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serial: imx: support RS-485 Rx disable on Tx

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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 <[email protected]>
Signed-off-by: Baruch Siach <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Baruch Siach authored and Greg Kroah-Hartman committed 2016-04-30 09:26:55 -07:00
1 parent 3d23b4c364
commit 7d1cadca95
1 file changed
+12 -3
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drivers/tty/serial/imx.c
+12 -3
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@@ -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;