linux-kernel - [RESEND PATCH v4 7/7] serial: 8250_exar: Set missing rs485

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Date:   Sun, 19 Nov 2023 12:28:55 +0100
From:   Lino Sanfilippo <l.sanfilippo@...bus.com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        ilpo.jarvinen@...ux.intel.com
Cc:     u.kleine-koenig@...gutronix.de, shawnguo@...nel.org,
        s.hauer@...gutronix.de, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, cniedermaier@...electronics.com,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        LinoSanfilippo@....de, lukas@...ner.de, p.rosenberger@...bus.com,
        Lino Sanfilippo <l.sanfilippo@...bus.com>,
        stable@...r.kernel.org
Subject: [RESEND PATCH v4 7/7] serial: 8250_exar: Set missing rs485_supported flag

The UART supports an auto-RTS mode in which the RTS pin is automatically
activated during transmission. So mark this mode as being supported even
if RTS is not controlled by the driver but the UART.

Also the serial core expects now at least one of both modes rts-on-send or
rts-after-send to be supported. This is since during sanitization
unsupported flags are deleted from a RS485 configuration set by userspace.
However if the configuration ends up with both flags unset, the core prints
a warning since it considers such a configuration invalid (see
uart_sanitize_serial_rs485()).

Cc: stable@...r.kernel.org
Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
---
 drivers/tty/serial/8250/8250_exar.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
index 6085d356ad86..23366f868ae3 100644
--- a/drivers/tty/serial/8250/8250_exar.c
+++ b/drivers/tty/serial/8250/8250_exar.c
@@ -480,7 +480,7 @@ static int sealevel_rs485_config(struct uart_port *port, struct ktermios *termio
 }
 
 static const struct serial_rs485 generic_rs485_supported = {
-	.flags = SER_RS485_ENABLED,
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND,
 };
 
 static const struct exar8250_platform exar8250_default_platform = {
@@ -524,7 +524,8 @@ static int iot2040_rs485_config(struct uart_port *port, struct ktermios *termios
 }
 
 static const struct serial_rs485 iot2040_rs485_supported = {
-	.flags = SER_RS485_ENABLED | SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
+	.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND |
+		 SER_RS485_RX_DURING_TX | SER_RS485_TERMINATE_BUS,
 };
 
 static const struct property_entry iot2040_gpio_properties[] = {
-- 
2.42.0