[PATCH V2 5/7] USB: serial: f81232: Set F81534A serial port with RS232 mode

["Ji-Ze Hong (Peter Hong)" <hpeter@gmail.com>]

The Fintek F81532A/534A/535/536 is USB-to-2/4/8/12 serial ports device
and the serial ports are default disabled. Each port contains max 3 pins
GPIO and the 3 pins are default pull high with input mode.

When the serial port had activated (running probe()), we'll transform the
3 pins from GPIO function publicly to control Tranceiver privately use.
We'll default set to 0/0/1 for control transceiver to RS232 mode.

Otherwise, If the serial port is not active, the 3 pins is in GPIO mode
and controlled by global GPIO device with VID/PID: 2c42/16f8.

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
---
 drivers/usb/serial/f81232.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
index 36a17aedc2ae..01cb5a5ea1d2 100644
--- a/drivers/usb/serial/f81232.c
+++ b/drivers/usb/serial/f81232.c
@@ -96,6 +96,15 @@ MODULE_DEVICE_TABLE(usb, all_serial_id_table);
 #define F81534A_TRIGGER_MULTPILE_4X	BIT(3)
 #define F81534A_FIFO_128BYTE		(BIT(1) | BIT(0))
 
+/* Serial port self GPIO control, 2bytes [control&output data][input data] */
+#define F81534A_GPIO_REG		0x10e
+#define F81534A_GPIO_MODE2_DIR		BIT(6) /* 1: input, 0: output */
+#define F81534A_GPIO_MODE1_DIR		BIT(5)
+#define F81534A_GPIO_MODE0_DIR		BIT(4)
+#define F81534A_GPIO_MODE2_OUTPUT	BIT(2)
+#define F81534A_GPIO_MODE1_OUTPUT	BIT(1)
+#define F81534A_GPIO_MODE0_OUTPUT	BIT(0)
+
 struct f81232_private {
 	struct mutex lock;
 	u8 modem_control;
@@ -866,6 +875,14 @@ static int f81232_port_probe(struct usb_serial_port *port)
 
 static int f81534a_port_probe(struct usb_serial_port *port)
 {
+	int status;
+
+	/* tri-state with pull-high, default RS232 Mode */
+	status = f81232_set_register(port, F81534A_GPIO_REG,
+					F81534A_GPIO_MODE2_DIR);
+	if (status)
+		return status;
+
 	return f81232_port_probe(port);
 }
 
-- 
2.17.1