nixpkgs/nixos/modules/installer/sd-card/sd-image-aarch64.nix

# To build, use:
# nix-build nixos -I nixos-config=nixos/modules/installer/sd-card/sd-image-aarch64.nix -A config.system.build.sdImage
{ config, lib, pkgs, ... }:

{
  imports = [
    ../../profiles/base.nix
    ./sd-image.nix
  ];

  boot.loader.grub.enable = false;
  boot.loader.generic-extlinux-compatible.enable = true;

  boot.consoleLogLevel = lib.mkDefault 7;

  # The serial ports listed here are:
  # - ttyS0: for Tegra (Jetson TX1)
  # - ttyAMA0: for QEMU's -machine virt
  boot.kernelParams = ["console=ttyS0,115200n8" "console=ttyAMA0,115200n8" "console=tty0"];

  boot.initrd.availableKernelModules = [
    # Allows early (earlier) modesetting for the Raspberry Pi
    "vc4" "bcm2835_dma" "i2c_bcm2835"
    # Allows early (earlier) modesetting for Allwinner SoCs
    "sun4i_drm" "sun8i_drm_hdmi" "sun8i_mixer"
  ];

  sdImage = {
    populateFirmwareCommands = let
      configTxt = pkgs.writeText "config.txt" ''
        [pi3]
        kernel=u-boot-rpi3.bin

        [pi4]
        kernel=u-boot-rpi4.bin
        enable_gic=1
        armstub=armstub8-gic.bin

        # Otherwise the resolution will be weird in most cases, compared to
        # what the pi3 firmware does by default.
        disable_overscan=1

        [all]
        # Boot in 64-bit mode.
        arm_64bit=1

        # U-Boot needs this to work, regardless of whether UART is actually used or not.
        # Look in arch/arm/mach-bcm283x/Kconfig in the U-Boot tree to see if this is still
        # a requirement in the future.
        enable_uart=1

        # Prevent the firmware from smashing the framebuffer setup done by the mainline kernel
        # when attempting to show low-voltage or overtemperature warnings.
        avoid_warnings=1
      '';
      in ''
        (cd ${pkgs.raspberrypifw}/share/raspberrypi/boot && cp bootcode.bin fixup*.dat start*.elf $NIX_BUILD_TOP/firmware/)

        # Add the config
        cp ${configTxt} firmware/config.txt

        # Add pi3 specific files
        cp ${pkgs.ubootRaspberryPi3_64bit}/u-boot.bin firmware/u-boot-rpi3.bin

        # Add pi4 specific files
        cp ${pkgs.ubootRaspberryPi4_64bit}/u-boot.bin firmware/u-boot-rpi4.bin
        cp ${pkgs.raspberrypi-armstubs}/armstub8-gic.bin firmware/armstub8-gic.bin
        cp ${pkgs.raspberrypifw}/share/raspberrypi/boot/bcm2711-rpi-4-b.dtb firmware/
      '';
    populateRootCommands = ''
      mkdir -p ./files/boot
      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
    '';
  };
}