FAILED: patch "[PATCH] serial: stm32: do not deassert RS485 RTS GPIO prematurely" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 2790ce23951f0c497810c44ad60a126a59c8d84c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025040348-deem-hazard-b9f8@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2790ce23951f0c497810c44ad60a126a59c8d84c Mon Sep 17 00:00:00 2001
From: Cheick Traore <cheick.traore@foss.st.com>
Date: Thu, 20 Mar 2025 16:25:40 +0100
Subject: [PATCH] serial: stm32: do not deassert RS485 RTS GPIO prematurely

If stm32_usart_start_tx is called with an empty xmit buffer, RTS GPIO
could be deasserted prematurely, as bytes in TX FIFO are still
transmitting.
So this patch remove rts disable when xmit buffer is empty.

Fixes: d7c76716169d ("serial: stm32: Use TC interrupt to deassert GPIO RTS in RS485 mode")
Cc: stable <stable@kernel.org>
Signed-off-by: Cheick Traore <cheick.traore@foss.st.com>
Link: https://lore.kernel.org/r/20250320152540.709091-1-cheick.traore@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 4c97965ec43b..ad06b760cfca 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -965,10 +965,8 @@ static void stm32_usart_start_tx(struct uart_port *port)
 {
 	struct tty_port *tport = &port->state->port;
 
-	if (kfifo_is_empty(&tport->xmit_fifo) && !port->x_char) {
-		stm32_usart_rs485_rts_disable(port);
+	if (kfifo_is_empty(&tport->xmit_fifo) && !port->x_char)
 		return;
-	}
 
 	stm32_usart_rs485_rts_enable(port);