linux-kernel - [PATCH] serial: xilinx_uartps: fix rs485 initialization at boot

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Message-Id: <20251216152641.196221-1-jakub.turek@elsta.tech>
Date: Tue, 16 Dec 2025 16:26:41 +0100
From: "j.turek" <jakub.turek@...ta.tech>
To: gregkh@...uxfoundation.org,
	jirislaby@...nel.org
Cc: michal.simek@....com,
	namcao@...utronix.de,
	tglx@...utronix.de,
	zack.rusin@...adcom.com,
	sean.anderson@...ux.dev,
	hshah@...ado.com,
	linux-serial@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	"j.turek" <jakub.turek@...ta.tech>
Subject: [PATCH] serial: xilinx_uartps: fix rs485 initialization at boot

When 'linux,rs485-enabled-at-boot-time;' property is enabled in device-tree
and there is no rts-gpio defined there is NULL pointer dereference in
function 'cdns_rts_gpio_enable' because 'cdns_uart->port->membase' pointer
is not set at this point

Signed-off-by: Jakub Turek <jakub.turek@...ta.tech>

Fixes: fccc9d9233f9 ("tty: serial: uartps: Add rs485 support to uartps driver")
---
 drivers/tty/serial/xilinx_uartps.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index c793fc74c26b..1e4d54fd5762 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1816,8 +1816,6 @@ static int cdns_uart_probe(struct platform_device *pdev)
 		console_port = port;
 	}
 #endif
-	if (cdns_uart_data->port->rs485.flags & SER_RS485_ENABLED)
-		cdns_rs485_rx_setup(cdns_uart_data);
 
 	rc = uart_add_one_port(&cdns_uart_uart_driver, port);
 	if (rc) {
@@ -1826,6 +1824,9 @@ static int cdns_uart_probe(struct platform_device *pdev)
 		goto err_out_pm_disable;
 	}
 
+	if (cdns_uart_data->port->rs485.flags & SER_RS485_ENABLED)
+		cdns_rs485_rx_setup(cdns_uart_data);
+
 #ifdef CONFIG_SERIAL_XILINX_PS_UART_CONSOLE
 	/* This is not port which is used for console that's why clean it up */
 	if (console_port == port &&
-- 
2.34.1