uboot nix derivation for Rock64 with CONFIG_BAUDRATE=115200

ubootRock64.nix

{ lib, buildUBoot, fetchFromGitHub, armTrustedFirmwareRK3328 }:
let
  rkbin = fetchFromGitHub {
    owner = "ayufan-rock64";
    repo = "rkbin";
    rev = "f79a708978232a2b6b06c2e4173c5314559e0d3a";
    sha256 = "0h7xm4ck3p3380c6bqm5ixrkxwcx6z5vysqdwvfa7gcqx5d6x5zz";
  };
in buildUBoot {
  extraMakeFlags = [ "all" "u-boot.itb" ];
  defconfig = "rock64-rk3328_defconfig";
  extraMeta = {
    platforms = [ "aarch64-linux" ];
    license = lib.licenses.unfreeRedistributableFirmware;
  };
  BL31="${armTrustedFirmwareRK3328}/bl31.elf";
  filesToInstall = [ "u-boot.itb" "idbloader.img"];
  # Derive MAC address from cpuid
  # Submitted upstream: https://patchwork.ozlabs.org/patch/1203686/
  extraConfig = ''
    CONFIG_MISC_INIT_R=y
    CONFIG_BAUDRATE=115200
  '';
  # Close to being blob free, but the U-Boot TPL causes random memory
  # corruption
  postBuild = ''
    ./tools/mkimage -n rk3328 -T rksd -d ${rkbin}/rk33/rk3328_ddr_786MHz_v1.13.bin idbloader.img
    cat spl/u-boot-spl.bin >> idbloader.img
  '';
}

Successfully cross-builds at 437e1f69be786bfbd06a611530bbd2fac6af1d35 nixpkgs commit:

$ nix-build -I nixpkgs=https://github.com/NixOS/nixpkgs/tarball/437e1f69be786bfbd06a611530bbd2fac6af1d35 -E 'with import <nixpkgs> {}; pkgsCross.aarch64
-multiplatform.callPackage ./ubootRock64.nix {}'