usb-storage: implement autosuspend

This patch (as930) implements autosuspend for usb-storage.  It is
adapted from a patch by Oliver Neukum.  Autosuspend is allowed except
during LUN scanning, resets, and command execution.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/storage/scsiglue.c

@@ -285,10 +285,15 @@ static int device_reset(struct scsi_cmnd *srb)
 
 	US_DEBUGP("%s called\n", __FUNCTION__);
 
+	result = usb_autopm_get_interface(us->pusb_intf);
+	if (result == 0) {
+
 		/* lock the device pointers and do the reset */
 		mutex_lock(&(us->dev_mutex));
 		result = us->transport_reset(us);
 		mutex_unlock(&us->dev_mutex);
+		usb_autopm_put_interface(us->pusb_intf);
+	}
 
 	return result < 0 ? FAILED : SUCCESS;
 }

drivers/usb/storage/usb.c

@@ -191,16 +191,14 @@ static int storage_suspend(struct usb_interface *iface, pm_message_t message)
 {
 	struct us_data *us = usb_get_intfdata(iface);
 
+	US_DEBUGP("%s\n", __FUNCTION__);
+
 	/* Wait until no command is running */
 	mutex_lock(&us->dev_mutex);
 
-	US_DEBUGP("%s\n", __FUNCTION__);
 	if (us->suspend_resume_hook)
 		(us->suspend_resume_hook)(us, US_SUSPEND);
 
-	/* When runtime PM is working, we'll set a flag to indicate
-	 * whether we should autoresume when a SCSI request arrives. */
-
 	mutex_unlock(&us->dev_mutex);
 	return 0;
 }
@@ -209,13 +207,11 @@ static int storage_resume(struct usb_interface *iface)
 {
 	struct us_data *us = usb_get_intfdata(iface);
 
-	mutex_lock(&us->dev_mutex);
-
 	US_DEBUGP("%s\n", __FUNCTION__);
+
 	if (us->suspend_resume_hook)
 		(us->suspend_resume_hook)(us, US_RESUME);
 
-	mutex_unlock(&us->dev_mutex);
 	return 0;
 }
 
@@ -313,6 +309,7 @@ static int usb_stor_control_thread(void * __us)
 {
 	struct us_data *us = (struct us_data *)__us;
 	struct Scsi_Host *host = us_to_host(us);
+	int autopm_rc;
 
 	current->flags |= PF_NOFREEZE;
 
@@ -323,6 +320,9 @@ static int usb_stor_control_thread(void * __us)
 			
 		US_DEBUGP("*** thread awakened.\n");
 
+		/* Autoresume the device */
+		autopm_rc = usb_autopm_get_interface(us->pusb_intf);
+
 		/* lock the device pointers */
 		mutex_lock(&(us->dev_mutex));
 
@@ -381,6 +381,12 @@ static int usb_stor_control_thread(void * __us)
 			us->srb->result = SAM_STAT_GOOD;
 		}
 
+		/* Did the autoresume fail? */
+		else if (autopm_rc < 0) {
+			US_DEBUGP("Could not wake device\n");
+			us->srb->result = DID_ERROR << 16;
+		}
+
 		/* we've got a command, let's do it! */
 		else {
 			US_DEBUG(usb_stor_show_command(us->srb));
@@ -423,6 +429,10 @@ static int usb_stor_control_thread(void * __us)
 
 		/* unlock the device pointers */
 		mutex_unlock(&us->dev_mutex);
+
+		/* Start an autosuspend */
+		if (autopm_rc == 0)
+			usb_autopm_put_interface(us->pusb_intf);
 	} /* for (;;) */
 
 	/* Wait until we are told to stop */
@@ -939,6 +949,7 @@ static int usb_stor_scan_thread(void * __us)
 	}
 
 	scsi_host_put(us_to_host(us));
+	usb_autopm_put_interface(us->pusb_intf);
 	complete_and_exit(&threads_gone, 0);
 }
 
@@ -1028,6 +1039,7 @@ static int storage_probe(struct usb_interface *intf,
 	 * start it up. */
 	scsi_host_get(us_to_host(us));
 	atomic_inc(&total_threads);
+	usb_autopm_get_interface(intf); /* dropped in the scanning thread */
 	wake_up_process(th);
 
 	return 0;
@@ -1065,6 +1077,7 @@ static struct usb_driver usb_storage_driver = {
 	.pre_reset =	storage_pre_reset,
 	.post_reset =	storage_post_reset,
 	.id_table =	storage_usb_ids,
+	.supports_autosuspend = 1,
 };
 
 static int __init usb_stor_init(void)