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 @@ -509,7 +509,7 @@ static void stm32_start_tx(struct uart_p { struct circ_buf *xmit = &port->state->xmit; - if (uart_circ_empty(xmit)) + if (uart_circ_empty(xmit) && !port->x_char) return; stm32_transmit_chars(port);