Hi,
On 8/18/20 11:34 AM, Oleksij Rempel wrote:
> If we have a "linux,rs485-enabled-at-boot-time" DT property, we should
> set CTS flag as soon as possible to the active state. This will set an
> RS485 transmitter to receive-enable mode. Otherwise the RS485 bus will
> be blocked for entire system boot time and other bus participants will
> not be able to communicate.
(Sidenote: I'd have expected this to be done by pin configuration)
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
> drivers/serial/serial_imx.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/serial/serial_imx.c b/drivers/serial/serial_imx.c
> index c0265fc2d7..fe9b15d8b5 100644
> --- a/drivers/serial/serial_imx.c
> +++ b/drivers/serial/serial_imx.c
> @@ -60,6 +60,7 @@ struct imx_serial_priv {
> void __iomem *regs;
> struct clk *clk;
> struct imx_serial_devtype_data *devtype;
> + bool rs485_mode;
> };
>
> static int imx_serial_reffreq(struct imx_serial_priv *priv)
> @@ -107,6 +108,9 @@ static int imx_serial_init_port(struct console_device *cdev)
>
> /* Enable FIFOs */
> val = readl(regs + UCR2);
> + /* set CTS to not block RS485 bus */
> + if (priv->rs485_mode)
> + val |= UCR2_CTS;
jfyi: UCR2_CTS is without effect when UCR2_CTSC=1.
UCR2_CTSC is 0 on POR though, so I think it should be ok
to only touch UCR2_CTS
> val |= UCR2_SRST | UCR2_RXEN | UCR2_TXEN;
> writel(val, regs + UCR2);
>
> @@ -252,6 +256,10 @@ static int imx_serial_probe(struct device_d *dev)
> if (of_property_read_bool(dev->device_node, "fsl,dte-mode"))
> priv->dte_mode = 1;
>
> + if (of_property_read_bool(dev->device_node,
> + "linux,rs485-enabled-at-boot-time"))
> + priv->rs485_mode = 1;
You'll need to check rs485-rts-active-low absence as well, or you break
slave communication for other boards.
> +
> imx_serial_init_port(cdev);
>
> /* Enable UART */
>
--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
_______________________________________________
barebox mailing list
barebox@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/barebox
