diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index ff8605b..c02e460 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -75,7 +75,7 @@
 	unsigned long last_dtr_rts;	/* saved modem control outputs */
 	struct async_icount	icount;
 	wait_queue_head_t delta_msr_wait; /* Used for TIOCMIWAIT */
-	char prev_status, diff_status;        /* Used for TIOCMIWAIT */
+	char prev_status;        /* Used for TIOCMIWAIT */
 	char transmit_empty;	/* If transmitter is empty or not */
 	struct usb_serial_port *port;
 	__u16 interface;	/* FT2232C, FT2232H or FT4232H port interface
@@ -1982,17 +1982,19 @@
 	   N.B. packet may be processed more than once, but differences
 	   are only processed once.  */
 	status = packet[0] & FTDI_STATUS_B0_MASK;
-	if (status & FTDI_RS0_CTS)
-		priv->icount.cts++;
-	if (status & FTDI_RS0_DSR)
-		priv->icount.dsr++;
-	if (status & FTDI_RS0_RI)
-		priv->icount.rng++;
-	if (status & FTDI_RS0_RLSD)
-		priv->icount.dcd++;
 	if (status != priv->prev_status) {
-		priv->diff_status |= status ^ priv->prev_status;
-		wake_up_interruptible(&priv->delta_msr_wait);
+		char diff_status = status ^ priv->prev_status;
+
+		if (diff_status & FTDI_RS0_CTS)
+			priv->icount.cts++;
+		if (diff_status & FTDI_RS0_DSR)
+			priv->icount.dsr++;
+		if (diff_status & FTDI_RS0_RI)
+			priv->icount.rng++;
+		if (diff_status & FTDI_RS0_RLSD)
+			priv->icount.dcd++;
+
+		wake_up_interruptible_all(&priv->delta_msr_wait);
 		priv->prev_status = status;
 	}