(dev, state, "EARLY type ");
 		error = pm_noirq_op(dev, dev->type->pm, state);
 		if (error)
 			goto End;
-	}
-
-	if (dev->class && dev->class->pm) {
+	} else if (dev->class && dev->class->pm) {
 		pm_dev_dbg(dev, state, "EARLY class ");
 		error = pm_noirq_op(dev, dev->class->pm, state);
 	}
 
-End:
+ End:
 	TRACE_RESUME(error);
 	return error;
 }
@@ -532,21 +528,18 @@ static int device_resume(struct device *
 		if (dev->bus->pm) {
 			pm_dev_dbg(dev, state, "");
 			error = pm_op(dev, dev->bus->pm, state);
+			goto End;
 		} else if (dev->bus->resume) {
 			pm_dev_dbg(dev, state, "legacy ");
 			error = legacy_resume(dev, dev->bus->resume);
-		}
-		if (error)
 			goto End;
+		}
 	}
 
-	if (dev->type) {
-		if (dev->type->pm) {
-			pm_dev_dbg(dev, state, "type ");
-			error = pm_op(dev, dev->type->pm, state);
-		}
-		if (error)
-			goto End;
+	if (dev->type && dev->type->pm) {
+		pm_dev_dbg(dev, state, "type ");
+		error = pm_op(dev, dev->type->pm, state);
+		goto End;
 	}
 
 	if (dev->class) {
@@ -558,6 +551,7 @@ static int device_resume(struct device *
 			error = legacy_resume(dev, dev->class->resume);
 		}
 	}
+
  End:
 	device_unlock(dev);
 	complete_all(&dev->power.completion);
@@ -644,19 +638,18 @@ static void device_complete(struct devic
 		dev->pwr_domain->ops.complete(dev);
 	}
 
-	if (dev->class && dev->class->pm && dev->class->pm->complete) {
-		pm_dev_dbg(dev, state, "completing class ");
-		dev->class->pm->complete(dev);
-	}
-
-	if (dev->type && dev->type->pm && dev->type->pm->complete) {
-		pm_dev_dbg(dev, state, "completing type ");
-		dev->type->pm->complete(dev);
-	}
-
-	if (dev->bus && dev->bus->pm && dev->bus->pm->complete) {
+	if (dev->bus && dev->bus->pm) {
 		pm_dev_dbg(dev, state, "completing ");
-		dev->bus->pm->complete(dev);
+		if (dev->bus->pm->complete)
+			dev->bus->pm->complete(dev);
+	} else if (dev->type && dev->type->pm) {
+		pm_dev_dbg(dev, state, "completing type ");
+		if (dev->type->pm->complete)
+			dev->type->pm->complete(dev);
+	} else if (dev->class && dev->class->pm) {
+		pm_dev_dbg(dev, state, "completing class ");
+		if (dev->class->pm->complete)
+			dev->class->pm->complete(dev);
 	}
 
 	device_unlock(dev);
@@ -741,27 +734,23 @@ static pm_message_t resume_event(pm_mess
  */
 static int device_suspend_noirq(struct device *dev, pm_message_t state)
 {
-	int error = 0;
+	int error;
 
-	if (dev->class && dev->class->pm) {
-		pm_dev_dbg(dev, state, "LATE class ");
-		error = pm_noirq_op(dev, dev->class->pm, state);
+	if (dev->bus && dev->bus->pm) {
+		pm_dev_dbg(dev, state, "LATE ");
+		error = pm_noirq_op(dev, dev->bus->pm, state);
 		if (error)
-			goto End;
-	}
-
-	if (dev->type && dev->type->pm) {
+			return error;
+	} else if (dev->type && dev->type->pm) {
 		pm_dev_dbg(dev, state, "LATE type ");
 		error = pm_noirq_op(dev, dev->type->pm, state);
 		if (error)
-			goto End;
-	}
-
-	if (dev->bus && dev->bus->pm) {
-		pm_dev_dbg(dev, state, "LATE ");
-		error = pm_noirq_op(dev, dev->bus->pm, state);
+			return error;
+	} else if (dev->class && dev->class->pm) {
+		pm_dev_dbg(dev, state, "LATE class ");
+		error = pm_noirq_op(dev, dev->class->pm, state);
 		if (error)
-			goto End;
+			return error;
 	}
 
 	if (dev->pwr_domain) {
@@ -769,8 +758,7 @@ static int device_suspend_noirq(struct d
 		pm_noirq_op(dev, &dev->pwr_domain->ops, state);
 	}
 
