[PATCH v1 2/3] serial:8250:Add RS485 support for MCHP PCI1XXXX UART

[LakshmiPraveen Kopparthi]

UART module has built in support to control the RTS line. This patch 
adds the support to configure the HW control of RTS.

Signed-off-by: LakshmiPraveen Kopparthi <LakshmiPraveen.Kopparthi@xxxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_pci.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 12a3e0bd50aa..b06374fc6212 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1887,11 +1887,39 @@ pci_moxa_setup(struct serial_private *priv,
 #define PCI_SUBDEVICE_ID_MCHP_PCI1XXXX_1P3	0x000F
 
 #define UART_ACTV_REG 0x11
+#define ADC_CFG_REG 0x40
 #define UART_PCI_CTRL_REG 0x80
 #define UART_WAKE_REG 0x8C
 #define UART_WAKE_MASK_REG 0x90
 #define UART_RESET_REG 0x94
 
+#define ADC_EN BIT(0)
+#define ADC_PIN_SEL BIT(1)
+#define ADC_POLARITY BIT(2)
+
+static int mchp_pci1xxxx_rs485_config(struct uart_port *port,
+				      struct serial_rs485 *rs485)
+{
+	u8 data = 0;
+
+	memset(rs485->padding, 0, sizeof(rs485->padding));
+	rs485->flags &= SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
+
+	if (rs485->flags & SER_RS485_ENABLED) {
+		data = ADC_EN | ADC_PIN_SEL;
+		if (!(rs485->flags & SER_RS485_RTS_ON_SEND)) {
+			data |= ADC_POLARITY;
+			rs485->flags |=  SER_RS485_RTS_AFTER_SEND;
+		}
+	}
+
+	rs485->delay_rts_after_send = 0;
+	rs485->delay_rts_before_send = 0;
+	writeb(data, (port->membase + ADC_CFG_REG));
+	port->rs485 = *rs485;
+	return 0;
+}
+
 static char pci1xxxx_port_suspend(int line)
 {
 	struct uart_8250_port *up = serial8250_get_port(line);
@@ -2073,6 +2101,7 @@ static int mchp_pci1xxxx_setup(struct serial_private *priv,
 	offset = first_offset + idx * board->uart_offset;
 	port->port.flags |= UPF_FIXED_TYPE | UPF_SKIP_TEST;
 	port->port.type = PORT_MCHP16550A;
+	port->port.rs485_config = mchp_pci1xxxx_rs485_config;
 	ret = setup_port(priv, port, bar, offset, board->reg_shift);
 	if (ret < 0)
 		return ret;
-- 
2.25.1