Add a config for Asus Zephyrus GA402X* (2023) series

- Disable power-saving for the keyboard on the Asus Zephyrus GA402X series (2023)
- Add more-aggressive roaming rules for Asus Mediatek cards when using IWD
  - Add note about potentially needing more-aggressive roaming rules for Asus Mediatek cards when using WPA-Supplicant
  - Make enabling the higher scanning optional
- Split-up the AMD-GPU and Nvidia configs
- Add switch for AMD-GPU recovery mode
- Add switch for AMD-GPU sg_display (Scatter/Gather) mode
- Add switch for AMD-GPU PSR support

asus/zephyrus/ga402x/amdgpu/default.nix

@@ -0,0 +1,58 @@
+{ config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  inherit (lib) mkDefault mkEnableOption mkIf mkMerge;
+  cfg = config.hardware.asus.zephyrus.ga402x;
+
+in {
+  imports = [
+    ../shared.nix
+  ];
+
+  options.hardware.asus.zephyrus.ga402x.amdgpu = {
+    recovery.enable = (mkEnableOption "Enable amdgpu.gpu_recovery kernel boot param") // { default = false; };
+    sg_display.enable = (mkEnableOption "Enable amdgpu.gpu_recovery kernel boot param") // { default = true; };
+    psr.enable = (mkEnableOption "Enable amdgpu.dcdebugmask=0x10 kernel boot param") // { default = true; };
+  };
+
+  config = mkMerge [
+    {
+      # AMD RX680
+      services.xserver.videoDrivers = mkDefault [ "amdgpu" ];
+
+      hardware = {
+        amdgpu.loadInInitrd = true;
+        opengl.extraPackages = with pkgs; [
+          vaapiVdpau
+          libvdpau-va-gl
+        ];
+      };
+    }
+
+    (mkIf cfg.amdgpu.recovery.enable {
+      # Hopefully fixes for where the kernel sometimes hangs when suspending or hibernating
+      #  (Though, I'm very suspicious of the Mediatek Wifi...)
+      boot.kernelParams = [
+        "amdgpu.gpu_recovery=1"
+      ];
+    })
+
+    (mkIf (!cfg.amdgpu.sg_display.enable) {
+      # Can help solve flickering/glitching display issues since Scatter/Gather code was reenabled
+      boot.kernelParams = [
+        "amdgpu.sg_display=0"
+      ];
+    })
+
+    (mkIf (!cfg.amdgpu.psr.enable) {
+      # Can help solve flickering/glitching display issues since Scatter/Gather code was reenabled
+      boot.kernelParams = [
+        "amdgpu.dcdebugmask=0x10"
+      ];
+    })
+  ];
+}

asus/zephyrus/ga402x/default.nix

@@ -0,0 +1,15 @@
+## When using from a Flake, you can access these via imports of the attr key, e.g:
+#
+# imports = [
+#   nixos-hardware.nixosModules.asus-zephyrus-ga402x.amdgpu
+# ];
+#
+## or:
+# imports = [
+#   nixos-hardware.nixosModules.asus-zephyrus-ga402x.nvidia
+# ];
+
+{
+  amdgpu = import ./amdgpu;
+  nvidia = import ./nvidia;
+}

asus/zephyrus/ga402x/nvidia/default.nix

@@ -0,0 +1,55 @@
+{ lib,
+  pkgs,
+  ...
+}:
+
+let
+  inherit (lib) mkDefault;
+
+in {
+  imports = [
+    ../shared.nix
+    ## "prime.nix" loads this, aleady:
+    # ../../../common/gpu/nvidia
+    ../../../../common/gpu/nvidia/prime.nix
+  ];
+
+  # NVIDIA GeForce RTX 4060 Mobile
+
+  boot = {
+    blacklistedKernelModules = [ "nouveau" ];
+  };
+
+  # Also in nvidia/default.nix
+  services.xserver.videoDrivers = mkDefault [ "nvidia" ];
+
+  hardware = {
+    ## Enable the Nvidia card, as well as Prime and Offload:
+    amdgpu.loadInInitrd = true;
+    opengl.extraPackages = with pkgs; [
+      # Also in nvidia/default.nix
+      vaapiVdpau
+      libvdpau-va-gl
+    ];
+
+    nvidia = {
+      modesetting.enable = true;
+      nvidiaSettings = true;
+
+      prime = {
+        offload = {
+          enable = true;
+          enableOffloadCmd = true;
+        };
+        amdgpuBusId = "PCI:101:0:0";
+        nvidiaBusId = "PCI:1:0:0";
+      };
+
+      powerManagement = {
+        # This is unreliable on the 4060;  works a few times, then hangs:
+        # enable = true;
+        # finegrained = true
+      };
+    };
+  };
+}

asus/zephyrus/ga402x/shared.nix

@@ -0,0 +1,76 @@
+{ config,
+  pkgs,
+  lib,
+  ...
+}:
+
+let
+  inherit (lib) mkDefault mkIf mkMerge version versionOlder;
+in {
+
+  imports = [
+    ../../../common/cpu/amd
+    # Better power-savings from AMD PState:
+    ../../../common/cpu/amd/pstate.nix
+    ../../../common/gpu/amd
+    ../../../common/pc/laptop
+    ../../../common/pc/laptop/acpi_call.nix
+    ../../../common/pc/ssd
+  ];
+
+  config = mkMerge [
+    {
+      # Configure basic system settings:
+      boot = {
+        kernelModules = [ "kvm-amd" ];
+        kernelParams = [
+          "mem_sleep_default=deep"
+          "pcie_aspm.policy=powersupersave"
+        ];
+      };
+
+      services = {
+        asusd = {
+          enable = mkDefault true;
+          enableUserService = mkDefault true;
+        };
+
+        supergfxd.enable = true;
+
+        udev = {
+          extraHwdb = ''
+            # Fixes mic mute button
+            evdev:name:*:dmi:bvn*:bvr*:bd*:svnASUS*:pn*:*
+            KEYBOARD_KEY_ff31007c=f20
+          '';
+          extraRules = ''
+            # Disable auto-suspend for the ASUS N-KEY Device, i.e. USB Keyboard
+            # Otherwise, it will tend to take 1-2 key-presses to wake-up after suspending
+            ACTION=="add", SUBSYSTEM=="usb", TEST=="power/autosuspend", ATTR{idVendor}=="0b05", ATTR{idProduct}=="19b6", ATTR{power/autosuspend}="-1"
+          '';
+        };
+      };
+    }
+
+    (mkIf (versionOlder version "23.11") {
+      # See https://asus-linux.org/wiki/nixos/ for info about some problems
+      # detecting the dGPU:
+      systemd.services.supergfxd.path = [ pkgs.pciutils ];
+    })
+
+    (mkIf (config.networking.wireless.iwd.enable && config.networking.wireless.scanOnLowSignal) {
+      # Meditek doesn't seem to be quite sensitive enough on the default roaming settings:
+      #   https://wiki.archlinux.org/title/Wpa_supplicant#Roaming
+      #   https://wiki.archlinux.org/title/Iwd#iwd_keeps_roaming
+      #
+      # But NixOS doesn't have the tweaks for IWD, yet.
+      networking.wireless.iwd.settings = {
+        General = {
+          RoamThreshold = -75;
+          RoamThreshold5G = -80;
+          RoamRetryInterval = 20;
+        };
+      };
+    })
+  ];
+}