| Message ID | 20230223042252.95480-2-marex@denx.de |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index bf51e2152dd5a..1e38fc9b10c11 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -693,8 +693,9 @@ static void stm32_usart_transmit_chars(struct uart_port *port) int ret; if (!stm32_port->hw_flow_control && - port->rs485.flags & SER_RS485_ENABLED) { - stm32_port->txdone = false; + port->rs485.flags & SER_RS485_ENABLED && + (port->x_char || + !(uart_circ_empty(xmit) || uart_tx_stopped(port)))) { stm32_usart_tc_interrupt_disable(port); stm32_usart_rs485_rts_enable(port); }
The stm32_usart_transmit_chars() may be called with empty or stopped transmit queue, and no XON/OFF character pending. This can happen at the end of transmission, where this last call is used to either handle the XON/XOFF x_char, or disable TX interrupt if queue is empty or stopped. If that occurs, do not assert the RS485 RTS/DE GPIO anymore, as the GPIO would remain asserted past the end of transmission and that would block the RS485 bus after the transmission. Only assert the RS485 RTS/DE GPIO if there is either pending XON/XOFF x_char, or at least one character in running transmit queue. Fixes: d7c76716169d ("serial: stm32: Use TC interrupt to deassert GPIO RTS in RS485 mode") Signed-off-by: Marek Vasut <marex@denx.de> --- Cc: Alexandre Torgue <alexandre.torgue@foss.st.com> Cc: Erwan Le Ray <erwan.leray@foss.st.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jean Philippe Romain <jean-philippe.romain@foss.st.com> Cc: Jiri Slaby <jirislaby@kernel.org> Cc: Johan Hovold <johan@kernel.org> Cc: Lukas Wunner <lukas@wunner.de> Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com> Cc: Valentin Caron <valentin.caron@foss.st.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-serial@vger.kernel.org Cc: linux-stm32@st-md-mailman.stormreply.com --- drivers/tty/serial/stm32-usart.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)