-End:
-	return error;
+	return 0;
 }
 
 /**
@@ -857,40 +845,36 @@ static int __device_suspend(struct devic
 		goto End;
 	}
 
-	if (dev->class) {
-		if (dev->class->pm) {
-			pm_dev_dbg(dev, state, "class ");
-			error = pm_op(dev, dev->class->pm, state);
-		} else if (dev->class->suspend) {
-			pm_dev_dbg(dev, state, "legacy class ");
-			error = legacy_suspend(dev, state, dev->class->suspend);
-		}
-		if (error)
-			goto End;
-	}
-
-	if (dev->type) {
-		if (dev->type->pm) {
-			pm_dev_dbg(dev, state, "type ");
-			error = pm_op(dev, dev->type->pm, state);
-		}
-		if (error)
-			goto End;
-	}
-
 	if (dev->bus) {
 		if (dev->bus->pm) {
 			pm_dev_dbg(dev, state, "");
 			error = pm_op(dev, dev->bus->pm, state);
+			goto Domain;
 		} else if (dev->bus->suspend) {
 			pm_dev_dbg(dev, state, "legacy ");
 			error = legacy_suspend(dev, state, dev->bus->suspend);
+			goto Domain;
 		}
-		if (error)
-			goto End;
 	}
 
-	if (dev->pwr_domain) {
+	if (dev->type && dev->type->pm) {
+		pm_dev_dbg(dev, state, "type ");
+		error = pm_op(dev, dev->type->pm, state);
+		goto Domain;
+	}
+
+	if (dev->class) {
+		if (dev->class->pm) {
+			pm_dev_dbg(dev, state, "class ");
+			error = pm_op(dev, dev->class->pm, state);
+		} else if (dev->class->suspend) {
+			pm_dev_dbg(dev, state, "legacy class ");
+			error = legacy_suspend(dev, state, dev->class->suspend);
+		}
+	}
+
+ Domain:
+	if (!error && dev->pwr_domain) {
 		pm_dev_dbg(dev, state, "power domain ");
 		pm_op(dev, &dev->pwr_domain->ops, state);
 	}
@@ -985,25 +969,24 @@ static int device_prepare(struct device
 
 	device_lock(dev);
 
-	if (dev->bus && dev->bus->pm && dev->bus->pm->prepare) {
+	if (dev->bus && dev->bus->pm) {
 		pm_dev_dbg(dev, state, "preparing ");
-		error = dev->bus->pm->prepare(dev);
+		if (dev->bus->pm->prepare)
+			error = dev->bus->pm->prepare(dev);
 		suspend_report_result(dev->bus->pm->prepare, error);
 		if (error)
 			goto End;
-	}
-
-	if (dev->type && dev->type->pm && dev->type->pm->prepare) {
+	} else if (dev->type && dev->type->pm) {
 		pm_dev_dbg(dev, state, "preparing type ");
-		error = dev->type->pm->prepare(dev);
+		if (dev->type->pm->prepare)
+			error = dev->type->pm->prepare(dev);
 		suspend_report_result(dev->type->pm->prepare, error);
 		if (error)
 			goto End;
-	}
-
-	if (dev->class && dev->class->pm && dev->class->pm->prepare) {
+	} else if (dev->class && dev->class->pm) {
 		pm_dev_dbg(dev, state, "preparing class ");
-		error = dev->class->pm->prepare(dev);
+		if (dev->class->pm->prepare)
+			error = dev->class->pm->prepare(dev);
 		suspend_report_result(dev->class->pm->prepare, error);
 		if (error)
 			goto End;
Index: linux-2.6/drivers/base/power/runtime.c
===================================================================
--- linux-2.6.orig/drivers/base/power/runtime.c
+++ linux-2.6/drivers/base/power/runtime.c
@@ -214,9 +214,9 @@ static int rpm_idle(struct device *dev,
 
 	dev->power.idle_notification = true;
 
