diff --git a/drivers/serial/bfin_5xx.c b/drivers/serial/bfin_5xx.c
index 511cbf687877..a9eff2b18eab 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -957,15 +957,12 @@ bfin_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
  * Enable the IrDA function if tty->ldisc.num is N_IRDA.
  * In other cases, disable IrDA function.
  */
-static void bfin_serial_set_ldisc(struct uart_port *port)
+static void bfin_serial_set_ldisc(struct uart_port *port, int ld)
 {
 	int line = port->line;
 	unsigned short val;
 
-	if (line >= port->state->port.tty->driver->num)
-		return;
-
-	switch (port->state->port.tty->termios->c_line) {
+	switch (ld) {
 	case N_IRDA:
 		val = UART_GET_GCTL(&bfin_serial_ports[line]);
 		val |= (IREN | RPOLC);
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 12ee7e0f99ce..570dca2935e2 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1194,7 +1194,7 @@ static void uart_set_ldisc(struct tty_struct *tty)
 	struct uart_port *uport = state->uart_port;
 
 	if (uport->ops->set_ldisc)
-		uport->ops->set_ldisc(uport);
+		uport->ops->set_ldisc(uport, tty->termios->c_line);
 }
 
 static void uart_set_termios(struct tty_struct *tty,
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index f10db6e5f3b5..32928161fab6 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -220,7 +220,7 @@ struct uart_ops {
 	void		(*flush_buffer)(struct uart_port *);
 	void		(*set_termios)(struct uart_port *, struct ktermios *new,
 				       struct ktermios *old);
-	void		(*set_ldisc)(struct uart_port *);
+	void		(*set_ldisc)(struct uart_port *, int new);
 	void		(*pm)(struct uart_port *, unsigned int state,
 			      unsigned int oldstate);
 	int		(*set_wake)(struct uart_port *, unsigned int state);