[PATCH 4.19 10/86] serial: stm32: fix software flow control transfer

Greg Kroah-Hartman
2022-02-07T11:23:14Z

From: Valentin Caron <valentin.caron@foss.st.com>

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@vger.kernel.org>
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20220111164441.6178-3-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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);