From d984fe91a85e49841449b120cda5a50fed1fb126 Mon Sep 17 00:00:00 2001
From: Johan Hovold <jhovold@gmail.com>
Date: Thu, 2 Jan 2014 22:49:31 +0100
Subject: [PATCH] USB: ch341: only wake up MSR queue on changes

Only wake up MSR wait queue on actual modem-status changes.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/serial/ch341.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 025b7857a36c..acc88650ac0a 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -460,6 +460,9 @@ static void ch341_update_line_status(struct usb_serial_port *port,
 	if (data[1] & CH341_MULT_STAT)
 		dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
 
+	if (!delta)
+		return;
+
 	if (delta & CH341_BIT_DCD) {
 		tty = tty_port_tty_get(&port->port);
 		if (tty) {