FROMLIST: PM / sleep: Go direct_complete if driver has no callbacks

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.

BUG=chrome-os-partner:46491
TEST=suspend_stress_test on glados

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
(am from https://patchwork.kernel.org/patch/7328171/)
Signed-off-by: Derek Basehore <dbasehore@chromium.org>

Change-Id: Ic3d6cd732f6c64ef34f28e065454f690eed4e6f8
Reviewed-on: https://chromium-review.googlesource.com/305815
Commit-Ready: Derek Basehore <dbasehore@chromium.org>
Tested-by: Derek Basehore <dbasehore@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>

drivers/base/dd.c

@@ -219,6 +219,8 @@ static void driver_bound(struct device *dev)
 
 	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 
+	device_pm_check_callbacks(dev);
+
 	/*
 	 * Make sure the device is no longer in one of the deferred lists and
 	 * kick off retrying all pending devices
@@ -657,6 +659,7 @@ static void __device_release_driver(struct device *dev)
 		dev->driver = NULL;
 		dev_set_drvdata(dev, NULL);
 		klist_remove(&dev->p->knode_driver);
+		device_pm_check_callbacks(dev);
 		if (dev->bus)
 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 						     BUS_NOTIFY_UNBOUND_DRIVER,

drivers/base/power/common.c

@@ -14,6 +14,8 @@
 #include <linux/acpi.h>
 #include <linux/pm_domain.h>
 
+#include "power.h"
+
 /**
  * dev_pm_get_subsys_data - Create or refcount power.subsys_data for device.
  * @dev: Device to handle.
@@ -153,5 +155,6 @@ void dev_pm_domain_set(struct device *dev, struct dev_pm_domain *pd)
 	WARN(device_is_bound(dev),
 	     "PM domains can only be changed for unbound devices\n");
 	dev->pm_domain = pd;
+	device_pm_check_callbacks(dev);
 }
 EXPORT_SYMBOL_GPL(dev_pm_domain_set);

drivers/base/power/domain.c

@@ -18,6 +18,8 @@
 #include <linux/suspend.h>
 #include <linux/export.h>
 
+#include "power.h"
+
 #define GENPD_DEV_CALLBACK(genpd, type, callback, dev)		\
 ({								\
 	type (*__routine)(struct device *__d); 			\

drivers/base/power/main.c

@@ -126,6 +126,7 @@ void device_pm_add(struct device *dev)
 {
 	pr_debug("PM: Adding info for %s:%s\n",
 		 dev->bus ? dev->bus->name : "No Bus", dev_name(dev));
+	device_pm_check_callbacks(dev);
 	mutex_lock(&dpm_list_mtx);
 	if (dev->parent && dev->parent->power.is_prepared)
 		dev_warn(dev, "parent %s should not be sleeping\n",
@@ -148,6 +149,7 @@ void device_pm_remove(struct device *dev)
 	mutex_unlock(&dpm_list_mtx);
 	device_wakeup_disable(dev);
 	pm_runtime_remove(dev);
+	device_pm_check_callbacks(dev);
 }
 
 /**
@@ -1559,6 +1561,11 @@ 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;
@@ -1584,6 +1591,7 @@ static int device_prepare(struct device *dev, pm_message_t state)
 		trace_device_pm_callback_end(dev, ret);
 	}
 
+unlock:
 	device_unlock(dev);
 
 	if (ret < 0) {
@@ -1710,3 +1718,30 @@ 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_pm_check_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);
+}

drivers/base/power/power.h

@@ -51,6 +51,7 @@ extern void device_pm_remove(struct device *);
 extern void device_pm_move_before(struct device *, struct device *);
 extern void device_pm_move_after(struct device *, struct device *);
 extern void device_pm_move_last(struct device *);
+extern void device_pm_check_callbacks(struct device *dev);
 
 #else /* !CONFIG_PM_SLEEP */
 
@@ -69,6 +70,8 @@ static inline void device_pm_move_after(struct device *deva,
 					struct device *devb) {}
 static inline void device_pm_move_last(struct device *dev) {}
 
+static inline void device_pm_check_callbacks(struct device *dev) {}
+
 #endif /* !CONFIG_PM_SLEEP */
 
 static inline void device_pm_init(struct device *dev)

include/linux/pm.h

@@ -628,6 +628,7 @@ struct dev_pm_info {
 	enum wakeup_type	wakeup_source_type;
 	bool			wakeup_path:1;
 	bool			syscore:1;
+	bool			no_pm_callbacks:1;  /* Owned by the PM core */
 	bool			use_dark_resume:1;
 #else
 	unsigned int		should_wakeup:1;