Commit 7d1cadca authored by Baruch Siach's avatar Baruch Siach Committed by Greg Kroah-Hartman
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serial: imx: support RS-485 Rx disable on Tx 



Some RS-232 to RS-485 transceivers require Rx to be disabled on Tx to
avoid echo of Tx data into the Rx buffer. Specifically, the XR3160E
RS-232/RS-485/RS-422 transceiver behaves this way.

This commit disables Rx on active Tx when SER_RS485_ENABLED is active and
SER_RS485_RX_DURING_TX is disabled.

Note that this is a change in behavior of the driver. Until now
SER_RS485_RX_DURING_TX was enabled unconditionally even when disabled in
the TIOCSRS485 ioctl serial_rs485 flags field.

Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarBaruch Siach <baruch@tkos.co.il>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3d23b4c3

drivers/tty/serial/imx.c

+12 −3
Original line number Diff line number Diff line
@@ -361,6 +361,7 @@ static void imx_stop_tx(struct uart_port *port) 
			imx_port_rts_inactive(sport, &temp);

		else

			imx_port_rts_active(sport, &temp);

		temp |= UCR2_RXEN;

		writel(temp, port->membase + UCR2);



		temp = readl(port->membase + UCR4);
@@ -568,6 +569,8 @@ static void imx_start_tx(struct uart_port *port) 
			imx_port_rts_inactive(sport, &temp);

		else

			imx_port_rts_active(sport, &temp);

		if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))

			temp &= ~UCR2_RXEN;

		writel(temp, port->membase + UCR2);



		/* enable transmitter and shifter empty irq */
@@ -1610,19 +1613,17 @@ static int imx_rs485_config(struct uart_port *port, 
			    struct serial_rs485 *rs485conf)

{

	struct imx_port *sport = (struct imx_port *)port;

	unsigned long temp;



	/* unimplemented */

	rs485conf->delay_rts_before_send = 0;

	rs485conf->delay_rts_after_send = 0;

	rs485conf->flags |= SER_RS485_RX_DURING_TX;



	/* RTS is required to control the transmitter */

	if (!sport->have_rtscts)

		rs485conf->flags &= ~SER_RS485_ENABLED;



	if (rs485conf->flags & SER_RS485_ENABLED) {

		unsigned long temp;



		/* disable transmitter */

		temp = readl(sport->port.membase + UCR2);

		if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND)
@@ -1632,6 +1633,14 @@ static int imx_rs485_config(struct uart_port *port, 
		writel(temp, sport->port.membase + UCR2);

	}



	/* Make sure Rx is enabled in case Tx is active with Rx disabled */

	if (!(rs485conf->flags & SER_RS485_ENABLED) ||

	    rs485conf->flags & SER_RS485_RX_DURING_TX) {

		temp = readl(sport->port.membase + UCR2);

		temp |= UCR2_RXEN;

		writel(temp, sport->port.membase + UCR2);

	}



	port->rs485 = *rs485conf;



	return 0;

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