From 2790ce23951f0c497810c44ad60a126a59c8d84c Mon Sep 17 00:00:00 2001 From: Cheick Traore 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 Signed-off-by: Cheick Traore Link: https://lore.kernel.org/r/20250320152540.709091-1-cheick.traore@foss.st.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/stm32-usart.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) 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); -- 2.50.1