4.23. RISC-V

4.23.1. QEMU Virt

barebox supports both the qemu riscv32 and riscv64 -M virt boards:

make ARCH=riscv rv64i_defconfig
qemu-system-riscv64 -M virt -serial stdio -kernel build/images/barebox-dt-2nd.img

For 32-bit builds use virt32_defconfig. VirtIO Support over MMIO is supported and can be used for e.g. an extra console or to pass in a virtio-blk device:

qemu-system-riscv64 -M virt -serial stdio                                \
      -kernel ./images/barebox-dt-2nd.img                                \
      -device virtio-rng-device                                          \
      -drive if=none,file=./images/barebox-dt-2nd.img,format=raw,id=hd0  \
      -device virtio-blk-device,drive=hd0                                \
      -device virtio-serial-device                                       \
      -chardev socket,path=/tmp/foo,server,nowait,id=foo                 \
      -device virtconsole,chardev=foo,name=console.foo

barebox 2021.02.0 #27 Sun Mar 14 10:08:09 CET 2021

Board: riscv-virtio,qemu
malloc space: 0x83dff820 -> 0x87bff03f (size 62 MiB)

barebox@riscv-virtio,qemu:/ filetype /dev/virtioblk0
/dev/virtioblk0: RISC-V Linux image (riscv-linux)

Note that the board-dt-2nd.img uses the Linux RISC-V kernel image format and boot protocol. It thus requires the device tree to be passed from outside in a1 and must be loaded at an offset as indicated in the header for the initial stack to work. Using the -kernel option in Qemu or booting from bootloaders that can properly boot Linux will take care of this.

4.23.2. TinyEMU

TinyEMU can emulate a qemu-virt like machine with a RISC-V 32-, 64- and 128-bit CPU. It can run 32-bit barebox with this sample configuration:

    version: 1,
    machine: "riscv32",
    memory_size: 256,
    bios: "bbl32.bin",
    kernel: "images/barebox-dt-2nd.img",

as well as 64-bit barebox with this configuration:

    version: 1,
    machine: "riscv64",
    memory_size: 256,
    bios: "bbl64.bin",
    kernel: "images/barebox-dt-2nd.img",

barebox-dt-2nd.img can be generated like with Qemu. Graphical output and input are also supported. To activate add:

display0: { device: "simplefb", width: 800, height: 600 },
input_device: "virtio",

into the config file.

See https://barebox.org/jsbarebox/?graphic=1 for a live example.

4.23.3. BeagleV

barebox has second-stage support for the BeagleV Starlight:

make ARCH=riscv rv64i_defconfig

Thie resulting ./images/barebox-beaglev-starlight.img can be used as payload to opensbi:

git clone https://github.com/starfive-tech/opensbi
cd opensbi
export ARCH=riscv
export PLATFORM=starfive/vic7100
export FW_PAYLOAD_PATH=$BAREBOX/build/images/barebox-beaglev-starlight.img

make ARCH=riscv
./fsz.sh ./build/platform/starfive/vic7100/firmware/fw_payload.bin fw_payload.bin.out
ls -l $OPENSBI/build/platform/starfive/vic7100/firmware/fw_payload.bin.out

The resulting ./platform/starfive/vic7100/firmware/fw_payload.bin.out can then be flashed via Xmodem to the board:

picocom -b 115200 /dev/ttyUSB0 --send-cmd "sx -vv" --receive-cmd "rx -vv"
0:update uboot
select the function: 0␤
send file by xmodem

After reset, barebox should then boot to shell and attempt booting kernel Image and device tree jh7100-starlight.dtb from the first root partition with the same partition as rootfs. Note that while barebox does take over some initialization, because of lack of Linux drivers, it doesn’t yet do everything. If you experience boot hangs, you may need to disable devices (or extend the starfive-pwrseq driver to initialize it for you).

4.23.4. Erizo Running on qemu

Obtain RISC-V GCC/Newlib Toolchain, see https://github.com/riscv/riscv-tools/blob/master/README.md for details. The build.sh script from riscv-tools should create toolchain.

Next compile qemu emulator:

$ git clone -b 20180409.erizo https://github.com/miet-riscv-workgroup/riscv-qemu
$ cd riscv-qemu
$ cap="no" ./configure \
  --extra-cflags="-Wno-maybe-uninitialized" \
  --audio-drv-list="" \
  --disable-attr \
  --disable-blobs \
  --disable-bluez \
  --disable-brlapi \
  --disable-curl \
  --disable-curses \
  --disable-docs \
  --disable-kvm \
  --disable-spice \
  --disable-sdl \
  --disable-vde \
  --disable-vnc-sasl \
  --disable-werror \
  --enable-trace-backend=simple \
  --disable-stack-protector \
$ make

Next compile barebox:

$ make erizo_generic_defconfig ARCH=riscv
$ make ARCH=riscv CROSS_COMPILE=<path to your riscv toolchain>/riscv32-unknown-elf-

Run barebox:

$ <path to riscv-qemu source>/riscv32-softmmu/qemu-system-riscv32 \
    -nographic -M erizo -bios ./images/barebox-erizo-generic.img \
    -serial stdio -monitor none -trace file=/dev/null
Switch to console [cs0]

barebox 2018.12.0-00148-g60e49c4e16 #1 Tue Dec 18 01:12:29 MSK 2018

Board: generic Erizo SoC board
malloc space: 0x80100000 -> 0x801fffff (size 1 MiB)
running /env/bin/init...
/env/bin/init not found
barebox:/ Running on DE0-Nano FPGA board

See https://github.com/open-design/riscv-soc-cores/ for instructions on DE0-Nano bitstream generation and loading.

