BCM270X_DT: Overlay for the Fen Logic VGA666 board

The VGA666 board requires GPIOs 2-21 (so no I2C or UART). Using the
overlay (instead of a custom dt-blob.bin) has the advantage that it will
reserve those pins and stop other devices using them (except for GPIO),
but it does delay the point at which the output becomes valid until 2-3
seconds after the kernel has started.

Author: Phil Elwell

arch/arm/boot/dts/overlays/Makefile

@@ -43,6 +43,7 @@ dtb-$(RPI_DT_OVERLAYS) += spi-bcm2708-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += spi-bcm2835-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += tinylcd35-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += uart1-overlay.dtb
+dtb-$(RPI_DT_OVERLAYS) += vga666-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += w1-gpio-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += w1-gpio-pullup-overlay.dtb
 

arch/arm/boot/dts/overlays/README

@@ -497,6 +497,14 @@ Params: txd1_pin                 GPIO pin for TXD1 (14, 32 or 40 - default 14)
         rxd1_pin                 GPIO pin for RXD1 (15, 33 or 41 - default 15)
 
 
+Name:   vga666
+Info:   Overlay for the Fen Logic VGA666 board
+        This uses GPIOs 2-21 (so no I2C), and activates the output 2-3 seconds
+        after the kernel has started.
+Load:   dtoverlay=vga666
+Params: <None>
+
+
 Name:   w1-gpio
 Info:   Configures the w1-gpio Onewire interface module.
         Use this overlay if you *don't* need a GPIO to drive an external pullup.

arch/arm/boot/dts/overlays/vga666-overlay.dts

@@ -0,0 +1,30 @@
+/dts-v1/;
+/plugin/;
+
+/{
+	compatible = "brcm,bcm2708";
+
+	// There is no VGA driver module, but we need a platform device
+	// node (that doesn't already use pinctrl) to hang the pinctrl
+	// reference on - leds will do
+
+	fragment@0 {
+		target = <&leds>;
+		__overlay__ {
+			pinctrl-names = "default";
+			pinctrl-0 = <&vga666_pins>;
+		};
+	};
+
+	fragment@1 {
+		target = <&gpio>;
+		__overlay__ {
+			vga666_pins: vga666_pins {
+				brcm,pins = <2 3 4 5 6 7 8 9 10 11 12
+					     13 14 15 16 17 18 19 20 21>;
+				brcm,function = <6>; /* alt2 */
+				brcm,pull = <0>; /* no pull */
+			};
+		};
+	};
+};