serial: stm32: Add support for rs485 RX_DURING_TX output GPIO

If a RX_DURING_TX GPIO is defined by the DT property "rs485-rx-during-tx-gpios"
this patch switches this GPIO accordingly to the RS485 flag RX_DURING_TX in user
space. Controlled by this GPIO, now the hardware is responsible for connecting
or disconnecting RX during TX.

Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Link: https://lore.kernel.org/r/20221202104127.122761-4-cniedermaier@dh-electronics.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index a1490033aa164b77ae884e34749fab32d28fe511..f1b1df78118f6ffa4d04659d55140fa9db731927 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -226,7 +226,11 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
 
        stm32_usart_clr_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
 
-       rs485conf->flags |= SER_RS485_RX_DURING_TX;
+       if (port->rs485_rx_during_tx_gpio)
+               gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
+                                        !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
+       else
+               rs485conf->flags |= SER_RS485_RX_DURING_TX;
 
        if (rs485conf->flags & SER_RS485_ENABLED) {
                cr1 = readl_relaxed(port->membase + ofs->cr1);