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 <[email protected]> > --- > 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 [email protected] http://lists.infradead.org/mailman/listinfo/barebox
