diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 7c4ebe6ee18b133247a591177df0c556c1f0bd09..c3db16b7afa12f6b43e94fe5437bde3ca7aeea4a 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2407,6 +2407,21 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
 		tty_termios_encode_baud_rate(termios, baud, baud);
 }
 
+static void
+serial8250_set_ldisc(struct uart_port *port)
+{
+	int line = port->line;
+
+	if (line >= port->state->port.tty->driver->num)
+		return;
+
+	if (port->state->port.tty->ldisc->ops->num == N_PPS) {
+		port->flags |= UPF_HARDPPS_CD;
+		serial8250_enable_ms(port);
+	} else
+		port->flags &= ~UPF_HARDPPS_CD;
+}
+
 static void
 serial8250_pm(struct uart_port *port, unsigned int state,
 	      unsigned int oldstate)
@@ -2628,6 +2643,7 @@ static struct uart_ops serial8250_pops = {
 	.startup	= serial8250_startup,
 	.shutdown	= serial8250_shutdown,
 	.set_termios	= serial8250_set_termios,
+	.set_ldisc	= serial8250_set_ldisc,
 	.pm		= serial8250_pm,
 	.type		= serial8250_type,
 	.release_port	= serial8250_release_port,