diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index cdf4ebb93b10..8eab94cb06fa 100644
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -596,11 +596,13 @@ static int get_serial_info(struct tty_struct *tty,
 	struct gb_tty *gb_tty = tty->driver_data;
 
 	ss->line = gb_tty->minor;
+	mutex_lock(&gb_tty->port.mutex);
 	ss->close_delay = jiffies_to_msecs(gb_tty->port.close_delay) / 10;
 	ss->closing_wait =
 		gb_tty->port.closing_wait == ASYNC_CLOSING_WAIT_NONE ?
 		ASYNC_CLOSING_WAIT_NONE :
 		jiffies_to_msecs(gb_tty->port.closing_wait) / 10;
+	mutex_unlock(&gb_tty->port.mutex);
 
 	return 0;
 }