From 99f2ab0dad947049e0fa62e88c1e4c1feb7ab379 Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Thu, 4 Feb 2021 14:41:10 +0000
Subject: [PATCH] dtoverlays: Add an overlay for the VGA666 when used
 with vc4-kms-v3d

Includes optional use of GPIOs 0&1 / BSC0 for DDC to read the EDID
from the display.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
 arch/arm/boot/dts/overlays/Makefile           |   1 +
 arch/arm/boot/dts/overlays/README             |  10 ++
 .../dts/overlays/vc4-kms-vga666-overlay.dts   | 100 ++++++++++++++++++
 3 files changed, 111 insertions(+)
 create mode 100644 arch/arm/boot/dts/overlays/vc4-kms-vga666-overlay.dts

--- a/arch/arm/boot/dts/overlays/Makefile
+++ b/arch/arm/boot/dts/overlays/Makefile
@@ -211,6 +211,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	vc4-kms-kippah-7inch.dtbo \
 	vc4-kms-v3d.dtbo \
 	vc4-kms-v3d-pi4.dtbo \
+	vc4-kms-vga666.dtbo \
 	vga666.dtbo \
 	w1-gpio.dtbo \
 	w1-gpio-pullup.dtbo \
--- a/arch/arm/boot/dts/overlays/README
+++ b/arch/arm/boot/dts/overlays/README
@@ -3120,10 +3120,20 @@ Params: cma-512                 CMA is 5
                                 outputs)
 
 
+Name:   vc4-kms-vga666
+Info:   Enable the VGA666 (resistor ladder ADC) for the vc4-kms-v3d driver.
+        Requires vc4-kms-v3d to be loaded.
+Load:   dtoverlay=vc4-kms-vga666,<param>
+Params: ddc                     Enables GPIOs 0&1 as the I2C to read the EDID
+                                from the display. NB These are NOT 5V tolerant
+                                GPIOs, therefore level shifters are required.
+
+
 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.
+        NOT for use with vc4-kms-v3d.
 Load:   dtoverlay=vga666
 Params: <None>
 
--- /dev/null
+++ b/arch/arm/boot/dts/overlays/vc4-kms-vga666-overlay.dts
@@ -0,0 +1,100 @@
+/*
+ * vc4-kms-vga666-overlay.dts
+ * Configures a FenLogic or similar VGA666 DPI adapter when using the
+ * vc4-kms-v3d driver.
+ * If a suitable I2C level shifter is connected to GPIOs 0&1 and the VGA
+ * ID1/SDA (pin 12) and ID3/SCL (pin 15) lines, then there is the option to
+ * enable reading the EDID from the display.
+ */
+
+/dts-v1/;
+/plugin/;
+
+#include <dt-bindings/pinctrl/bcm2835.h>
+
+/ {
+	compatible = "brcm,bcm2835";
+
+	fragment@0 {
+		target-path = "/";
+		__overlay__ {
+			vga_connector: vga_connector {
+				compatible = "vga-connector";
+				label = "vga";
+
+				port {
+					vga_con_in: endpoint {
+						remote-endpoint = <&vga666_out>;
+					};
+				};
+			};
+
+			vga_dac {
+				compatible = "dumb-vga-dac";
+
+				ports {
+					#address-cells = <1>;
+					#size-cells = <0>;
+
+					port@0 {
+						reg = <0>;
+
+						vga666_in: endpoint {
+							remote-endpoint = <&dpi_out>;
+						};
+					};
+
+					port@1 {
+						reg = <1>;
+
+						vga666_out: endpoint {
+							remote-endpoint = <&vga_con_in>;
+						};
+					};
+				};
+			};
+
+		};
+	};
+
+	fragment@1 {
+		target = <&dpi>;
+		__overlay__  {
+			status = "okay";
+
+			pinctrl-names = "default";
+			pinctrl-0 = <&dpi_18bit_gpio2>;
+
+			port {
+				dpi_out: endpoint@0 {
+					remote-endpoint = <&vga666_in>;
+				};
+			};
+		};
+	};
+
+	fragment@2 {
+		target = <&vga_connector>;
+		__dormant__  {
+			ddc-i2c-bus = <&i2c_vc>;
+		};
+	};
+
+	fragment@3 {
+		target = <&i2c0if>;
+		__dormant__ {
+			status = "okay";
+		};
+	};
+
+	fragment@4 {
+		target = <&i2c0mux>;
+		__dormant__ {
+			status = "okay";
+		};
+	};
+
+	__overrides__ {
+		ddc = <0>,"=2", <0>,"=3", <0>,"=4";
+	};
+};