Linux + Buildroot

This page builds a SPI NOR boot image for the F101-S3 with YuzukiNeko’s Buildroot external tree, producing the complete 16 MiB image with a single make. The boot chain is:

BROM → SyterKit → OpenSBI → Linux → BusyBox

There are two defconfigs, by CPU mode: RV32 and RV64I. The root filesystem is SquashFS, with a writable JFFS2 overlay on top. For how to flash the built image, how to connect the serial port, and how to replace a single component, see Prebuilt images; for a step-by-step manual build, see Manual build.

Building from source

Both images are produced by the external tree YuzukiHD/buildroot-external-yuzukihd. Buildroot itself uses the official mainline buildroot/buildroot repository; the board defconfigs, SyterKit build rules, and post-processing scripts are all in the external tree.

defconfig	Architecture	Bootloader
`yuzukihd_yuzukineko_nor_defconfig`	RV32 (C907 / ilp32)	`spinor-boot_spi.bin`
`yuzukihd_yuzukineko_rv64i_nor_defconfig`	RV64I (lp64)	`spinor-boot-rv64i_spi.bin`

Each defconfig selects SyterKit (YuzukiHD/SyterKit), OpenSBI fw_jump (YuzukiHD/opensbi, branch sun252i-f101), the Linux Image and devicetree (YuzukiHD/linux-mainline, branch sun252i_f101_7.2), and a SquashFS (xz) root filesystem. A post-processing script then assembles the 16 MiB images/yuzukineko-nor.img.

Build outside the source tree, with output in build/. First clone the two repositories into your working directory:

mkdir -p ~/f101-linux/build && cd ~/f101-linux
git clone https://github.com/buildroot/buildroot.git
git clone https://github.com/YuzukiHD/buildroot-external-yuzukihd.git

RV32:

cd buildroot
make O=../build/br-rv32 BR2_EXTERNAL=../buildroot-external-yuzukihd yuzukihd_yuzukineko_nor_defconfig
make O=../build/br-rv32 BR2_EXTERNAL=../buildroot-external-yuzukihd -j8

Output at the end of the build (the LIMIT column is the reserved size of each region):

== build/br-rv32/images/yuzukineko-nor.img : 16 MiB SPI NOR image (RV32 (C907 / ilp32)) ==
  REGION      OFFSET          SIZE  LIMIT    CONTENT
  bootloader  0x000000      48 KiB  <64K     spinor-boot_spi.bin
  dtb         0x010000      11 KiB  <256K    sun252i-f101-yuzukineko.dtb
  fw_jump     0x050000     261 KiB  <512K    fw_jump.bin
  Image       0x0d0000    5121 KiB  <6M      Image
  rootfs      0x6d0000    1252 KiB  <8.2M    rootfs.squashfs
  overlay     0xf00000    1024 KiB  =1M      erased; JFFS2 overlayfs upper
== done: build/br-rv32/images/yuzukineko-nor.img (16384 KiB on disk) ==

RV64I:

make O=../build/br-rv64i BR2_EXTERNAL=../buildroot-external-yuzukihd yuzukihd_yuzukineko_rv64i_nor_defconfig
make O=../build/br-rv64i BR2_EXTERNAL=../buildroot-external-yuzukihd -j8

Output at the end of the build:

== build/br-rv64i/images/yuzukineko-nor.img : 16 MiB SPI NOR image (RV64I (lp64)) ==
  REGION      OFFSET          SIZE  LIMIT    CONTENT
  bootloader  0x000000      48 KiB  <64K     spinor-boot-rv64i_spi.bin
  dtb         0x010000      11 KiB  <256K    sun252i-f101-yuzukineko-rv64i.dtb
  fw_jump     0x050000     263 KiB  <512K    fw_jump.bin
  Image       0x0d0000    5744 KiB  <6M      Image
  rootfs      0x6d0000    1224 KiB  <8.2M    rootfs.squashfs
  overlay     0xf00000    1024 KiB  =1M      erased; JFFS2 overlayfs upper
== done: build/br-rv64i/images/yuzukineko-nor.img (16384 KiB on disk) ==

The first build has to download the source of each component and compile Buildroot’s bundled musl toolchain, so it takes a while. When it finishes, the images are at build/br-rv32/images/yuzukineko-nor.img and build/br-rv64i/images/yuzukineko-nor.img, both 16,777,216 bytes. The same directory also holds the individual components, which can be used directly to replace a single component:

File	RV32 size (bytes)	RV64I size (bytes)
`spinor-boot_spi.bin` / `spinor-boot-rv64i_spi.bin`	49,152	49,152
`sun252i-f101-yuzukineko.dtb` / `…-rv64i.dtb`	10,284	10,284
`fw_jump.bin`	266,352	268,744
`Image`	5,243,808	5,881,208
`rootfs.squashfs`	1,282,048	1,253,376

The table above comes from one build with Buildroot 2026.08-323-g45f1c387e0 (external tree 1e250e5). For the flashing method, see Prebuilt images.

Both defconfigs build SyterKit with the x86_64 Xuantie-900 ELF/Newlib V3.2.0 toolchain, because SyterKit’s C907-specific compile options require it; the root filesystem uses Buildroot’s bundled musl toolchain. The *_xuantie_nor_defconfig variants also switch the root filesystem to the Xuantie musl32 toolchain.

The images in this repository were built with the Buildroot version recorded in manifest.json. The external tree and the kernel and OpenSBI branches keep changing, so a rebuild is unlikely to produce byte-identical files.