tty: serial8250: allow platforms to override irq handler

Some ports (e.g. Synopsys DesignWare 8250) have special requirements for
handling the interrupts.  Allow these platforms to specify their own
interrupt handler that will override the default.
serial8250_handle_irq() is provided so that platforms can extend the IRQ
handler rather than completely replacing it.
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/tty/serial/8250.c

@@ -509,6 +509,8 @@ static void io_serial_out(struct uart_port *p, int offset, int value)
 	outb(value, p->iobase + offset);
 }
 
+static int serial8250_default_handle_irq(struct uart_port *port);
+
 static void set_io_from_upio(struct uart_port *p)
 {
 	struct uart_8250_port *up =
@@ -557,6 +559,7 @@ static void set_io_from_upio(struct uart_port *p)
 	}
 	/* Remember loaded iotype */
 	up->cur_iotype = p->iotype;
+	p->handle_irq = serial8250_default_handle_irq;
 }
 
 static void
@@ -1621,6 +1624,28 @@ static void serial8250_handle_port(struct uart_8250_port *up)
 	spin_unlock_irqrestore(&up->port.lock, flags);
 }
 
+int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
+{
+	struct uart_8250_port *up =
+		container_of(port, struct uart_8250_port, port);
+
+	if (!(iir & UART_IIR_NO_INT)) {
+		serial8250_handle_port(up);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int serial8250_default_handle_irq(struct uart_port *port)
+{
+	struct uart_8250_port *up =
+		container_of(port, struct uart_8250_port, port);
+	unsigned int iir = serial_in(up, UART_IIR);
+
+	return serial8250_handle_irq(port, iir);
+}
+
 /*
  * This is the serial driver's interrupt routine.
  *
@@ -1648,13 +1673,12 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
 	l = i->head;
 	do {
 		struct uart_8250_port *up;
-		unsigned int iir;
+		struct uart_port *port;
 
 		up = list_entry(l, struct uart_8250_port, list);
+		port = &up->port;
 
-		iir = serial_in(up, UART_IIR);
-		if (!(iir & UART_IIR_NO_INT)) {
-			serial8250_handle_port(up);
+		if (port->handle_irq(port)) {
 
 			handled = 1;
 
@@ -3048,6 +3072,10 @@ int __init early_serial_setup(struct uart_port *port)
 		p->serial_in = port->serial_in;
 	if (port->serial_out)
 		p->serial_out = port->serial_out;
+	if (port->handle_irq)
+		p->handle_irq = port->handle_irq;
+	else
+		p->handle_irq = serial8250_default_handle_irq;
 
 	return 0;
 }
@@ -3116,6 +3144,7 @@ static int __devinit serial8250_probe(struct platform_device *dev)
 		port.type		= p->type;
 		port.serial_in		= p->serial_in;
 		port.serial_out		= p->serial_out;
+		port.handle_irq		= p->handle_irq;
 		port.set_termios	= p->set_termios;
 		port.pm			= p->pm;
 		port.dev		= &dev->dev;
@@ -3281,6 +3310,8 @@ int serial8250_register_port(struct uart_port *port)
 			uart->port.serial_in = port->serial_in;
 		if (port->serial_out)
 			uart->port.serial_out = port->serial_out;
+		if (port->handle_irq)
+			uart->port.handle_irq = port->handle_irq;
 		/*  Possibly override set_termios call */
 		if (port->set_termios)
 			uart->port.set_termios = port->set_termios;

include/linux/serial_8250.h

@@ -35,6 +35,7 @@ struct plat_serial8250_port {
 	void		(*set_termios)(struct uart_port *,
 			               struct ktermios *new,
 			               struct ktermios *old);
+	int		(*handle_irq)(struct uart_port *);
 	void		(*pm)(struct uart_port *, unsigned int state,
 			      unsigned old);
 };
@@ -80,6 +81,7 @@ extern void serial8250_do_set_termios(struct uart_port *port,
 		struct ktermios *termios, struct ktermios *old);
 extern void serial8250_do_pm(struct uart_port *port, unsigned int state,
 			     unsigned int oldstate);
+int serial8250_handle_irq(struct uart_port *port, unsigned int iir);
 
 extern void serial8250_set_isa_configurator(void (*v)
 					(int port, struct uart_port *up,