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Commit 03895cf4 authored by Bhuvanchandra DV's avatar Bhuvanchandra DV Committed by Greg Kroah-Hartman
Browse files

tty: serial: fsl_lpuart: Add support for RS-485 



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: default avatarBhuvanchandra DV <bhuvanchandra.dv@toradex.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c05efd69

drivers/tty/serial/fsl_lpuart.c

+72 −6
Original line number Diff line number Diff line
@@ -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;
@@ -950,8 +996,12 @@ 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)
@@ -962,6 +1012,7 @@ static void lpuart_set_mctrl(struct uart_port *port, unsigned int mctrl) 


		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 {
@@ -1870,6 +1928,8 @@ 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);
@@ -1910,6 +1970,12 @@ 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;

}