linux-kernel - [PATCH] serial: imx: allow CRTSCTS with RTS/CTS GPIOs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251016113730.245341-1-matthias.schiffer@ew.tq-group.com>
Date: Thu, 16 Oct 2025 13:37:30 +0200
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>
Cc: Fabio Estevam <festevam@...il.com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux@...tq-group.com,
	Matthias Schiffer <matthias.schiffer@...tq-group.com>
Subject: [PATCH] serial: imx: allow CRTSCTS with RTS/CTS GPIOs

The CTS GPIO is only evaluated when the CRTSCTS termios flag is enabled;
it should be possible to enable the flag when only GPIO and no hardware-
controlled RTS/CTS are available. UCR2_IRTS is kept enabled in this case,
so the hardware CTS is ignored.

Fixes: 58362d5be352 ("serial: imx: implement handshaking using gpios with the mctrl_gpio helper")
Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
---
 drivers/tty/serial/imx.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 500dfc009d03e..4a54a689a0603 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1117,8 +1117,8 @@ static void imx_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
 			ucr2 |= UCR2_CTS;
 			/*
 			 * UCR2_IRTS is unset if and only if the port is
-			 * configured for CRTSCTS, so we use inverted UCR2_IRTS
-			 * to get the state to restore to.
+			 * configured for hardware-controlled CRTSCTS, so we use
+			 * inverted UCR2_IRTS to get the state to restore to.
 			 */
 			if (!(ucr2 & UCR2_IRTS))
 				ucr2 |= UCR2_CTSC;
@@ -1780,7 +1780,7 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 	if ((termios->c_cflag & CSIZE) == CS8)
 		ucr2 |= UCR2_WS;
 
-	if (!sport->have_rtscts)
+	if (!sport->have_rtscts && !sport->have_rtsgpio)
 		termios->c_cflag &= ~CRTSCTS;
 
 	if (port->rs485.flags & SER_RS485_ENABLED) {
@@ -1794,7 +1794,7 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 		else
 			imx_uart_rts_inactive(sport, &ucr2);
 
-	} else if (termios->c_cflag & CRTSCTS) {
+	} else if ((termios->c_cflag & CRTSCTS) && sport->have_rtscts) {
 		/*
 		 * Only let receiver control RTS output if we were not requested
 		 * to have RTS inactive (which then should take precedence).
@@ -1803,7 +1803,7 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
 			ucr2 |= UCR2_CTSC;
 	}
 
-	if (termios->c_cflag & CRTSCTS)
+	if ((termios->c_cflag & CRTSCTS) && sport->have_rtscts)
 		ucr2 &= ~UCR2_IRTS;
 	if (termios->c_cflag & CSTOPB)
 		ucr2 |= UCR2_STPB;
-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/