u-boot-radxa-rock-4d

This repository provides a custom-built U-Boot firmware for the Radxa ROCK 4D (RK3576). Unlike the stock bootloader from the vendor, this version is specifically configured to initialize the onboard USB 3.0/2.0 controllers and the Naneng Combo PHY, enabling seamless and automatic booting from USB drives.

Background

1. Vendor Limitations: The official Radxa ROCK 4D bootloader does not support booting from USB disks; it is primarily designed for eMMC, SD, or NVMe storage via the board built-in FPC connector.
2. OS Limitations: Standard OS images (such as Raspbian or Debian ports for ROCK 4D) include a few different bootloader configs that lack the necessary drivers to initialize the USB controllers during the boot sequence.
3. Solution: A custom configuration of Mainlline U-Boot from source, specifically tailored for the ROCK 4D (RK3576), to include USB Host, xHCI, and Naneng Combo PHY support.

Build Process

The following steps were performed to generate the working firmware:

1. Source and binaries retrieval

# Clone Rockchip binary blobs (TPL/BL31)
git clone --depth 1 https://github.com/rockchip-linux/rkbin

# Clone Mainline U-Boot source code
git clone https://source.denx.de/u-boot/u-boot.git

2. Environment Configuration

cd u-boot
export BL31=../rkbin/bin/rk35/rk3576_bl31_v1.20.elf
export ROCKCHIP_TPL=../rkbin/bin/rk35/rk3576_ddr_lp4_2112MHz_lp5_2736MHz_v1.09.bin

# Apply the default U-Boot configuration for the ROCK 4D
make rock-4d-rk3576_defconfig

3. Key config modifications (make menuconfig)

The following options were enabled to ensure full USB support while keeping the SPL (Secondary Program Loader) size within limits and avoiding compilation errors:

• USB Host Support: CONFIG_USB=y, CONFIG_USB_HOST=y, CONFIG_DM_USB=y,
• Drivers: CONFIG_USB_XHCI_HCD=y, CONFIG_USB_XHCI_DWC3=y, CONFIG_USB_DWC3=y, CONFIG_USB_DWC3_GENERIC=y
• PHY Support: CONFIG_PHY_ROCKCHIP_NANENG_COMBPHY=y, CONFIG_PHY_ROCKCHIP_INNO_USB2=y
• Storage: CONFIG_USB_STORAGE=y
• Controller Limit: CONFIG_USB_HOST_MAX=2
• SPL Compatibility: CONFIG_SPL_USB_HOST=n (disabled to prevent SPL size overflow and linker errors)

Instead of manually configuring the build via make menuconfig, you can use the pre-configured config file in this repository:

1. Download the rock-4d-rk3576_u-boot_usb_defconfig file from this repo.
2. Rename the file as .config and place it into your u-boot source root directory.
3. Skip the make menuconfig step and proceed directly to compilation.

4. Native Compilation on ROCK 4D SBC board

The build produces the file u-boot-rockchip-spi.bin, which is ready to be flashed to the onboard SPI Flash.

# Pre-requisites
sudo apt-get install bc bison build-essential coccinelle \
  device-tree-compiler dfu-util efitools flex gdisk graphviz imagemagick \
  libgnutls28-dev libguestfs-tools libncurses-dev \
  libpython3-dev libsdl2-dev libssl-dev lz4 lzma lzma-alone openssl \
  pkg-config python3 python3-asteval python3-coverage python3-filelock \
  python3-pkg-resources python3-pycryptodome python3-pyelftools \
  python3-pytest python3-pytest-xdist python3-sphinxcontrib.apidoc \
  python3-sphinx-rtd-theme python3-subunit python3-testtools \
  python3-venv swig uuid-dev

# Build the u-boot firmware
make

Alternative: make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- for u-boot cross-compilation on a x86_64 PC.

