f54c3bcb65
Adds hardware.raspberry-pi.firmware to stage the Pi's pre-Linux boot files (GPU boot code, DTBs, overlays, config.txt, optionally U-Boot) onto the firmware partition. Boards still boot via generic-extlinux-compatible; this only supplies the files it needs, through populateCmd for image builders or an opt-in activation script. DTB/overlay copy adapted from nvmd/nixos-raspberrypi.
77 lines
4.2 KiB
Markdown
77 lines
4.2 KiB
Markdown
# Raspberry Pi
|
|
|
|
NixOS profiles and modules for Raspberry Pi boards.
|
|
|
|
## What's here
|
|
|
|
- `common/` has the shared bits: the `linux-rpi` kernel build (vendor defconfig, matching firmware), the `config.txt` generation module, a pinned wireless firmware, and the firmware-partition install module.
|
|
- `2/`, `3/`, `4/`, `5/` are the board profiles. Each one picks the right kernel and kernel params. Pi 4 and 5 also set DT filters and the initrd modules they need.
|
|
- The extra files under `4/` are opt-in toggles for Pi 4 hardware: audio, dwc2, GPIO, I2C, LEDs, the PoE HATs, touchscreens, and so on.
|
|
|
|
## Using a board profile
|
|
|
|
```nix
|
|
{
|
|
imports = [
|
|
<nixos-hardware/raspberry-pi/4>
|
|
];
|
|
}
|
|
```
|
|
|
|
These profiles assume the `generic-extlinux-compatible` bootloader (the NixOS module that writes an `extlinux.conf` for U-Boot to read), which is what aarch64 NixOS SD images use by default. There is no `boot.loader.raspberry-pi` module here. U-Boot and the GPU boot code still have to land on the firmware partition somehow: either your image builder does it, or you use the firmware install module below.
|
|
|
|
## Firmware install
|
|
|
|
`hardware.raspberry-pi.firmware` stages the files the Pi firmware needs before Linux starts onto the firmware partition (default `/boot/firmware`): GPU boot code (`bootcode.bin`, `start*.elf`, `fixup*.dat`), vendor device trees and overlays, the rendered `config.txt`, and optionally U-Boot. It is not a new boot method; it just supplies the files the existing `generic-extlinux-compatible` + U-Boot path needs.
|
|
|
|
When you build an SD image, the module sets `sdImage.populateFirmwareCommands` itself, so the firmware partition is populated at build time with no extra configuration.
|
|
|
|
For a running system, set `hardware.raspberry-pi.firmware.enable = true`. An activation script then repopulates the firmware partition on every `nixos-rebuild switch`. It is off by default.
|
|
|
|
To chainload U-Boot from the firmware, enable `uboot.enable`. It copies `u-boot.bin` to the firmware partition and sets `config.txt`'s `kernel` line for you:
|
|
|
|
```nix
|
|
{
|
|
hardware.raspberry-pi.firmware = {
|
|
enable = true;
|
|
uboot.enable = true;
|
|
};
|
|
}
|
|
```
|
|
|
|
`uboot.enable` defaults `uboot.package` to nixpkgs' `pkgs.ubootRaspberryPiAarch64`, built from the upstream `rpi_arm64_defconfig`, which covers every 64-bit board (Pi 3/4/5). For a 32-bit board, override `uboot.package` with the matching U-Boot build. On the Pi 5 this boots from SD, but U-Boot can't drive USB/PCIe/RP1 yet, so USB boot, NVMe boot, and a USB keyboard at the U-Boot prompt don't work until Linux takes over.
|
|
|
|
## `config.txt`
|
|
|
|
Board profiles import `hardware.raspberry-pi.configtxt`, which renders `config.txt` from Nix options. The defaults track the Raspberry Pi OS pi-gen image: camera and display autodetect, KMS, audio on, `arm_boost`.
|
|
|
|
```nix
|
|
{
|
|
hardware.raspberry-pi.configtxt.settings = {
|
|
all = {
|
|
dtparam = [ "audio=on" ];
|
|
dtoverlay = [
|
|
"vc4-kms-v3d"
|
|
"disable-bt"
|
|
];
|
|
};
|
|
pi5.arm_freq = 2400;
|
|
cm4.otg_mode = true;
|
|
};
|
|
}
|
|
```
|
|
|
|
List values become repeated keys in the rendered file, so the `dtoverlay` above expands to:
|
|
|
|
```
|
|
dtoverlay=vc4-kms-v3d
|
|
dtoverlay=disable-bt
|
|
```
|
|
|
|
Top-level attrs are conditional sections (`all`, `pi4`, `pi5`, `cm4`, and so on). Nesting stacks filters. To drop a default, set the key to `null` with `mkForce`.
|
|
|
|
## Current limits
|
|
|
|
- No bootloader module: There's no `boot.loader.raspberry-pi` here. Boards rely on `generic-extlinux-compatible` plus U-Boot. Raspberry Pi OS has the GPU firmware load the kernel directly; we go through U-Boot so it reads `extlinux.conf`, which is what gives you the NixOS boot-generation menu and rollbacks. The firmware install module just stages the boot code and (optionally) U-Boot; it doesn't add a firmware-level direct-boot path. Pi 5 boots from SD via U-Boot, but USB, PCIe, and the RP1 don't come up until Linux takes over, so a USB keyboard at the U-Boot prompt won't work on Pi 5 today.
|
|
- Single pinned kernel: `common/kernel.nix` pins one `linux-rpi` version rather than matching each kernel to its firmware release.
|
|
- No Pi 0/02/1 board profiles: `common/kernel.nix` accepts `rpiVersion = 1`, but there's no `0/`, `02/`, or `1/` directory wiring that kernel up into a profile you can import via `<nixos-hardware/raspberry-pi/...>`.
|