NixOS on ARM/Raspberry Pi 4

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Raspberry Pi 4 Family
(Image not available)
Manufacturer	Raspberry Pi Foundation
Architecture	AArch64
Bootloader	Custom or U-Boot
Boot order	Configurable; SD, USB, Netboot
Maintainer
Raspberry Pi 4B
SoC	BCM2711

The Raspberry Pi family of devices is a series of single-board computers made by the Raspberry Pi Foundation. They are all based on Broadcom System-on-a-chip (SOCs).

Status

Note: The Raspberry Pi 4 is currently unsupported though the NixOS distribution provides upstream beta-quality images.

The default Linux kernel in use, is the Raspberry Pi Foundation's fork. This will change for the mainline kernel once its support for the Raspberry Pi 4 Family is good enough to allow the user to boot, configure, and rebuild a system.

The Raspberry Pi 4 Family is only supported as AArch64. Use as armv7 is community supported.

Board-specific installation notes

First follow the generic installation steps to get the installer image and install using the installation and configuration steps.

Until the generic image works, a temporary device-specific image is build on Hydra. Note that this image is not using u-boot, but rather the Raspberry Pi specific bootloader configuration.

Minimal configuration

Using nixos-generate-config will not generate the required minimal configuration. Change the lines about booting the the following (from this PR comment) (and don't forget to set a user).

/etc/nixos/configuration.nix

{ pkgs, ... }:

{
  # Assuming this is installed on top of the disk image.
  fileSystems = {
    "/boot" = {
      device = "/dev/disk/by-label/NIXOS_BOOT";
      fsType = "vfat";
    };
    "/" = {
      device = "/dev/disk/by-label/NIXOS_SD";
      fsType = "ext4";
    };
  };
  boot.loader.grub.enable = false;
  boot.loader.raspberryPi.enable = true;
  boot.loader.raspberryPi.version = 4;
  # Mainline doesn't work yet
  boot.kernelPackages = pkgs.linuxPackages_rpi4;

  # ttyAMA0 is the serial console broken out to the GPIO
  boot.kernelParams = [
    "console=ttyAMA0,115200"
    "console=tty1"
  ];

  # Required for the Wireless firmware
  hardware.enableRedistributableFirmware = true;
}

USB boot

For USB booting to work properly, firmware update might be needed:

nix-shell -p raspberrypi-eeprom
rpi-eeprom-update -d -a

Now reboot the device so it can update the firmware from boot partition.

When running from USB device without SD card present, kernel spams log about missing SD card, workaround for this is to set:

boot.loader.raspberryPi.firmwareConfig = "dtparam=sd_poll_once=on";

GPU support

The following configuration samples are built on the assumption that they are added to an already working configuration. They are not complete configurations.

Without GPU

/etc/nixos/configuration.nix

{
  services.xserver = {
    enable = true;
    displayManager.slim.enable = true;
    desktopManager.gnome3.enable = true;
    videoDrivers = [ "fbdev" ];
  };
}

With GPU

/etc/nixos/configuration.nix

{ pkgs, ... }:

{
  hardware.opengl = {
    enable = true;
    setLdLibraryPath = true;
    package = pkgs.mesa_drivers;
  };
  hardware.deviceTree = {
    base = pkgs.device-tree_rpi;
    overlays = [ "${pkgs.device-tree_rpi.overlays}/vc4-fkms-v3d.dtbo" ];
  };
  services.xserver = {
    enable = true;
    displayManager.slim.enable = true;
    desktopManager.gnome3.enable = true;
    videoDrivers = [ "modesetting" ];
  };
  boot.loader.raspberryPi.firmwareConfig = ''
    gpu_mem=192
  '';
}

Tools

The raspberry tools are available in the raspberrypi-tools package and include commands like vcgencmd to measure temperature and CPU frequency.

Audio

In addition to the usual config, you will need to enable audio support explicitly in the firmwareConfig.

/etc/nixos/configuration.nix

  sound.enable = true;
  hardware.pulseaudio.enable = true;

  boot.loader.raspberryPi.firmwareConfig = ''
    dtparam=audio=on
  '';

Troubleshooting

Power issues

The Raspberry Pi 4B is as power-hungry, if not more, as its predecessors. It is important to have a sufficient enough power supply or weirdness may happen. Weirdness may include:

• Lightning bolt on HDMI output "breaking" the display.
• Screen switching back to u-boot text
  • Fixable temporarily when power is sufficient by switching VT (alt+F2 / alt+F1)
• Random hangs

Note: A properly rated USB power supply, AND a good cable are necessary. The cable has to be short enough to not incur power losses through the length. Do note that thin and cheap cables usually have thinner copper wires, which in turn accentuates power losses.

Note that the Type-C USB receptacle for the Raspberry Pi 4B does not implement Power Delivery (USB PD). This means that it is limited to whatever the power supply will provide when not negotiating power, which is most likely 5V at some undetermined power level.

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