[PATCH] tty: serial: imx: Fix broken RS485

[Rickard Andersson <rickaran@axis.com>]

From: Rickard x Andersson <rickaran@axis.com>

When about to transmit the function imx_uart_start_tx is called and in
some RS485 configurations this function will call imx_uart_stop_rx. The
problem is that imx_uart_stop_rx will enable loopback and when loopback
is enabled transmitted data will just be looped to RX.

This patch fixes the above problem by explicitly disabling loopback in
the case described above.

Signed-off-by: Rickard x Andersson <rickaran@axis.com>
---
 drivers/tty/serial/imx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 4aa72d5aeafb..899e331bdfc8 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -683,8 +683,15 @@ static void imx_uart_start_tx(struct uart_port *port)
 			imx_uart_writel(sport, ucr2, UCR2);
 
 			if (!(port->rs485.flags & SER_RS485_RX_DURING_TX) &&
-			    !port->rs485_rx_during_tx_gpio)
+			    !port->rs485_rx_during_tx_gpio) {
 				imx_uart_stop_rx(port);
+				/*
+				 * The function imx_uart_stop_rx right above
+				 * will enable loopback, but since we are just
+				 * about to transmit then disable loopback.
+				 */
+				imx_uart_disable_loopback_rs485(sport);
+			}
 
 			sport->tx_state = WAIT_AFTER_RTS;
 
-- 
2.30.2