raspberrypi."4": add DigiAMP+ overlay

raspberry-pi/4/default.nix

@@ -15,6 +15,7 @@
     ./pwm0.nix
     ./pkgs-overlays.nix
     ./xhci.nix
+    ./digi-amp-plus.nix
   ];
 
   boot = {

raspberry-pi/4/digi-amp-plus.nix

@@ -0,0 +1,93 @@
+{ config, lib, ... }:
+
+let
+  cfg = config.hardware.raspberry-pi."4".digi-amp-plus;
+in
+{
+  options.hardware = {
+    raspberry-pi."4".digi-amp-plus = {
+      enable = lib.mkEnableOption ''
+        support for the IQaudIO DigiAMP+ Hat.
+      '';
+
+      unmuteAmp = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        description = lib.mdDoc ''
+          "one-shot" unmute when kernel module first loads.
+        '';
+      };
+
+      autoMuteAmp = lib.mkOption {
+        type = lib.types.bool;
+        default = true;
+        description = lib.mdDoc ''
+          Unmute the amp when an ALSA device is opened by a client. Mute, with a five-second delay when the ALSA device is closed.
+          (Reopening the device within the five-second close window will cancel mute.)
+        '';
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    hardware.raspberry-pi."4".apply-overlays-dtmerge.enable = lib.mkDefault true;
+
+    hardware.deviceTree = {
+      overlays = [
+        # Adapted from to: https://github.com/raspberrypi/linux/blob/3ed6d34d53e94ecbebc64c8fa3d1b6d3c41db8fb/arch/arm/boot/dts/overlays/iqaudio-dacplus-overlay.dts
+        # changes:
+        # - modified top-level "compatible" field from bcm2835 to bcm2711
+        # - s/i2s_clk_producer/i2s/ (name on bcm2711 platform)
+        {
+          name = "iqaudio-digiampplus-overlay";
+          dtsText = ''
+            /dts-v1/;
+            /plugin/;
+
+            / {
+              compatible = "brcm,bcm2711";
+
+              fragment@0 {
+                target = <&i2s>;
+                __overlay__ {
+                  status = "okay";
+                };
+              };
+
+              fragment@1 {
+                target = <&i2c1>;
+                __overlay__ {
+                  #address-cells = <1>;
+                  #size-cells = <0>;
+                  status = "okay";
+
+                  pcm5122@4c {
+                    #sound-dai-cells = <0>;
+                    compatible = "ti,pcm5122";
+                    reg = <0x4c>;
+                    AVDD-supply = <&vdd_3v3_reg>;
+                    DVDD-supply = <&vdd_3v3_reg>;
+                    CPVDD-supply = <&vdd_3v3_reg>;
+                    status = "okay";
+                  };
+                };
+              };
+
+              fragment@2 {
+                target = <&sound>;
+                iqaudio_dac: __overlay__ {
+                  compatible = "iqaudio,iqaudio-dac";
+                  i2s-controller = <&i2s>;
+                  mute-gpios = <&gpio 22 0>;
+                  status = "okay";
+                  ${lib.optionalString cfg.unmuteAmp "iqaudio-dac,unmute-amp;"}
+                  ${lib.optionalString cfg.autoMuteAmp "iqaudio-dac,auto-mute-amp;"}
+                };
+              };
+            };
+          '';
+        }
+      ];
+    };
+  };
+}