arm64: dts: imx8mp-skov: configure uart1 for RS485

uart1 TX, RX and RTS signals go off the base board and to a RS485
transceiver. Describe this in the device tree.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

diff --git a/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi b/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi
index 5e3a7c859c6612fbe7d4c3b69c60c4a898550ff5..c65fbadd5db3f38eae398e019fee5c20eeec3f64 100644 (file)
--- a/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mp-skov-reva.dtsi
@@ -403,6 +403,13 @@ &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 {
@@ -616,6 +623,8 @@ 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 */
+                       MX8MP_IOMUXC_UART3_TXD__UART1_DTE_CTS                   0x140
                >;
        };