Running Linux on LiteX-based RISC-V SoC

Dependencies on Ubuntu 18.04

Install dependencies with

sudo apt install device-tree-compiler bison flex

You will also need to run this to add a symlink for this library:

sudo ln -s /usr/lib/x86_64-linux-gnu/libmpfr.so.6 /usr/lib/x86_64-linux-gnu/libmpfr.so.4

Edit your ~/.bashrc file and add these two lines to the end. Make sure to replace with your actual path:

export PATH=$PATH:/path/to/riscv-gnu-toolchain/bin
export PATH=$PATH:/path/to/riscv-gcc/bin

Close and re-open your bash window to load these new variables.

Getting the toolchain

wget www.antmicro.com/downloads/riscv-gnu-toolchain.tar.gz

Getting the sources

git clone https://github.com/antmicro/litex-linux-riscv.git

Building

kernel configuration:

cd litex-linux-riscv
cp litex_default_configuration .config
ARCH=riscv CROSS_COMPILE=riscv32-unknown-linux-gnu- make -j`nproc`
riscv32-unknown-linux-gnu-objcopy -O binary vmlinux vmlinux.bin

devicetree:

dtc -I dts -O dtb -o vmlinux.dtb rv32.dts

Litex SoC

Litex requires different gcc toolchain than Linux. The toolchain can be obtained with:

wget www.antmicro.com/downloads/riscv-gcc.tar.gz

Getting the sources

git clone https://github.com/antmicro/litex-rv32-linux-system
cd litex-rv32-linux-system
git submodule update --init --recursive

Building the SoC

source env.sh
# to generate verilog run
make verilog
# to generate verilog, build the system and generate programming file run (this step requires microsemi tools intalled)
make

U-Boot

U-Boot sources can be obtained with:

git clone https://github.com/antmicro/RV32_U-Boot
cd RV32_U-Boot
git checkout 32bit

Building

make rv32_defconfig
make -j`nproc`

openOCD

Getting the sources:

git clone https://github.com/SpinalHDL/openocd_riscv

building

./configure --enable-ftdi --enable-dummy --disable-werror
make -j`nproc`
sudo make install

connecting to the board

openocd -f vexriscv.cfg

in a separate terminal run telnet and connect to the openOCD

telnet localhost 4444

upload and run Linux:

halt
load_image /path/to/vmlinux.bin 0x40000000
load_image /path/to/vmlinux.dtb 0x41000000
load_image /path/to/initramdisk.gz 0x42000000
resume 0xC0000000

Renode

To run Renode go to http://github.com/renode/renode and get the vexriscv branch.

After you compile it, open the scripts/hackaton file and adjust the paths to the vmlinux, dtb and rootfs files.

Then start Renode and run:

s @scripts/hackaton

Ideas

• run the LiteX SoC in Verilator and describe what you needed to do, try to run the Linux there
• add storage drivers in U-Boot for the SPI Flash
• same but for Linux
• route LiteEth (a LiteX IP) to the Ethernet on the board and implement support for it in the LiteX BIOS
• same but for U-Boot
• same but for Linux
• run Zephyr on the LiteX SoC (our Zephyr port is https://github.com/antmicro/zephyr/tree/litex-vexriscv, should be straightforward)
• add support for the weather and luminosity shields as Zephyr drivers
• add functional models for LiteEth, LiteI2C or LiteSPI for Renode
• add your own via a pull request!