NixOS on RISC-V

This repo contains board-specific packages to get NixOS running on RISC-V platforms. I'm using this Nixpkgs tree.

Is it booting?

Yes! More details here.

Binary cache

Note The new binary cache is still being populated and most packages may not be available.

A binary cache is available with packages in binary-cache/world.nix. Use the following configurations:

substituters = https://cache.nixos.org https://beam.attic.rs/riscv
trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= riscv:TZX1ReuoIGt7QiSQups+92ym8nKJUSV0O2NkS4HAqH8=

Nixpkgs overlay

This repo provides a nixpkgs overlay at pkgs. This overlay does not override any existing packages, but provides new packages under the riscv64 hierarchy.

HiFive Unmatched

Installing U-Boot to the SPI Flash

It's recommended to install U-Boot to the on-board SPI flash using the installer image. You can obtain a pre-built installer image (unmatched-spi-installer.img) here, or build riscv64.uboot-unmatched-spi-installer. Burn the image into an SD card and insert it into the HiFive Unmatched. Ensure that the MSEL DIP switch has the factory default setting (MSEL[3:0] = 1011) to load U-Boot from the SD card.

MSEL Factory Defaults (MSEL[3:0] = 1011)

(Edge Of Board)

--------------- ON
|  | o | o o  |
|  o | o | |  |
--------------- OFF

BOOT MODE SEL

If successful, you should see the following in the serial console:

mmc0 is current device
Scanning mmc 0:3...
Found U-Boot script /boot.scr
2329 bytes read in 4 ms (568.4 KiB/s)
## Executing script at 88100000


Firmware installer


Installing U-Boot to the SPI flash in 10 seconds!
devtype = mmc
devnum = 0
bootpart = 3

:: Starting flash operation

-> Initializing SPI Flash subsystem...
SF: Detected is25wp256 with page size 256 Bytes, erase size 4 KiB, total 32 MiB

-> Reading new firmware from storage...
6291456 bytes read in 5419 ms (1.1 MiB/s)

-> Writing new firmware to SPI...
device 0 offset 0x0, size 0x600000
12288 bytes written, 6279168 bytes skipped in 15.45s, speed 449389 B/s

✅ Flashing seems to have been successful!
You can now set MSEL[3:0] = 0110

Resetting in 5 seconds
resetting ...
System reset not supported on this platform
### ERROR ### Please RESET the board ###

Now, configure the MSEL DIP switch like the following (MSEL[3:0]=0110):

(Edge Of Board)

--------------- ON
|  | | o o |  |
|  o o | | o  |
--------------- OFF

BOOT MODE SEL

If all goes well, you should be able to get into U-Boot without an SD card after powering your board back on.

Alternative: Manual installation from another Linux distro

Build pkgs.riscv64.uboot-unmatched-spi-image. Then, flash it onto the on-board SPI flash with:

modprobe mtdblock
dd if=spi-image.img of=/dev/mtdblock0 bs=4096 conv=sync

Alternative: Installing U-Boot onto the SD card

Note: With this method, you have to set up NixOS manually and can't use the pre-built SD image.

Build pkgs.riscv64.uboot-unmatched.

You need to create two GPT partitions on the SD card with the following sizes and GUIDs:

• 1MiB 5b193300-fc78-40cd-8002-e86c45580b47 (HiFive Unleashed FSBL)
• 4MiB 2e54b353-1271-4842-806f-e436d6af6985 (HiFive Unleashed BBL)

The easiest way to do this is with this command (you need pkgs.gptfdisk):

sgdisk -g --clear --set-alignment=1 \
    --new=1:34:+1M: --typecode=1:5b193300-fc78-40cd-8002-e86c45580b47 \
    --new=2:2082:+4M: --typecode=2:2e54b353-1271-4842-806f-e436d6af6985 \
    [block device]

Write the bootloader to the SD card as follows:

# FSBL
dd if=result/u-boot-spl.bin of=/dev/mmcblk0p1 bs=4k oflag=direct

# SBL
dd if=result/u-boot.itb of=/dev/mmcblk0p2 bs=4k oflag=direct

Configure MSEL like the following (MSEL[3:0]=1011, default configuration):

(Edge Of Board)

--------------- ON
|  | o | o o  |
|  o | o | |  |
--------------- OFF

BOOT MODE SEL

Installing NixOS onto the SD Card

Note: To use the pre-built SD image, you must have installed U-Boot onto the on-board SPI flash.

You can obtain a pre-built SD image (nixos-sd-image-unmatched.zst) here, or build riscv64.sd-image-unmatched. Decompress the image, then burn it into an SD card.

The image has the binary cache preconfigured, and you can reconfigure the SD image by running sudo nixos-rebuild switch. Alternatively, you can also install NixOS manually onto the NVMe drive using the SD image. If you choose to go the manual route, include nixos/unmatched.nix from this repo in your configuration.

StarFive VisionFive

You can obtain a pre-built SD image (nixos-sd-image-visionfive.zst) here, or build riscv64.sd-image-visionfive. Decompress the image, then burn it into an SD card.

The image has the binary cache preconfigured, and you can reconfigure the SD image by running sudo nixos-rebuild switch. Include nixos/visionfive.nix from this repo in your configuration.

References

• https://github.com/carlosedp/riscv-bringup/tree/master/unmatched
• NixOS/nixpkgs#115406

See Also

There are other efforts to bring NixOS to RISC-V:

• https://github.com/NickCao/nixos-riscv
• https://github.com/ius/jh7100