[PATCH v8 3/4] PM / sleep: Go direct_complete if driver has no callbacks

[Tomeu Vizoso]

If a suitable prepare callback cannot be found for a given device and
its driver has no PM callbacks at all, assume that it can go direct to
complete when the system goes to sleep.

The reason for this is that there's lots of devices in a system that do
no PM at all and there's no reason for them to prevent their ancestors
to do direct_complete if they can support it.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
---

Changes in v8:
- Move no_pm_callbacks field into CONFIG_PM_SLEEP
- Call device_check_pm_callbacks only after a device is bound or unbound

Changes in v7:
- Reduce indentation by adding a label in device_prepare()

Changes in v6:
- Add stub for !CONFIG_PM.
- Move implementation of device_check_pm_callbacks to power/main.c as it
  doesn't belong to CONFIG_PM_SLEEP.
- Take dev->power.lock before modifying flag.

Changes in v5:
- Check for all dev_pm_ops instances associated to a device, updating a
  no_pm_callbacks flag at the times when that could change.

 drivers/base/dd.c           |  3 +++
 drivers/base/power/domain.c |  2 ++
 drivers/base/power/main.c   | 33 +++++++++++++++++++++++++++++++++
 drivers/base/power/power.h  |  6 ++++++
 include/linux/pm.h          |  1 +
 5 files changed, 45 insertions(+)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index f2007fa7316f..2e3809affb06 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -210,6 +210,8 @@ static void driver_bound(struct device *dev)
 
 	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 
+	device_check_pm_callbacks(dev);
+
 	/*
 	 * Make sure the device is no longer in one of the deferred lists and
 	 * kick off retrying all pending devices
@@ -700,6 +702,7 @@ static void __device_release_driver(struct device *dev)
 			dev->pm_domain->dismiss(dev);
 
 		klist_remove(&dev->p->knode_driver);
+		device_check_pm_callbacks(dev);
 		if (dev->bus)
 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 						     BUS_NOTIFY_UNBOUND_DRIVER,
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index b75d02aa8d93..9dc1ce9c573b 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -20,6 +20,8 @@
 #include <linux/suspend.h>
 #include <linux/export.h>
 
+#include "power.h"
+
 #define GENPD_RETRY_MAX_MS	250		/* Approximate */
 
 #define GENPD_DEV_CALLBACK(genpd, type, callback, dev)		\
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 1710c26ba097..43b44f8251c7 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1569,6 +1569,11 @@ static int device_prepare(struct device *dev, pm_message_t state)
 
 	dev->power.wakeup_path = device_may_wakeup(dev);
 
+	if (dev->power.no_pm_callbacks) {
+		ret = 1;	/* Let device go direct_complete */
+		goto unlock;
+	}
+
 	if (dev->pm_domain) {
 		info = "preparing power domain ";
 		callback = dev->pm_domain->ops.prepare;
@@ -1591,6 +1596,7 @@ static int device_prepare(struct device *dev, pm_message_t state)
 	if (callback)
 		ret = callback(dev);
 
+unlock:
 	device_unlock(dev);
 
 	if (ret < 0) {
@@ -1719,3 +1725,30 @@ void dpm_for_each_dev(void *data, void (*fn)(struct device *, void *))
 	device_pm_unlock();
 }
 EXPORT_SYMBOL_GPL(dpm_for_each_dev);
+
+static bool pm_ops_is_empty(const struct dev_pm_ops *ops)
+{
+	if (!ops)
+		return true;
+
+	return !ops->prepare &&
+	       !ops->suspend &&
+	       !ops->suspend_late &&
+	       !ops->suspend_noirq &&
+	       !ops->resume_noirq &&
+	       !ops->resume_early &&
+	       !ops->resume &&
+	       !ops->complete;
+}
+
+void device_check_pm_callbacks(struct device *dev)
+{
+	spin_lock_irq(&dev->power.lock);
+	dev->power.no_pm_callbacks =
+		(!dev->bus || pm_ops_is_empty(dev->bus->pm)) &&
+		(!dev->class || pm_ops_is_empty(dev->class->pm)) &&
+		(!dev->type || pm_ops_is_empty(dev->type->pm)) &&
+		(!dev->pm_domain || pm_ops_is_empty(&dev->pm_domain->ops)) &&
+		(!dev->driver || pm_ops_is_empty(dev->driver->pm));
+	spin_unlock_irq(&dev->power.lock);
+}
diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h
index 998fa6b23084..b3e35e825cd8 100644
--- a/drivers/base/power/power.h
+++ b/drivers/base/power/power.h
@@ -37,6 +37,8 @@ extern void device_wakeup_detach_irq(struct device *dev);
 extern void device_wakeup_arm_wake_irqs(void);
 extern void device_wakeup_disarm_wake_irqs(void);
 
+extern void device_check_pm_callbacks(struct device *dev);
+
 #else
 
 static inline int
@@ -58,6 +60,10 @@ static inline void device_wakeup_disarm_wake_irqs(void)
 {
 }
 
+static inline void device_check_pm_callbacks(struct device *dev)
+{
+}
+
 #endif /* CONFIG_PM_SLEEP */
 
 /*
diff --git a/include/linux/pm.h b/include/linux/pm.h
index 35d599e7250d..7943acb74ae4 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -573,6 +573,7 @@ struct dev_pm_info {
 	struct wakeup_source	*wakeup;
 	bool			wakeup_path:1;
 	bool			syscore:1;
+	bool			no_pm_callbacks:1;	/* Owned by the PM core */
 #else
 	unsigned int		should_wakeup:1;
 #endif
-- 
2.4.3

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