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serial: stm32: do not deassert RS485 RTS GPIO prematurely

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commit 2790ce2395 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: d7c7671616 ("serial: stm32: Use TC interrupt to deassert GPIO RTS in RS485 mode")
Cc: stable <stable@kernel.org>
Signed-off-by: Cheick Traore <cheick.traore@foss.st.com>
Link: https://lore.kernel.org/r/20250320152540.709091-1-cheick.traore@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Cheick Traore
2025-03-20 16:25:40 +01:00
committed by Greg Kroah-Hartman
parent f869075830
commit 5f9176f82e
1 changed files with 1 additions and 3 deletions
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drivers/tty/serial/stm32-usart.c
+1 -3
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@@ -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);