4.22. RISC-V

4.22.1. QEMU Virt

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

make ARCH=riscv virt64_defconfig
qemu-system-riscv64 -M virt -serial stdio -kernel build/images/barebox-dt-2nd.img

Replace 64 by 32 for 32-bit build. 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.

4.22.2. TinyEMU

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

/* temu barebox-virt64.cfg */
{
    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 is also supported, but virtio input support is still missing. To activate add:

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

into the config file.

4.22.3. Erizo

4.22.3.1. 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 \
  --target-list=riscv32-softmmu,riscv64-softmmu
$ 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:/

4.22.4. 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 barebox:/