From 703a290a6b350b6fb148b39382a4aff1f321e012 Mon Sep 17 00:00:00 2001
From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Date: Fri, 16 Feb 2024 23:47:07 +0100
Subject: [PATCH] serial: stm32: do not always set SER_RS485_RX_DURING_TX if
 RS485 is enabled

References: bsc#1214683 (PREEMPT_RT prerequisite backports)
Patch-mainline: v6.6.19
Git-commit: f418ae73311deb901c0110b08d1bbafc20c1820e

commit f418ae73311deb901c0110b08d1bbafc20c1820e upstream.

Before commit 07c30ea5861f ("serial: Do not hold the port lock when setting
rx-during-tx GPIO") the SER_RS485_RX_DURING_TX flag was only set if the
rx-during-tx mode was not controlled by a GPIO. Now the flag is set
unconditionally when RS485 is enabled. This results in an incorrect setting
if the rx-during-tx GPIO is not asserted.

Fix this by setting the flag only if the rx-during-tx mode is not
controlled by a GPIO and thus restore the correct behaviour.

Cc: stable@vger.kernel.org # 6.6+
Fixes: 07c30ea5861f ("serial: Do not hold the port lock when setting rx-during-tx GPIO")
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240216224709.9928-1-l.sanfilippo@kunbus.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 drivers/tty/serial/stm32-usart.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index b6f4f436a565..e5f933beb6c0 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -251,7 +251,9 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
 		writel_relaxed(cr3, port->membase + ofs->cr3);
 		writel_relaxed(cr1, port->membase + ofs->cr1);
 
-		rs485conf->flags |= SER_RS485_RX_DURING_TX;
+		if (!port->rs485_rx_during_tx_gpio)
+			rs485conf->flags |= SER_RS485_RX_DURING_TX;
+
 	} else {
 		stm32_usart_clr_bits(port, ofs->cr3,
 				     USART_CR3_DEM | USART_CR3_DEP);