This is a note to let you know that I've just added the patch titled serial: stm32: fix software flow control transfer to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: serial-stm32-fix-software-flow-control-transfer.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 037b91ec7729524107982e36ec4b40f9b174f7a2 Mon Sep 17 00:00:00 2001 From: Valentin Caron <valentin.caron@xxxxxxxxxxx> Date: Tue, 11 Jan 2022 17:44:41 +0100 Subject: serial: stm32: fix software flow control transfer From: Valentin Caron <valentin.caron@xxxxxxxxxxx> commit 037b91ec7729524107982e36ec4b40f9b174f7a2 upstream. x_char is ignored by stm32_usart_start_tx() when xmit buffer is empty. Fix start_tx condition to allow x_char to be sent. Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver") Cc: stable <stable@xxxxxxxxxxxxxxx> Signed-off-by: Erwan Le Ray <erwan.leray@xxxxxxxxxxx> Signed-off-by: Valentin Caron <valentin.caron@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20220111164441.6178-3-valentin.caron@xxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/serial/stm32-usart.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -574,7 +574,7 @@ static void stm32_usart_start_tx(struct struct serial_rs485 *rs485conf = &port->rs485; struct circ_buf *xmit = &port->state->xmit; - if (uart_circ_empty(xmit)) + if (uart_circ_empty(xmit) && !port->x_char) return; if (rs485conf->flags & SER_RS485_ENABLED) { Patches currently in stable-queue which might be from valentin.caron@xxxxxxxxxxx are queue-5.10/serial-stm32-fix-software-flow-control-transfer.patch