linux-kernel - [PATCH v2 1/1] serial: fsl_lpuart: RS485 RTS polariy is inverse

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Date:   Fri,  5 Aug 2022 09:45:29 -0500
From:   Shenwei Wang <shenwei.wang@....com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-imx@....com, Shenwei Wang <shenwei.wang@....com>,
        Nicolas Diaz <nicolas.diaz@....com>
Subject: [PATCH v2 1/1] serial: fsl_lpuart: RS485 RTS polariy is inverse

The setting of RS485 RTS polarity is inverse in the current driver.

When the property of 'rs485-rts-active-low' is enabled in the dts node,
the RTS signal should be LOW during sending. Otherwise, if there is no
such a property, the RTS should be HIGH during sending.

Fixes: 03895cf41d18 ("tty: serial: fsl_lpuart: Add support for RS-485")

Signed-off-by: Nicolas Diaz <nicolas.diaz@....com>
Signed-off-by: Shenwei Wang <shenwei.wang@....com>

---
changes in v2:
- add the fix tag

 drivers/tty/serial/fsl_lpuart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index afa0f941c862..abc3a3674bc3 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1394,9 +1394,9 @@ static int lpuart_config_rs485(struct uart_port *port, struct ktermios *termios,
 		 * 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;
+		else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
+			modem &= ~UARTMODEM_TXRTSPOL;
 	}

 	writeb(modem, sport->port.membase + UARTMODEM);
--
2.25.1