{ config, lib, pkgs, modulesPath, ... }:

let
  overlay = final: prev: {
    uboot = prev.ubootQemuRiscv64Smode.override {
      filesToInstall = [ "u-boot.bin" "u-boot-nodtb.bin" ];
      extraConfig = ''
        CONFIG_RISCV=y
        CONFIG_RISCV_SMODE=y
        CONFIG_SYS_MALLOC_LEN=0x800000
        CONFIG_NR_DRAM_BANKS=1
        CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
        CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x80200000
        CONFIG_ENV_SIZE=0x20000
        CONFIG_SYS_LOAD_ADDR=0x80200000
        CONFIG_ARCH_RV64I=y
        CONFIG_FIT=y
        CONFIG_DISTRO_DEFAULTS=y
        CONFIG_DISPLAY_CPUINFO=y
        CONFIG_DISPLAY_BOARDINFO=y
        CONFIG_SYS_CBSIZE=256
        CONFIG_SYS_PBSIZE=276
        CONFIG_SYS_BOOTM_LEN=0x4000000
        CONFIG_CMD_BOOTEFI_SELFTEST=y
        CONFIG_CMD_NVEDIT_EFI=y
        # CONFIG_CMD_MII is not set
        CONFIG_SYS_RELOC_GD_ENV_ADDR=y
        CONFIG_DM_MTD=y
        CONFIG_FLASH_SHOW_PROGRESS=0
        CONFIG_SYS_MAX_FLASH_BANKS=2
        #CONFIG_TEXT_BASE=0x80000000
        # -------------------------
        CONFIG_RISCV_ISA_C=n
        # CONFIG_OF_EMBED=n
        # CONFIG_OF_SEPARATE=y
        # CONFIG_OF_OMIT_DTB=y
        CONFIG_REQUIRE_SERIAL_CONSOLE=n
        CONFIG_SERIAL_SEARCH_ALL=y
        CONFIG_OF_CONTROL=y
        CONFIG_OF_BOARD=y
        CONFIG_OF_HAS_PRIOR_STAGE=y
        CONFIG_BLKMAP=y
        CONFIG_CMD_BLKMAP=y
        CONFIG_SBI_V01=y
        CONFIG_DEBUG_UART=y
        CONFIG_DEBUG_UART_ANNOUNCE=y
        CONFIG_DEBUG_SBI_CONSOLE=y
      '';
    };

    opensbi = prev.opensbi.overrideAttrs (old: {
      makeFlags = old.makeFlags ++ [
          # Build OpenSBI without compressed instructions
          "PLATFORM_RISCV_ISA=rv64g"
          "PLATFORM=fpga/openpiton"
          # Check with: riscv64-unknown-elf-objdump -d -M no-aliases rotate
          "FW_PAYLOAD_PATH=${final.uboot-fpga}/u-boot-nodtb.bin"
      ];
    });
  };
in {
  nixpkgs.overlays = [ overlay ];

  #boot.kernelPackages = pkgs.linuxPackages_latest;
  boot.kernelPatches = [
    {
      name = assert false; "sbi-early-console";
      patch = null;
      extraConfig = ''
        # Early console via SBI
        RISCV_SBI y
        RISCV_SBI_V01 y
        SERIAL_EARLYCON y
        SERIAL_EARLYCON_RISCV_SBI y
        HVC_DRIVER y
        HVC_RISCV_SBI y
      '';
    }
  ];
}