On Mon, Jan 30, 2017 at 3:12 AM, Fabio Estevam <festevam@xxxxxxxxx> wrote:
> 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
>
Fabio,
Works great for me with respect to TXEN polarity thanks!
Something I noticed this time around while testing however is that in
some cases I'm not getting the dma_tx_callback telling us the tx dma
completed causing the stop_tx to return and the TXEN to not be
de-asserted. I hadn't noticed this before. Have you encountered it in
your use/testing?
Regards,
Tim
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