[PATCH 3/5] serial: core: Support common rs485 binding for RTS polarity

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When a driver invokes the uart_get_rs485_mode() helper, set the RTS
polarity to active high by default unless the newly introduced
"rs485-rts-active-low" property was specified.

omap-serial historically defaults to active low and supports an
"rs485-rts-active-high" property to inverse the polarity.  Retain that
behavior for compatibility.

Cc: Mark Jackson <mpfj@xxxxxxxxxxxxx>
Cc: Michał Oleszczyk <oleszczyk.m@xxxxxxxxx>
Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
Cc: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
---
 drivers/tty/serial/omap-serial.c | 7 +++++--
 drivers/tty/serial/serial_core.c | 8 ++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index e6aadb6d02e5..7ef36c0af825 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1617,10 +1617,13 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 
 	uart_get_rs485_mode(up->dev, rs485conf);
 
-	if (of_property_read_bool(np, "rs485-rts-active-high"))
+	if (of_property_read_bool(np, "rs485-rts-active-high")) {
 		rs485conf->flags |= SER_RS485_RTS_ON_SEND;
-	else
+		rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
+	} else {
+		rs485conf->flags &= ~SER_RS485_RTS_ON_SEND;
 		rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
+	}
 
 	/* check for tx enable gpio */
 	up->rts_gpio = of_get_named_gpio_flags(np, "rts-gpio", 0, &flags);
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 548bb80223c1..64e15507a9bd 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3048,6 +3048,14 @@ void uart_get_rs485_mode(struct device *dev, struct serial_rs485 *rs485conf)
 		rs485conf->delay_rts_after_send = 0;
 	}
 
+	if (device_property_read_bool(dev, "rs485-rts-active-low")) {
+		rs485conf->flags &= ~SER_RS485_RTS_ON_SEND;
+		rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
+	} else {
+		rs485conf->flags |= SER_RS485_RTS_ON_SEND;
+		rs485conf->flags &= ~SER_RS485_RTS_AFTER_SEND;
+	}
+
 	/*
 	 * clear full-duplex and enabled flags to get to a defined state with
 	 * the two following properties.
-- 
2.11.0

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