Connect to board’s UART with your favorite serial communication software (e.g. minicom) and check ‘nmon> ‘ prompt (nmon runs from onchip ROM).

Next close your communication software and use ./scripts/nmon-loader to load barebox image into board’s DRAM, e.g.:

# ./scripts/nmon-loader barebox.erizo.nmon /dev/ttyUSB0 115200

Wait several munutes for ‘nmon> ‘ prompt.

Next, start barebox from DRAM:

nmon> g 80000000
Switch to console [cs0]

barebox 2018.12.0-00148-g60e49c4e16 #1 Tue Dec 18 01:12:29 MSK 2018

Board: generic Erizo SoC board
malloc space: 0x80100000 -> 0x801fffff (size 1 MiB)
running /env/bin/init...
/env/bin/init not found

4.23.5. Allwinner D1 Nezha

Barebox has limited second-stage support for the Allwinner D1 Nezha (sun20i):

ARCH=riscv make rv64i_defconfig
ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make

The resulting ./images/barebox-allwinner-d1.img can be used as 2nd stage image which gets called by opensbi:

git clone https://github.com/tekkamanninja/opensbi -b allwinner_d1
cd opensbi
CROSS_COMPILE=riscv64-linux-gnu- PLATFORM=generic FW_PIC=y make

The resulting ./build/platform/generic/firmware/fw_dynamic.bin is loaded by the 1st stage (spl) loader, which is basically a u-boot spl:

git clone https://github.com/smaeul/sun20i_d1_spl -b mainline
cd sun20i_d1_spl
CROSS_COMPILE=riscv64-linux-gnu- make p=sun20iw1p1 mmc

The resulting ./nboot/boot0_sdcard_sun20iw1p1.bin image used as 1st stage bootloader which loads all necessary binaries: dtb, opensbi and barebox to the dedicated places in DRAM. After loading it jumps to the opensbi image. The initial dtb can be taken from u-boot:

git clone https://github.com/smaeul/u-boot.git -b d1-wip
cd u-boot
ARCH=riscv make nezha_defconfig
ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- make

Make will print two warnings at the end of this command but those can be ignored since we only want the devicetree blob which can be found under ./u-boot.dtb.

The final image is build by mkimage. It is some sort of a self-defined toc1 format. So we need to compile the mkimage with the toc1 format support as first:

cd u-boot
make tools-only

The resulting tools/mkimage is used to build the toc1 image which is loaded by the 1st stage bootloader from the mmc interface. To build the final toc1 image we need to specify a toc1.cfg like:

file = <ABSOLUT_PATH_TO>/opensbi/build/platform/generic/firmware/fw_dynamic.bin
addr = 0x40000000
file = <ABSOLUT_PATH_TO>/u-boot/u-boot.dtb
addr = 0x44000000
file = <ABSOLUT_PATH_TO>/barebox/images/barebox-allwinner-d1.img
addr = 0x4a000000

Then we need to call:

mkimage -T sunxi_toc1 -d toc1.cfg boot.toc1

The last part is to place the 1st stage bootloader and the boot.toc1 image onto the correct places. So the ROM loader can find the 1st stage bootloader and the 1st bootloader can find the boot.toc1 image. This is done by:

dd if=boot0_sdcard_sun20iw1p1.bin of=/dev/sd<X> bs=512 seek=16
dd if=boot.toc1 of=/dev/sd<X> bs=512 seek=32800

Now plug in the sdcard and power device and you will see:

[309]HELLO! BOOT0 is starting!
[312]BOOT0 commit : 882671f-dirty
[315]set pll start
[317]periph0 has been enabled
[320]set pll end
[322]board init ok


OpenSBI v0.9-204-gc9024b5
   ____                    _____ ____ _____
  / __ \                  / ____|  _ \_   _|
 | |  | |_ __   ___ _ __ | (___ | |_) || |
 | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
 | |__| | |_) |  __/ | | |____) | |_) || |_
  \____/| .__/ \___|_| |_|_____/|____/_____|
        | |

Platform Name             : Allwinner D1 Nezha
Platform Features         : medeleg


barebox 2022.08.0-00262-g38678340903b #1 Tue Sep 13 12:54:29 CEST 2022

Board: Allwinner D1 Nezha


barebox@Allwinner D1 Nezha:/