tty: serial: samsung: Disable interrupts in a suspend-friendly way

Since the interrupt mask register is not preserved across system suspend
and it defaults to all interrupts enabled, it is not enough to disable
UART interrupt.

This patch adds free_irq to port shutdown and mask setting to port
startup to handle IRQ disabling in a suspend-friendly way. In addition,
a bug caused by multiple request_irq calls in port startup callback is
fixed.
Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/samsung.c

@@ -446,6 +446,8 @@ static void s3c24xx_serial_shutdown(struct uart_port *port)
 
 	/* Clear pending interrupts and mask all interrupts */
 	if (s3c24xx_serial_has_interrupt_mask(port)) {
+		free_irq(port->irq, ourport);
+
 		wr_regl(port, S3C64XX_UINTP, 0xf);
 		wr_regl(port, S3C64XX_UINTM, 0xf);
 	}
@@ -505,6 +507,8 @@ static int s3c64xx_serial_startup(struct uart_port *port)
 	dbg("s3c64xx_serial_startup: port=%p (%08lx,%p)\n",
 	    port->mapbase, port->membase);
 
+	wr_regl(port, S3C64XX_UINTM, 0xf);
+
 	ret = request_irq(port->irq, s3c64xx_serial_handle_irq, IRQF_SHARED,
 			  s3c24xx_serial_portname(port), ourport);
 	if (ret) {