Buildroot for MilkV Duo board

This Buildroot is for the MilkV Duo board and uses the standard gcc cross-compiler without using the RISC-V RVV extensions.

Getting the sources

$ git clone https://github.com/kinsamanka/milkv-buildroot.git

Alternatively :

$ curl -L https://github.com/kinsamanka/milkv-buildroot/archive/refs/heads/main.tar.gz | \
       tar xvzf -
$ mv milkv-buildroot-main milkv-buildroot

Prerequisites

On Ubuntu, the following command will install the needed packages:

$ sudo apt-get install bc bison build-essential flex libssl-dev unzip

For Fedora/CentOS/RHEL OS:

$ sudo yum install -y autoconf automake bc bison bzip2 cpio file flex gcc gcc-c++ openssl-devel \
                      ncurses-devel patchutils perl-core rsync tar unzip wget which

Build

This step will build the cross-compiler and then build the sd card image.

$ make O=$(pwd)/build -C milkv-buildroot milkv_duo_defconfig
$ cd build
$ make

If the build is successful, the images folder will contain the following files:

milkv-duo_sdcard.img.gz
milkv-duo_sdcard.img

Building the cross-compiler

To save time when creating future builds, it is best to create and re-use the cross-compiler. The following command will create the compiler.

$ make O=$(pwd)/sdk -C milkv-buildroot milkv_duo_toolchain_defconfig
$ cd sdk
$ make sdk

The resulting packaged cross-compiler: images/riscv64-buildroot-linux-musl_sdk-buildroot.tar.gz

Transfer this file to the root of the Buildroot directory:

$ mv images/riscv64-buildroot-linux-musl_sdk-buildroot.tar.gz ../milkv-buildroot

Using the packaged cross-compiler

Edit the buildroot .config file, change the following entries:

-BR2_TOOLCHAIN_BUILDROOT_MUSL=y
-BR2_KERNEL_HEADERS_5_10=y
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
+BR2_TOOLCHAIN_EXTERNAL_URL="file://$(TOPDIR)/riscv64-buildroot-linux-musl_sdk-buildroot.tar.gz"
+BR2_TOOLCHAIN_EXTERNAL_GCC_12=y
+BR2_TOOLCHAIN_EXTERNAL_HEADERS_5_10=y
+BR2_TOOLCHAIN_EXTERNAL_CUSTOM_MUSL=y

Notes

The behavior of the MilkV Duo board is set by the /etc/milkv-duo.conf file.

To disable the blinking LED, set ENABLE_BLINK to 0
To use the usb port as host, set USB_MODE to host