From: Fabio Estevam <fabio.estevam@xxxxxxx>
On a board that needs to drive RTS GPIO high in order to enable the
transmission of a RS485 transceiver the following description is
passed in the devide tree:
&uart4 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_uart4>;
rts-gpios = <&gpio6 2 GPIO_ACTIVE_HIGH>;
status = "okay";
};
and userspace configures the uart port as follows:
/* enable RS485 mode: */
rs485conf.flags |= SER_RS485_ENABLED;
/* set logical level for RTS pin equal to 1 when sending: */
rs485conf.flags |= SER_RS485_RTS_ON_SEND;
/* set logical level for RTS pin equal to 0 after sending: */
rs485conf.flags &= ~(SER_RS485_RTS_AFTER_SEND);
However the RTS GPIO polarity observed in the oscilloscope is inverted.
When the SER_RS485_RTS_ON_SEND flag is set the imx_port_rts_active()
function should be called and following the same logic when
SER_RS485_RTS_AFTER_SEND flag is cleared the imx_port_rts_inactive()
should be called.
Do such logic change so that RS485 communication in half duplex can
work successfully when the RTS GPIO pin is passed via device tree.
Signed-off-by: Fabio Estevam <fabio.estevam@xxxxxxx>
---
drivers/tty/serial/imx.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 33fcc84..29dd57c 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -377,9 +377,9 @@ static void imx_stop_tx(struct uart_port *port)
readl(port->membase + USR2) & USR2_TXDC) {
temp = readl(port->membase + UCR2);
if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
- imx_port_rts_inactive(sport, &temp);
- else
imx_port_rts_active(sport, &temp);
+ else
+ imx_port_rts_inactive(sport, &temp);
temp |= UCR2_RXEN;
writel(temp, port->membase + UCR2);
@@ -585,9 +585,9 @@ static void imx_start_tx(struct uart_port *port)
if (port->rs485.flags & SER_RS485_ENABLED) {
temp = readl(port->membase + UCR2);
if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
- imx_port_rts_inactive(sport, &temp);
- else
imx_port_rts_active(sport, &temp);
+ else
+ imx_port_rts_inactive(sport, &temp);
if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
temp &= ~UCR2_RXEN;
writel(temp, port->membase + UCR2);
@@ -1477,9 +1477,9 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
*/
if (port->rs485.flags &
SER_RS485_RTS_AFTER_SEND)
- imx_port_rts_inactive(sport, &ucr2);
- else
imx_port_rts_active(sport, &ucr2);
+ else
+ imx_port_rts_inactive(sport, &ucr2);
} else {
imx_port_rts_auto(sport, &ucr2);
}
@@ -1489,9 +1489,9 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
} else if (port->rs485.flags & SER_RS485_ENABLED) {
/* disable transmitter */
if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
- imx_port_rts_inactive(sport, &ucr2);
- else
imx_port_rts_active(sport, &ucr2);
+ else
+ imx_port_rts_inactive(sport, &ucr2);
}
@@ -1733,9 +1733,9 @@ static int imx_rs485_config(struct uart_port *port,
/* disable transmitter */
temp = readl(sport->port.membase + UCR2);
if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND)
- imx_port_rts_inactive(sport, &temp);
- else
imx_port_rts_active(sport, &temp);
+ else
+ imx_port_rts_inactive(sport, &temp);
writel(temp, sport->port.membase + UCR2);
}
--
2.7.4
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
