USB: add asynchronous autosuspend/autoresume support

This patch (as1160b) adds support routines for asynchronous autosuspend
and autoresume, with accompanying documentation updates.  There
already are several potential users of this interface, and others are
likely to arise as autosuspend support becomes more widespread.

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

4 files changed, 91 insertions, 2 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 8c081308b0e..23b3c7e79d4 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1341,6 +1341,19 @@ void usb_autosuspend_work(struct work_struct *work)
 	usb_autopm_do_device(udev, 0);
 }
 
+/* usb_autoresume_work - callback routine to autoresume a USB device */
+void usb_autoresume_work(struct work_struct *work)
+{
+	struct usb_device *udev =
+		container_of(work, struct usb_device, autoresume);
+
+	/* Wake it up, let the drivers do their thing, and then put it
+	 * back to sleep.
+	 */
+	if (usb_autopm_do_device(udev, 1) == 0)
+		usb_autopm_do_device(udev, -1);
+}
+
 /**
  * usb_autosuspend_device - delayed autosuspend of a USB device and its interfaces
  * @udev: the usb_device to autosuspend
@@ -1492,6 +1505,45 @@ void usb_autopm_put_interface(struct usb_interface *intf)
 EXPORT_SYMBOL_GPL(usb_autopm_put_interface);
 
 /**
+ * usb_autopm_put_interface_async - decrement a USB interface's PM-usage counter
+ * @intf: the usb_interface whose counter should be decremented
+ *
+ * This routine does essentially the same thing as
+ * usb_autopm_put_interface(): it decrements @intf's usage counter and
+ * queues a delayed autosuspend request if the counter is <= 0.  The
+ * difference is that it does not acquire the device's pm_mutex;
+ * callers must handle all synchronization issues themselves.
+ *
+ * Typically a driver would call this routine during an URB's completion
+ * handler, if no more URBs were pending.
+ *
+ * This routine can run in atomic context.
+ */
+void usb_autopm_put_interface_async(struct usb_interface *intf)
+{
+	struct usb_device	*udev = interface_to_usbdev(intf);
+	int			status = 0;
+
+	if (intf->condition == USB_INTERFACE_UNBOUND) {
+		status = -ENODEV;
+	} else {
+		udev->last_busy = jiffies;
+		--intf->pm_usage_cnt;
+		if (udev->autosuspend_disabled || udev->autosuspend_delay < 0)
+			status = -EPERM;
+		else if (intf->pm_usage_cnt <= 0 &&
+				!timer_pending(&udev->autosuspend.timer)) {
+			queue_delayed_work(ksuspend_usb_wq, &udev->autosuspend,
+					round_jiffies_relative(
+						udev->autosuspend_delay));
+		}
+	}
+	dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
+			__func__, status, intf->pm_usage_cnt);
+}
+EXPORT_SYMBOL_GPL(usb_autopm_put_interface_async);
+
+/**
  * usb_autopm_get_interface - increment a USB interface's PM-usage counter
  * @intf: the usb_interface whose counter should be incremented
  *
@@ -1537,6 +1589,37 @@ int usb_autopm_get_interface(struct usb_interface *intf)
 EXPORT_SYMBOL_GPL(usb_autopm_get_interface);
 
 /**
+ * usb_autopm_get_interface_async - increment a USB interface's PM-usage counter
+ * @intf: the usb_interface whose counter should be incremented
+ *
+ * This routine does much the same thing as
+ * usb_autopm_get_interface(): it increments @intf's usage counter and
+ * queues an autoresume request if the result is > 0.  The differences
+ * are that it does not acquire the device's pm_mutex (callers must
+ * handle all synchronization issues themselves), and it does not
+ * autoresume the device directly (it only queues a request).  After a
+ * successful call, the device will generally not yet be resumed.
+ *
+ * This routine can run in atomic context.
+ */
+int usb_autopm_get_interface_async(struct usb_interface *intf)
+{
+	struct usb_device	*udev = interface_to_usbdev(intf);
+	int			status = 0;
+
+	if (intf->condition == USB_INTERFACE_UNBOUND)
+		status = -ENODEV;
+	else if (udev->autoresume_disabled)
+		status = -EPERM;
+	else if (++intf->pm_usage_cnt > 0 && udev->state == USB_STATE_SUSPENDED)
+		queue_work(ksuspend_usb_wq, &udev->autoresume);
+	dev_vdbg(&intf->dev, "%s: status %d cnt %d\n",
+			__func__, status, intf->pm_usage_cnt);
+	return status;
+}
+EXPORT_SYMBOL_GPL(usb_autopm_get_interface_async);
+
+/**
  * usb_autopm_set_interface - set a USB interface's autosuspend state
  * @intf: the usb_interface whose state should be set
  *
@@ -1563,6 +1646,9 @@ EXPORT_SYMBOL_GPL(usb_autopm_set_interface);
 void usb_autosuspend_work(struct work_struct *work)
 {}
 
+void usb_autoresume_work(struct work_struct *work)
+{}
+
 #endif /* CONFIG_USB_SUSPEND */
 
 /**
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b19cbfcd51d..95fb3104ba4 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1374,8 +1374,9 @@ static void usb_stop_pm(struct usb_device *udev)
 		usb_autosuspend_device(udev->parent);
 	usb_pm_unlock(udev);
 
-	/* Stop any autosuspend requests already submitted */
-	cancel_rearming_delayed_work(&udev->autosuspend);
+	/* Stop any autosuspend or autoresume requests already submitted */
+	cancel_delayed_work_sync(&udev->autosuspend);
+	cancel_work_sync(&udev->autoresume);
 }
 
 #else
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 400fa4cc9a3..44f2fc750b6 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -402,6 +402,7 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
 #ifdef	CONFIG_PM
 	mutex_init(&dev->pm_mutex);
 	INIT_DELAYED_WORK(&dev->autosuspend, usb_autosuspend_work);
+	INIT_WORK(&dev->autoresume, usb_autoresume_work);
 	dev->autosuspend_delay = usb_autosuspend_delay * HZ;
 	dev->connect_time = jiffies;
 	dev->active_duration = -jiffies;
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index 9a1a45ac3ad..b60ebb4de1a 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -45,6 +45,7 @@ extern int usb_suspend(struct device *dev, pm_message_t msg);
 extern int usb_resume(struct device *dev);
 
 extern void usb_autosuspend_work(struct work_struct *work);
+extern void usb_autoresume_work(struct work_struct *work);
 extern int usb_port_suspend(struct usb_device *dev);
 extern int usb_port_resume(struct usb_device *dev);
 extern int usb_external_suspend_device(struct usb_device *udev,