ARM: dts: kirkwood: provide template for RS-232/485 configuration for OpenRD

Some OpenRD boards have RS-232 and RS-486 connectors wired, but using them
needs a custom DTB as the current DTB configures SD card slot instead.

This patch adds documentation into the DTS on how to change
the configuration.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

diff --git a/arch/arm/boot/dts/kirkwood-openrd.dtsi b/arch/arm/boot/dts/kirkwood-openrd.dtsi
index f65b7273bb0aa792203c938f0871965c448826e6..24f1d30970a0650b535bcd67395c0cea8ace7935 100644 (file)
--- a/arch/arm/boot/dts/kirkwood-openrd.dtsi
+++ b/arch/arm/boot/dts/kirkwood-openrd.dtsi
@@ -40,7 +40,7 @@
                        pinctrl-0 = <&pmx_select28 &pmx_sdio_cd &pmx_select34>;
                        pinctrl-names = "default";
 
-                       pmx_select28: pmx-select-rs232-rs484 {
+                       pmx_select28: pmx-select-rs232-rs485 {
                                marvell,pins = "mpp28";
                                marvell,function = "gpio";
                        };
@@ -65,10 +65,39 @@
                        status = "okay";
                        cd-gpios = <&gpio0 29 9>;
                };
+               gpio@10100 {
+                       p28 {
+                               gpio-hog;
+                               gpios = <28 GPIO_ACTIVE_HIGH>;
+                               /*
+                                * SelRS232or485 selects between RS-232 or RS-485
+                                * mode for the second UART.
+                                *
+                                * Low: RS-232
+                                * High: RS-485
+                                *
+                                * To use the second UART, you need to change also
+                                * the SelUARTorSD.
+                                */
+                               output-low;
+                               line-name = "SelRS232or485";
+                       };
+               };
                gpio@10140 {
                        p2 {
                                gpio-hog;
                                gpios = <2 GPIO_ACTIVE_HIGH>;
+                               /*
+                                * SelUARTorSD selects between the second UART
+                                * (serial@12100) and SD (mvsdio@90000).
+                                *
+                                * Low: UART
+                                * High: SD
+                                *
+                                * When changing this line make sure the newly
+                                * selected device node is enabled and the
+                                * previously selected device node is disabled.
+                                */
                                output-high; /* Select SD by default */
                                line-name = "SelUARTorSD";
                        };