From 5f9176f82ec7d9f66f3892a330126de4ef66c2d6 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 commit 2790ce23951f0c497810c44ad60a126a59c8d84c upstream. 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 f5199fdecff2..9b9981352b1e 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);