serial amba-pl010: enable PPS support

Function pl010_enable_ms() is automagically called when PPS ldisc
is selected.

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg KH <greg@kroah.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/serial/amba-pl010.c

@@ -471,6 +471,20 @@ pl010_set_termios(struct uart_port *port, struct ktermios *termios,
 	spin_unlock_irqrestore(&uap->port.lock, flags);
 }
 
+static void pl010_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;
+		pl010_enable_ms(port);
+	} else
+		port->flags &= ~UPF_HARDPPS_CD;
+}
+
 static const char *pl010_type(struct uart_port *port)
 {
 	return port->type == PORT_AMBA ? "AMBA" : NULL;
@@ -531,6 +545,7 @@ static struct uart_ops amba_pl010_pops = {
 	.startup	= pl010_startup,
 	.shutdown	= pl010_shutdown,
 	.set_termios	= pl010_set_termios,
+	.set_ldisc	= pl010_set_ldisc,
 	.type		= pl010_type,
 	.release_port	= pl010_release_port,
 	.request_port	= pl010_request_port,