tty/serial: at91: BUG: disable interrupts when !UART_ENABLE_MS()

In set_termios(), interrupts where not disabled if UART_ENABLE_MS() was
false.

Tested on at91sam9g35.
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Cc: stable <stable@vger.kernel.org> # >= 3.16
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -526,6 +526,45 @@ static void atmel_enable_ms(struct uart_port *port)
 	UART_PUT_IER(port, ier);
 }
 
+/*
+ * Disable modem status interrupts
+ */
+static void atmel_disable_ms(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+	uint32_t idr = 0;
+
+	/*
+	 * Interrupt should not be disabled twice
+	 */
+	if (!atmel_port->ms_irq_enabled)
+		return;
+
+	atmel_port->ms_irq_enabled = false;
+
+	if (atmel_port->gpio_irq[UART_GPIO_CTS] >= 0)
+		disable_irq(atmel_port->gpio_irq[UART_GPIO_CTS]);
+	else
+		idr |= ATMEL_US_CTSIC;
+
+	if (atmel_port->gpio_irq[UART_GPIO_DSR] >= 0)
+		disable_irq(atmel_port->gpio_irq[UART_GPIO_DSR]);
+	else
+		idr |= ATMEL_US_DSRIC;
+
+	if (atmel_port->gpio_irq[UART_GPIO_RI] >= 0)
+		disable_irq(atmel_port->gpio_irq[UART_GPIO_RI]);
+	else
+		idr |= ATMEL_US_RIIC;
+
+	if (atmel_port->gpio_irq[UART_GPIO_DCD] >= 0)
+		disable_irq(atmel_port->gpio_irq[UART_GPIO_DCD]);
+	else
+		idr |= ATMEL_US_DCDIC;
+
+	UART_PUT_IDR(port, idr);
+}
+
 /*
  * Control the transmission of a break signal
  */
@@ -1993,7 +2032,9 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 
 	/* CTS flow-control and modem-status interrupts */
 	if (UART_ENABLE_MS(port, termios->c_cflag))
-		port->ops->enable_ms(port);
+		atmel_enable_ms(port);
+	else
+		atmel_disable_ms(port);
 
 	spin_unlock_irqrestore(&port->lock, flags);
 }