diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index 8efa19d0e9fb..ba7352e4187e 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -111,7 +111,6 @@ struct cypress_private {
 	int baud_rate;			   /* stores current baud rate in
 					      integer form */
 	int isthrottled;		   /* if throttled, discard reads */
-	wait_queue_head_t delta_msr_wait;  /* used for TIOCMIWAIT */
 	char prev_status, diff_status;	   /* used for TIOCMIWAIT */
 	/* we pass a pointer to this as the argument sent to
 	   cypress_set_termios old_termios */
@@ -449,7 +448,6 @@ static int cypress_generic_port_probe(struct usb_serial_port *port)
 		kfree(priv);
 		return -ENOMEM;
 	}
-	init_waitqueue_head(&priv->delta_msr_wait);
 
 	usb_reset_configuration(serial->dev);
 
@@ -868,12 +866,16 @@ static int cypress_ioctl(struct tty_struct *tty,
 	switch (cmd) {
 	/* This code comes from drivers/char/serial.c and ftdi_sio.c */
 	case TIOCMIWAIT:
-		while (priv != NULL) {
-			interruptible_sleep_on(&priv->delta_msr_wait);
+		for (;;) {
+			interruptible_sleep_on(&port->delta_msr_wait);
 			/* see if a signal did it */
 			if (signal_pending(current))
 				return -ERESTARTSYS;
-			else {
+
+			if (port->serial->disconnected)
+				return -EIO;
+
+			{
 				char diff = priv->diff_status;
 				if (diff == 0)
 					return -EIO; /* no change => error */
@@ -1187,7 +1189,7 @@ static void cypress_read_int_callback(struct urb *urb)
 	if (priv->current_status != priv->prev_status) {
 		priv->diff_status |= priv->current_status ^
 			priv->prev_status;
-		wake_up_interruptible(&priv->delta_msr_wait);
+		wake_up_interruptible(&port->delta_msr_wait);
 		priv->prev_status = priv->current_status;
 	}
 	spin_unlock_irqrestore(&priv->lock, flags);