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 <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/storage/scsiglue.c

···
 
 	US_DEBUGP("%s called\n", __FUNCTION__);
 
-	/* lock the device pointers and do the reset */
-	mutex_lock(&(us->dev_mutex));
-	result = us->transport_reset(us);
-	mutex_unlock(&us->dev_mutex);
+	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

···
 {
 	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;
···
 {
 	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;
 }
 
···
 {
 	struct us_data *us = (struct us_data *)__us;
 	struct Scsi_Host *host = us_to_host(us);
+	int autopm_rc;
 
 	current->flags |= PF_NOFREEZE;
 
···
 			break;
 			
 		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));
···
 			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));
···
 
 		/* 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 */
···
 	}
 
 	scsi_host_put(us_to_host(us));
+	usb_autopm_put_interface(us->pusb_intf);
 	complete_and_exit(&threads_gone, 0);
 }
 
···
 	 * 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;
···
 	.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)