serial: 8250_pci: add RS485 for F81504/508/512

Add RS485 control for Fintek F81504/508/512

F81504/508/512 can control their RTS with H/W mode.
PCI configuration space for each port is 0x40 + idx * 8 + 7.

When it set with 0x01, it's configured with RS232 mode.
RTS is controlled by MCR.

When it set with 0x11, it's configured with RS485 mode.
RTS is controlled by H/W, RTS low with idle & RX, high with TX.

When it set with 0x31, it's configured with RS485 mode.
RTS is controlled by H/W, RTS high with idle & RX, low with TX.

We will force 0x01 on pci_fintek_setup().

Signed-off-by: Peter Hung <hpeter+linux_kernel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_pci.c

@@ -1685,11 +1685,60 @@ pci_brcm_trumanage_setup(struct serial_private *priv,
 	return ret;
 }
 
+/* RTS will control by MCR if this bit is 0 */
+#define FINTEK_RTS_CONTROL_BY_HW	BIT(4)
+/* only worked with FINTEK_RTS_CONTROL_BY_HW on */
+#define FINTEK_RTS_INVERT		BIT(5)
+
+/* We should do proper H/W transceiver setting before change to RS485 mode */
+static int pci_fintek_rs485_config(struct uart_port *port,
+			       struct serial_rs485 *rs485)
+{
+	u8 setting;
+	u8 *index = (u8 *) port->private_data;
+	struct pci_dev *pci_dev = container_of(port->dev, struct pci_dev,
+						dev);
+
+	pci_read_config_byte(pci_dev, 0x40 + 8 * *index + 7, &setting);
+
+	if (rs485->flags & SER_RS485_ENABLED)
+		memset(rs485->padding, 0, sizeof(rs485->padding));
+	else
+		memset(rs485, 0, sizeof(*rs485));
+
+	/* F81504/508/512 not support RTS delay before or after send */
+	rs485->flags &= SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		/* Enable RTS H/W control mode */
+		setting |= FINTEK_RTS_CONTROL_BY_HW;
+
+		if (rs485->flags & SER_RS485_RTS_ON_SEND) {
+			/* RTS driving high on TX */
+			setting &= ~FINTEK_RTS_INVERT;
+		} else {
+			/* RTS driving low on TX */
+			setting |= FINTEK_RTS_INVERT;
+		}
+
+		rs485->delay_rts_after_send = 0;
+		rs485->delay_rts_before_send = 0;
+	} else {
+		/* Disable RTS H/W control mode */
+		setting &= ~(FINTEK_RTS_CONTROL_BY_HW | FINTEK_RTS_INVERT);
+	}
+
+	pci_write_config_byte(pci_dev, 0x40 + 8 * *index + 7, setting);
+	port->rs485 = *rs485;
+	return 0;
+}
+
 static int pci_fintek_setup(struct serial_private *priv,
 			    const struct pciserial_board *board,
 			    struct uart_8250_port *port, int idx)
 {
 	struct pci_dev *pdev = priv->dev;
+	u8 *data;
 	u8 config_base;
 	u16 iobase;
 
@@ -1702,6 +1751,15 @@ static int pci_fintek_setup(struct serial_private *priv,
 
 	port->port.iotype = UPIO_PORT;
 	port->port.iobase = iobase;
+	port->port.rs485_config = pci_fintek_rs485_config;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(u8), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* preserve index in PCI configuration space */
+	*data = idx;
+	port->port.private_data = data;
 
 	return 0;
 }
@@ -1752,6 +1810,9 @@ static int pci_fintek_init(struct pci_dev *dev)
 				(u8)((iobase & 0xff00) >> 8));
 
 		pci_write_config_byte(dev, config_base + 0x06, dev->irq);
+
+		/* force init to RS232 Mode */
+		pci_write_config_byte(dev, config_base + 0x07, 0x01);
 	}
 
 	return max_port;