linux-kernel - [PATCH 4.9 04/42] serial: fsl_lpuart: RS485 RTS polariy is inverse

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Message-Id: <20220913140342.463369308@linuxfoundation.org>
Date:   Tue, 13 Sep 2022 16:07:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, stable <stable@...nel.org>,
        Nicolas Diaz <nicolas.diaz@....com>,
        Shenwei Wang <shenwei.wang@....com>
Subject: [PATCH 4.9 04/42] serial: fsl_lpuart: RS485 RTS polariy is inverse

From: Shenwei Wang <shenwei.wang@....com>

commit 846651eca073e2e02e37490a4a52752415d84781 upstream.

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")
Cc: stable <stable@...nel.org>
Signed-off-by: Nicolas Diaz <nicolas.diaz@....com>
Signed-off-by: Shenwei Wang <shenwei.wang@....com>
Link: https://lore.kernel.org/r/20220805144529.604856-1-shenwei.wang@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/tty/serial/fsl_lpuart.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -951,9 +951,9 @@ static int lpuart_config_rs485(struct ua
 		 * 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;
 	}
 
 	/* Store the new configuration */