linux-kernel - [PATCH v2 6/7] serial: core, imx: do not set RS485 enabled if it is not supported

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Date:   Wed, 11 Oct 2023 19:38:28 +0200
From:   Lino Sanfilippo <l.sanfilippo@...bus.com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        ilpo.jarvinen@...ux.intel.com
Cc:     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,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: [PATCH v2 6/7] serial: core, imx: do not set RS485 enabled if it is not supported

If the imx driver cannot support RS485 it sets the ports rs485_supported
structure to NULL. But it still calls uart_get_rs485_mode() which may set
the RS485_ENABLED flag nevertheless.

This may lead to an attempt to configure RS485 even if it is not supported
when the flag is evaluated in uart_configure_port() at port startup.

Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED
flag is not supported by the caller.

With this fix a check for RTS availability is now obsolete in the imx
driver, since it can not evaluate to true any more. Remove this check, too.

Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported")
Cc: stable@...r.kernel.org
Suggested-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
---
 drivers/tty/serial/imx.c         | 4 ----
 drivers/tty/serial/serial_core.c | 3 +++
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index edb2ec6a5567..c8c19bf8585d 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2332,10 +2332,6 @@ static int imx_uart_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	if (sport->port.rs485.flags & SER_RS485_ENABLED &&
-	    (!sport->have_rtscts && !sport->have_rtsgpio))
-		dev_err(&pdev->dev, "no RTS control, disabling rs485\n");
-
 	/*
 	 * If using the i.MX UART RTS/CTS control then the RTS (CTS_B)
 	 * signal cannot be set low during transmission in case the
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index dca09877fabc..95cec2343b35 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3576,6 +3576,9 @@ int uart_get_rs485_mode(struct uart_port *port)
 	int ret;
 	int rx_during_tx_gpio_flag;
 
+	if (!(port->rs485_supported.flags & SER_RS485_ENABLED))
+		return 0;
+
 	ret = device_property_read_u32_array(dev, "rs485-rts-delay",
 					     rs485_delay, 2);
 	if (!ret) {
-- 
2.40.1