-	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_idle)
+	if (dev->bus && dev->bus->pm)
 		callback = dev->bus->pm->runtime_idle;
-	else if (dev->type && dev->type->pm && dev->type->pm->runtime_idle)
+	else if (dev->type && dev->type->pm)
 		callback = dev->type->pm->runtime_idle;
 	else if (dev->class && dev->class->pm)
 		callback = dev->class->pm->runtime_idle;
@@ -382,9 +382,9 @@ static int rpm_suspend(struct device *de
 
 	__update_runtime_status(dev, RPM_SUSPENDING);
 
-	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_suspend)
+	if (dev->bus && dev->bus->pm)
 		callback = dev->bus->pm->runtime_suspend;
-	else if (dev->type && dev->type->pm && dev->type->pm->runtime_suspend)
+	else if (dev->type && dev->type->pm)
 		callback = dev->type->pm->runtime_suspend;
 	else if (dev->class && dev->class->pm)
 		callback = dev->class->pm->runtime_suspend;
@@ -584,9 +584,9 @@ static int rpm_resume(struct device *dev
 	if (dev->pwr_domain)
 		rpm_callback(dev->pwr_domain->ops.runtime_resume, dev);
 
-	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_resume)
+	if (dev->bus && dev->bus->pm)
 		callback = dev->bus->pm->runtime_resume;
-	else if (dev->type && dev->type->pm && dev->type->pm->runtime_resume)
+	else if (dev->type && dev->type->pm)
 		callback = dev->type->pm->runtime_resume;
 	else if (dev->class && dev->class->pm)
 		callback = dev->class->pm->runtime_resume;
Index: linux-2.6/Documentation/power/devices.txt
===================================================================
--- linux-2.6.orig/Documentation/power/devices.txt
+++ linux-2.6/Documentation/power/devices.txt
@@ -249,23 +249,17 @@ various phases always run after tasks ha
 unfrozen.  Furthermore, the *_noirq phases run at a time when IRQ handlers have
 been disabled (except for those marked with the IRQ_WAKEUP flag).
 
-Most phases use bus, type, and class callbacks (that is, methods defined in
-dev->bus->pm, dev->type->pm, and dev->class->pm).  The prepare and complete
-phases are exceptions; they use only bus callbacks.  When multiple callbacks
-are used in a phase, they are invoked in the order: <class, type, bus> during
-power-down transitions and in the opposite order during power-up transitions.
-For example, during the suspend phase the PM core invokes
-
-	dev->class->pm.suspend(dev);
-	dev->type->pm.suspend(dev);
-	dev->bus->pm.suspend(dev);
-
-before moving on to the next device, whereas during the resume phase the core
-invokes
-
-	dev->bus->pm.resume(dev);
-	dev->type->pm.resume(dev);
-	dev->class->pm.resume(dev);
+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 bus provides a struct dev_pm_ops object pointed to by its
+pm field (i.e. both dev->bus and dev->bus->pm are defined), the callbacks
+included in that object (i.e. dev->bus->pm) will be used.  In turn, 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 PM core will used the
+callbacks from that object (i.e. dev->type->pm).  Finally, if the pm fields of
+both the bus and device type objects are NULL (or those objects do not exist),
+the callbacks provided by the class (that is, the callbacks from dev->class->pm)
+will be used.
 
 These callbacks may in turn invoke device- or driver-specific methods stored in
 dev->driver->pm, but they don't have to.