5. Flash to SPI Flash

From a running Linux system on the ROCK 4D, identify the SPI device (usually /dev/mtdblock0) and run:

# Reset SPI flash (optional but recommended)
sudo dd if=/dev/zero of=/dev/mtdblock0 bs=1M count=4 2>/dev/null
# flash the SPI bootloader
sudo dd if=u-boot-rockchip-spi.bin of=/dev/mtdblock0 bs=4K
sync
# Verify written image (optional but recommended): the two commands below should give the same result 
sudo head -c $(stat -c%s u-boot-rockchip-spi.bin) /dev/mtdblock0 | md5sum
md5sum u-boot-rockchip-spi.bin

Expected Results

Using this custom U-Boot build, the ROCK 4D board should be capable of:

• Initializing the USB bus automatically at power-on.
• Detecting USB Mass Storage devices.
• Booting Linux distributions (like Armbian) stored on USB disks without any manual console commands.

Verified Test Environment

The custom U-Boot build has been successfully verified with the following configuration:

Operating System

• Linux Distribution: Armbian 26.2.0-trunk.363 (Ubuntu 24.04 LTS "noble")
• Kernel: Mainline-based Armbian build for ROCK 4D

Storage Hardware

• Device: SSK USB 3.2 SSD Flash Drive
• Controller: VIA Labs, Inc. VL817 SATA Adaptor (ID 2109:0715)
• Interface: USB 3.1 SuperSpeed (bcdUSB 3.10)

Obtained results

U-Boot initializes the USB 3.x controller, detects the VIA Labs bridge, and hands over the boot sequence to Armbian OS without any manual UART console intervention.

Boot Log (UART Debug)

Click to expand the full boot sequence log

DR 2f85f4b2d4 cym 24/11/07-19:07:28,fwver: v1.09
In
ch0 ttot6
ch1 ttot6
... [DDR Initialization] ...
U-Boot SPL 2026.04-rc1-00063-geed514b11d04 (Jan 31 2026 - 22:29:40 +0100)
Trying to boot from SPI
## Checking hash(es) for config config-1 ... OK
...
U-Boot 2026.04-rc1-00063-geed514b11d04 (Jan 31 2026 - 22:29:40 +0100)
Model: Radxa ROCK 4D
SoC:   RK3576
DRAM:  4 GiB
...
USB XHCI 1.10
USB XHCI 1.10
Bus usb@23000000: 2 USB Device(s) found
Bus usb@23400000: 3 USB Device(s) found
Scanning bootdev 'usb_mass_storage.lun0.bootdev':
  0  script       ready   usb_mass_    1  usb_mass_storage.lun0.boo /boot/boot.scr
** Booting bootflow 'usb_mass_storage.lun0.bootdev.part_1' with script
Boot script loaded from usb 0:1
...
Starting kernel ...
Armbian 26.2.0-trunk.363 noble ttyFIQ0 
radxa-rock-4d login:

Performance Benchmarks - Sequential Write Bandwidth and Latency

To quantify the benefits of enabling USB 3.2 boot support, a comparative I/O performance test was conducted using fio. The tests compare the SSK USB 3.2 SSD Flash Drive (connected via the reconfigured USB 3.0 port) against the sdcard storage SandDisk Ultra microSDXC UHS-I A1 (mmcblk1).

Storage Media	Write Bandwidth (BW)	IOPS	Avg. Latency (clat)
SSK USB 3.2 SSD (USB 3.0)	317 MB/s	2417	51.01 ms
SandDisk Ultra microSDXC UHS-I A1 sdcard	25.3 MB/s	192	660.92 ms

Conclusions

1. Speed: The USB 3.2 SSD is 12.5x faster than the A1-rated microSD card in sequential write operations.
2. IOPS: The USB setup handles over 2400 operations per second, compared to fewer than 200 on the sdcard media, making it a superior choice for running a database or a desktop environment.
3. Responsiveness: The average latency on the USB drive is 13x lower (51ms vs 660ms), which significantly improves system responsiveness, especially during heavy I/O tasks or software updates.

Enabling USB boot via this custom U-Boot build doesn't just provide a convenient storage alternative; it unlocks a massive performance tier for the ROCK 4D, transforming it from a standard SBC into a high-performance node capable of saturating the USB 3.0 bus.