USB: add "last_busy" field for use in autosuspend

This patch (as877) adds a "last_busy" field to struct usb_device, for
use by the autosuspend framework.  Now if an autosuspend call comes at
a time when the device isn't busy but hasn't yet been idle for long
enough, the timer can be set to exactly the desired value.  And we
will be ready to handle things like HID drivers, which can't maintain
a useful usage count and must rely on the time-of-last-use to decide
when to autosuspend.

The patch also makes some related minor improvements:

	Move the calls to the autosuspend condition-checking routine
	into usb_suspend_both(), which is the only place where it
	really matters.

	If the autosuspend timer is already running, don't stop
	and restart it.

	Replace immediate returns with gotos so that the optional
	debugging ouput won't be bypassed.

	If autoresume is disabled but the device is already awake,
	don't return an error for an autoresume call.

	Don't try to autoresume a device if it isn't suspended.
	(Yes, this undercuts the previous change -- so sue me.)

	Don't duplicate existing code in the autosuspend work routine.

	Fix the kerneldoc in usb_autopm_put_interface(): If an
	autoresume call fails, the usage counter is left unchanged.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/driver.c

@@ -932,6 +932,7 @@ static int autosuspend_check(struct usb_device *udev)
 {
 	int			i;
 	struct usb_interface	*intf;
+	long			suspend_time;
 
 	/* For autosuspend, fail fast if anything is in use or autosuspend
 	 * is disabled.  Also fail if any interfaces require remote wakeup
@@ -943,6 +944,7 @@ static int autosuspend_check(struct usb_device *udev)
 	if (udev->autosuspend_delay < 0 || udev->autosuspend_disabled)
 		return -EPERM;
 
+	suspend_time = udev->last_busy + udev->autosuspend_delay;
 	if (udev->actconfig) {
 		for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
 			intf = udev->actconfig->interface[i];
@@ -958,6 +960,17 @@ static int autosuspend_check(struct usb_device *udev)
 			}
 		}
 	}
+
+	/* If everything is okay but the device hasn't been idle for long
+	 * enough, queue a delayed autosuspend request.
+	 */
+	suspend_time -= jiffies;
+	if (suspend_time > 0) {
+		if (!timer_pending(&udev->autosuspend.timer))
+			queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
+					suspend_time);
+		return -EAGAIN;
+	}
 	return 0;
 }
 
@@ -1010,19 +1023,18 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 	struct usb_interface	*intf;
 	struct usb_device	*parent = udev->parent;
 
-	cancel_delayed_work(&udev->autosuspend);
-	if (udev->state == USB_STATE_NOTATTACHED)
-		return 0;
-	if (udev->state == USB_STATE_SUSPENDED)
-		return 0;
+	if (udev->state == USB_STATE_NOTATTACHED ||
+			udev->state == USB_STATE_SUSPENDED)
+		goto done;
 
 	udev->do_remote_wakeup = device_may_wakeup(&udev->dev);
 
 	if (udev->auto_pm) {
 		status = autosuspend_check(udev);
 		if (status < 0)
-			return status;
+			goto done;
 	}
+	cancel_delayed_work(&udev->autosuspend);
 
 	/* Suspend all the interfaces and then udev itself */
 	if (udev->actconfig) {
@@ -1047,6 +1059,7 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 	} else if (parent)
 		usb_autosuspend_device(parent);
 
+ done:
 	// dev_dbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
 	return status;
 }
@@ -1086,14 +1099,18 @@ static int usb_resume_both(struct usb_device *udev)
 	struct usb_interface	*intf;
 	struct usb_device	*parent = udev->parent;
 
-	if (udev->auto_pm && udev->autoresume_disabled)
-		return -EPERM;
 	cancel_delayed_work(&udev->autosuspend);
-	if (udev->state == USB_STATE_NOTATTACHED)
-		return -ENODEV;
+	if (udev->state == USB_STATE_NOTATTACHED) {
+		status = -ENODEV;
+		goto done;
+	}
 
 	/* Propagate the resume up the tree, if necessary */
 	if (udev->state == USB_STATE_SUSPENDED) {
+		if (udev->auto_pm && udev->autoresume_disabled) {
+			status = -EPERM;
+			goto done;
+		}
 		if (parent) {
 			status = usb_autoresume_device(parent);
 			if (status == 0) {
@@ -1139,24 +1156,13 @@ static int usb_resume_both(struct usb_device *udev)
 		}
 	}
 
+ done:
 	// dev_dbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
 	return status;
 }
 
 #ifdef CONFIG_USB_SUSPEND
 
-/* usb_autosuspend_work - callback routine to autosuspend a USB device */
-void usb_autosuspend_work(struct work_struct *work)
-{
-	struct usb_device *udev =
-		container_of(work, struct usb_device, autosuspend.work);
-
-	usb_pm_lock(udev);
-	udev->auto_pm = 1;
-	usb_suspend_both(udev, PMSG_SUSPEND);
-	usb_pm_unlock(udev);
-}
-
 /* Internal routine to adjust a device's usage counter and change
  * its autosuspend state.
  */
@@ -1165,20 +1171,34 @@ static int usb_autopm_do_device(struct usb_device *udev, int inc_usage_cnt)
 	int	status = 0;
 
 	usb_pm_lock(udev);
+	udev->auto_pm = 1;
 	udev->pm_usage_cnt += inc_usage_cnt;
 	WARN_ON(udev->pm_usage_cnt < 0);
 	if (inc_usage_cnt >= 0 && udev->pm_usage_cnt > 0) {
-		udev->auto_pm = 1;
-		status = usb_resume_both(udev);
+		if (udev->state == USB_STATE_SUSPENDED)
+			status = usb_resume_both(udev);
 		if (status != 0)
 			udev->pm_usage_cnt -= inc_usage_cnt;
-	} else if (inc_usage_cnt <= 0 && autosuspend_check(udev) == 0)
-		queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
-				udev->autosuspend_delay);
+		else if (inc_usage_cnt)
+			udev->last_busy = jiffies;
+	} else if (inc_usage_cnt <= 0 && udev->pm_usage_cnt <= 0) {
+		if (inc_usage_cnt)
+			udev->last_busy = jiffies;
+		status = usb_suspend_both(udev, PMSG_SUSPEND);
+	}
 	usb_pm_unlock(udev);
 	return status;
 }
 
