[PATCH 4/4] serial: stm32: Add support for rs485 RX_DURING_TX GPIO

[Christoph Niedermaier]

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 at dh-electronics.com>
---
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Jiri Slaby <jirislaby at kernel.org>
Cc: Maxime Coquelin <mcoquelin.stm32 at gmail.com>
Cc: Alexandre Torgue <alexandre.torgue at foss.st.com>
Cc: Marek Vasut <marex at denx.de>
Cc: linux-stm32 at st-md-mailman.stormreply.com
To: linux-serial at vger.kernel.org
To: linux-arm-kernel at lists.infradead.org
---
 drivers/tty/serial/stm32-usart.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index dfdbcf092fac..91ff6d386932 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -226,7 +226,14 @@ 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) {
+		if (rs485conf->flags & SER_RS485_RX_DURING_TX)
+			gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio, 1);
+		else
+			gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio, 0);
+	} else {
+		rs485conf->flags |= SER_RS485_RX_DURING_TX;
+	}
 
 	if (rs485conf->flags & SER_RS485_ENABLED) {
 		cr1 = readl_relaxed(port->membase + ofs->cr1);
-- 
2.11.0