Re: [PATCH 07/10] arm64: dts: imx8mp-skov: configure uart1 for RS485

[Frank Li <Frank.li@nxp.com>]

On Thu, Dec 19, 2024 at 08:25:31AM +0100, Ahmad Fatoum wrote:
> uart1 TX, RX and RTS signals go off the base board and to a RS485
> transceiver. Describe this in the device tree.

Look like it is not related what your did in this patch.

Add uart-has-rtscts in uart1 to ... (because ....)

Frank
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi b/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi
> index 7ae686d37dda..bce23d62cd27 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi
> @@ -404,6 +404,13 @@ &uart1 {
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_uart1>;
>  	status = "okay";
> +	/*
> +	 * While there is no CTS line, the property "uart-has-rtscts" is still
> +	 * the right thing to do to enable the UART to do RS485. In RS485-Mode
> +	 * CTS isn't used anyhow and there is no dedicated property
> +	 * "uart-has-rts-but-no-cts".
> +	 */
> +	uart-has-rtscts;
>  };
>
>  &uart2 {
> @@ -618,6 +625,8 @@ pinctrl_uart1: uart1grp {
>  			MX8MP_IOMUXC_UART1_RXD__UART1_DCE_RX			0x140
>  			MX8MP_IOMUXC_UART1_TXD__UART1_DCE_TX			0x140
>  			MX8MP_IOMUXC_UART3_RXD__UART1_DTE_RTS			0x140
> +			/* CTS pin is not connected, but needed as workaround */

what' means here! what's problem to be workaround?

> +			MX8MP_IOMUXC_UART3_TXD__UART1_DTE_CTS			0x140
>  		>;
>  	};
>
>
> --
> 2.39.5
>