+/* usb_autosuspend_work - callback routine to autosuspend a USB device */
+void usb_autosuspend_work(struct work_struct *work)
+{
+	struct usb_device *udev =
+		container_of(work, struct usb_device, autosuspend.work);
+
+	usb_autopm_do_device(udev, 0);
+}
+
 /**
  * usb_autosuspend_device - delayed autosuspend of a USB device and its interfaces
  * @udev: the usb_device to autosuspend
@@ -1270,15 +1290,20 @@ static int usb_autopm_do_interface(struct usb_interface *intf,
 	if (intf->condition == USB_INTERFACE_UNBOUND)
 		status = -ENODEV;
 	else {
+		udev->auto_pm = 1;
 		intf->pm_usage_cnt += inc_usage_cnt;
 		if (inc_usage_cnt >= 0 && intf->pm_usage_cnt > 0) {
-			udev->auto_pm = 1;
-			status = usb_resume_both(udev);
+			if (udev->state == USB_STATE_SUSPENDED)
+				status = usb_resume_both(udev);
 			if (status != 0)
 				intf->pm_usage_cnt -= inc_usage_cnt;
-		} else if (inc_usage_cnt <= 0 && autosuspend_check(udev) == 0)
-			queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
-					udev->autosuspend_delay);
+			else if (inc_usage_cnt)
+				udev->last_busy = jiffies;
+		} else if (inc_usage_cnt <= 0 && intf->pm_usage_cnt <= 0) {
+			if (inc_usage_cnt)
+				udev->last_busy = jiffies;
+			status = usb_suspend_both(udev, PMSG_SUSPEND);
+		}
 	}
 	usb_pm_unlock(udev);
 	return status;
@@ -1337,11 +1362,14 @@ EXPORT_SYMBOL_GPL(usb_autopm_put_interface);
  * or @intf is unbound.  A typical example would be a character-device
  * driver when its device file is opened.
  *
- * The routine increments @intf's usage counter.  So long as the counter
- * is greater than 0, autosuspend will not be allowed for @intf or its
- * usb_device.  When the driver is finished using @intf it should call
- * usb_autopm_put_interface() to decrement the usage counter and queue
- * a delayed autosuspend request (if the counter is <= 0).
+ *
+ * The routine increments @intf's usage counter.  (However if the
+ * autoresume fails then the counter is re-decremented.)  So long as the
+ * counter is greater than 0, autosuspend will not be allowed for @intf
+ * or its usb_device.  When the driver is finished using @intf it should
+ * call usb_autopm_put_interface() to decrement the usage counter and
+ * queue a delayed autosuspend request (if the counter is <= 0).
+ *
  *
  * Note that @intf->pm_usage_cnt is owned by the interface driver.  The
  * core will not change its value other than the increment and decrement

drivers/usb/core/hcd.c

@@ -1306,6 +1306,7 @@ static void hcd_resume_work(struct work_struct *work)
 	struct usb_device *udev = hcd->self.root_hub;
 
 	usb_lock_device(udev);
+	usb_mark_last_busy(udev);
 	usb_external_resume_device(udev);
 	usb_unlock_device(udev);
 }

drivers/usb/core/hub.c

@@ -1859,6 +1859,7 @@ static int remote_wakeup(struct usb_device *udev)
 	usb_lock_device(udev);
 	if (udev->state == USB_STATE_SUSPENDED) {
 		dev_dbg(&udev->dev, "usb %sresume\n", "wakeup-");
+		usb_mark_last_busy(udev);
 		status = usb_external_resume_device(udev);
 	}
 	usb_unlock_device(udev);

include/linux/usb.h

@@ -398,6 +398,7 @@ struct usb_device {
 	struct delayed_work autosuspend; /* for delayed autosuspends */
 	struct mutex pm_mutex;		/* protects PM operations */
 
+	unsigned long last_busy;	/* time of last use */
 	int autosuspend_delay;		/* in jiffies */
 
 	unsigned auto_pm:1;		/* autosuspend/resume in progress */
@@ -443,6 +444,11 @@ static inline void usb_autopm_disable(struct usb_interface *intf)
 	usb_autopm_set_interface(intf);
 }
 
+static inline void usb_mark_last_busy(struct usb_device *udev)
+{
+	udev->last_busy = jiffies;
+}
+
 #else
 
 static inline int usb_autopm_set_interface(struct usb_interface *intf)
@@ -457,6 +463,8 @@ static inline void usb_autopm_enable(struct usb_interface *intf)
 { }
 static inline void usb_autopm_disable(struct usb_interface *intf)
 { }
+static inline void usb_mark_last_busy(struct usb_device *udev)
+{ }
 #endif
 
 /*-------------------------------------------------------------------------*/