USB: serial: xr: move pin configuration to probe

There's no need to configure the pins on every open and judging from the
vendor driver and datasheet it can be done before enabling the UART.

Move pin configuration from open() to port probe and make sure to
deassert DTR and RTS after configuring all pins as GPIO.
Signed-off-by: NJohan Hovold <johan@kernel.org>

drivers/usb/serial/xr_serial.c

@@ -532,7 +532,6 @@ static void xr_set_termios(struct tty_struct *tty,
 
 static int xr_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
-	u8 gpio_dir;
 	int ret;
 
 	ret = xr_uart_enable(port);
@@ -541,13 +540,6 @@ static int xr_open(struct tty_struct *tty, struct usb_serial_port *port)
 		return ret;
 	}
 
-	/*
-	 * Configure DTR and RTS as outputs and RI, CD, DSR and CTS as
-	 * inputs.
-	 */
-	gpio_dir = XR21V141X_GPIO_DTR | XR21V141X_GPIO_RTS;
-	xr_set_reg_uart(port, XR21V141X_REG_GPIO_DIR, gpio_dir);
-
 	/* Setup termios */
 	if (tty)
 		xr_set_termios(tty, port, NULL);
@@ -596,10 +588,38 @@ static int xr_probe(struct usb_serial *serial, const struct usb_device_id *id)
 	return 0;
 }
 
+static int xr_gpio_init(struct usb_serial_port *port)
+{
+	u8 mask, mode;
+	int ret;
+
+	/* Configure all pins as GPIO. */
+	mode = 0;
+	ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_MODE, mode);
+	if (ret)
+		return ret;
+
+	/*
+	 * Configure DTR and RTS as outputs and make sure they are deasserted
+	 * (active low), and configure RI, CD, DSR and CTS as inputs.
+	 */
+	mask = XR21V141X_GPIO_DTR | XR21V141X_GPIO_RTS;
+	ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_DIR, mask);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_SET, mask);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
 static int xr_port_probe(struct usb_serial_port *port)
 {
 	struct usb_interface_descriptor *desc;
 	struct xr_data *data;
+	int ret;
 
 	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (!data)
@@ -610,7 +630,16 @@ static int xr_port_probe(struct usb_serial_port *port)
 
 	usb_set_serial_port_data(port, data);
 
+	ret = xr_gpio_init(port);
+	if (ret)
+		goto err_free;
+
 	return 0;
+
+err_free:
+	kfree(data);
+
+	return ret;
 }
 
 static void xr_port_remove(struct usb_serial_port *port)