linux-kernel - [PATCH v1] serial: imx: set receiver level before starting uart

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Date: Fri, 21 Jun 2024 17:37:49 +0200
From: Stefan Eichenberger <eichest@...il.com>
To: gregkh@...uxfoundation.org,
	jirislaby@...nel.org,
	shawnguo@...nel.org,
	s.hauer@...gutronix.de,
	kernel@...gutronix.de,
	festevam@...il.com,
	l.sanfilippo@...bus.com,
	cniedermaier@...electronics.com,
	john.ogness@...utronix.de,
	esben@...nix.com,
	rickaran@...s.com,
	tglx@...utronix.de,
	stefan@...er.ch,
	francesco.dolcini@...adex.com
Cc: linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	Stefan Eichenberger <stefan.eichenberger@...adex.com>
Subject: [PATCH v1] serial: imx: set receiver level before starting uart

From: Stefan Eichenberger <stefan.eichenberger@...adex.com>

Set the receiver level to something > 0 before calling imx_uart_start_rx
in rs485_config. This is necessary to avoid an interrupt storm that
might prevent the system from booting. This was seen on an i.MX7 device
when the rs485-rts-active-low property was active in the device tree.

Fixes: 6d215f83e5fc ("serial: imx: warn user when using unsupported configuration")
Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
---
 drivers/tty/serial/imx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 2eb22594960f3..f4f40c9373c2f 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1952,8 +1952,10 @@ static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termio
 
 	/* Make sure Rx is enabled in case Tx is active with Rx disabled */
 	if (!(rs485conf->flags & SER_RS485_ENABLED) ||
-	    rs485conf->flags & SER_RS485_RX_DURING_TX)
+	    rs485conf->flags & SER_RS485_RX_DURING_TX) {
+		imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
 		imx_uart_start_rx(port);
+	}
 
 	return 0;
 }
-- 
2.43.0