Enable Vybrid's build-in support for RS-485 auto RTS for controlling
line direction of RS-485 transceiver driver.
Enable RS485 feature by either using ioctrl 'TIOCSRS485' or enable it in
the device tree by setting 'linux,rs485-enabled-at-boot-time' property.
Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@xxxxxxxxxxx>
---
drivers/tty/serial/fsl_lpuart.c | 78 +++++++++++++++++++++++++++++++++++++----
1 file changed, 72 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 134090a..4d1fca4 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -917,6 +917,52 @@ static void lpuart_dma_rx_free(struct uart_port *port)
sport->dma_rx_cookie = -EINVAL;
}
+static int lpuart_config_rs485(struct uart_port *port,
+ struct serial_rs485 *rs485)
+{
+ struct lpuart_port *sport = container_of(port,
+ struct lpuart_port, port);
+
+ u8 modem = readb(sport->port.membase + UARTMODEM) &
+ ~(UARTMODEM_TXRTSPOL | UARTMODEM_TXRTSE);
+ writeb(modem, sport->port.membase + UARTMODEM);
+
+ if (rs485->flags & SER_RS485_ENABLED) {
+ /* Enable auto RS-485 RTS mode */
+ modem |= UARTMODEM_TXRTSE;
+
+ /*
+ * RTS needs to be logic HIGH either during transer _or_ after
+ * transfer, other variants are not supported by the hardware.
+ */
+
+ if (!(rs485->flags & (SER_RS485_RTS_ON_SEND |
+ SER_RS485_RTS_AFTER_SEND)))
+ rs485->flags |= SER_RS485_RTS_ON_SEND;
+
+ if (rs485->flags & SER_RS485_RTS_ON_SEND &&
+ rs485->flags & SER_RS485_RTS_AFTER_SEND)
+ rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
+
+ /*
+ * The hardware defaults to RTS logic HIGH while transfer.
+ * Switch polarity in case RTS shall be logic HIGH
+ * after transfer.
+ * Note: UART is assumed to be active high.
+ */
+ if (rs485->flags & SER_RS485_RTS_ON_SEND)
+ modem &= ~UARTMODEM_TXRTSPOL;
+ else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
+ modem |= UARTMODEM_TXRTSPOL;
+ }
+
+ /* Store the new configuration */
+ sport->port.rs485 = *rs485;
+
+ writeb(modem, sport->port.membase + UARTMODEM);
+ return 0;
+}
+
static unsigned int lpuart_get_mctrl(struct uart_port *port)
{
unsigned int temp = 0;
@@ -950,17 +996,22 @@ static unsigned int lpuart32_get_mctrl(struct uart_port *port)
static void lpuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
unsigned char temp;
+ struct lpuart_port *sport = container_of(port,
+ struct lpuart_port, port);
- temp = readb(port->membase + UARTMODEM) &
+ /* Make sure RXRTSE bit is not set when RS485 is enabled */
+ if (!(sport->port.rs485.flags & SER_RS485_ENABLED)) {
+ temp = readb(sport->port.membase + UARTMODEM) &
~(UARTMODEM_RXRTSE | UARTMODEM_TXCTSE);
- if (mctrl & TIOCM_RTS)
- temp |= UARTMODEM_RXRTSE;
+ if (mctrl & TIOCM_RTS)
+ temp |= UARTMODEM_RXRTSE;
- if (mctrl & TIOCM_CTS)
- temp |= UARTMODEM_TXCTSE;
+ if (mctrl & TIOCM_CTS)
+ temp |= UARTMODEM_TXCTSE;
- writeb(temp, port->membase + UARTMODEM);
+ writeb(temp, port->membase + UARTMODEM);
+ }
}
static void lpuart32_set_mctrl(struct uart_port *port, unsigned int mctrl)
@@ -1256,6 +1307,13 @@ lpuart_set_termios(struct uart_port *port, struct ktermios *termios,
cr1 |= UARTCR1_M;
}
+ /*
+ * When auto RS-485 RTS mode is enabled,
+ * hardware flow control need to be disabled.
+ */
+ if (sport->port.rs485.flags & SER_RS485_ENABLED)
+ termios->c_cflag &= ~CRTSCTS;
+
if (termios->c_cflag & CRTSCTS) {
modem |= (UARTMODEM_RXRTSE | UARTMODEM_TXCTSE);
} else {
@@ -1864,6 +1922,8 @@ static int lpuart_probe(struct platform_device *pdev)
sport->port.ops = &lpuart_pops;
sport->port.flags = UPF_BOOT_AUTOCONF;
+ sport->port.rs485_config = lpuart_config_rs485;
+
sport->clk = devm_clk_get(&pdev->dev, "ipg");
if (IS_ERR(sport->clk)) {
ret = PTR_ERR(sport->clk);
@@ -1904,6 +1964,12 @@ static int lpuart_probe(struct platform_device *pdev)
dev_info(sport->port.dev, "DMA rx channel request failed, "
"operating without rx DMA\n");
+ if (of_property_read_bool(np, "linux,rs485-enabled-at-boot-time")) {
+ sport->port.rs485.flags |= SER_RS485_ENABLED;
+ sport->port.rs485.flags |= SER_RS485_RTS_ON_SEND;
+ writeb(UARTMODEM_TXRTSE, sport->port.membase + UARTMODEM);
+ }
+
return 0;
}
--
2.8.3
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