Milk-V Mars

U-Boot for the Milk-V Mars uses the same U-Boot binaries as the VisionFive 2 board. In U-Boot SPL the actual board is detected and the device-tree patched accordingly.

Building

  1. Add the RISC-V toolchain to your PATH.

  2. Setup ARCH & cross compilation environment variable:

export CROSS_COMPILE=<riscv64 toolchain prefix>

The M-mode software OpenSBI provides the supervisor binary interface (SBI) and is responsible for the switch to S-Mode. It is a prerequisite to build U-Boot. Support for the JH7110 was introduced in OpenSBI 1.2. It is recommended to use a current release.

git clone https://github.com/riscv/opensbi.git
cd opensbi
make PLATFORM=generic FW_TEXT_START=0x40000000 FW_OPTIONS=0

Now build the U-Boot SPL and U-Boot proper.

cd <U-Boot-dir>
make starfive_visionfive2_defconfig
make OPENSBI=$(opensbi_dir)/build/platform/generic/firmware/fw_dynamic.bin

This will generate the U-Boot SPL image (spl/u-boot-spl.bin.normal.out) as well as the FIT image (u-boot.itb) with OpenSBI and U-Boot.

Device-tree selection

Depending on the board version U-Boot set variable $fdtfile to either starfive/jh7110-starfive-visionfive-2-v1.2a.dtb or starfive/jh7110-starfive-visionfive-2-v1.3b.dtb.

To overrule this selection the variable can be set manually and saved in the environment

setenv fdtfile my_device-tree.dtb
env save

or the configuration variable CONFIG_DEFAULT_FDT_FILE can be used to set to provide a default value.

Preparing the SD-Card

The device firmware loads U-Boot SPL (u-boot-spl.bin.normal.out) from the partition with type GUID 2E54B353-1271-4842-806F-E436D6AF6985. You are free to choose any partition number.

With the default configuration U-Boot SPL loads the U-Boot FIT image (u-boot.itb) from partition 2 (CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION=0x2). When formatting it is recommended to use GUID BC13C2FF-59E6-4262-A352-B275FD6F7172 for this partition.

The FIT image (u-boot.itb) is a combination of OpenSBI’s fw_dynamic.bin, u-boot-nodtb.bin and the device tree blob.

Format the SD card (make sure the disk has GPT, otherwise use gdisk to switch)

sudo sgdisk --clear \
  --set-alignment=2 \
  --new=1:4096:8191 --change-name=1:spl --typecode=1:2E54B353-1271-4842-806F-E436D6AF6985\
  --new=2:8192:16383 --change-name=2:uboot --typecode=2:BC13C2FF-59E6-4262-A352-B275FD6F7172  \
  --new=3:16384:1654784 --change-name=3:system --typecode=3:EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 \
  /dev/sdb

Copy U-Boot to the SD card

sudo dd if=u-boot-spl.bin.normal.out of=/dev/sdb1
sudo dd if=u-boot.itb of=/dev/sdb2

sudo mount /dev/sdb3 /mnt/
sudo cp u-boot-spl.bin.normal.out /mnt/
sudo cp u-boot.itb /mnt/
sudo cp Image.gz /mnt/
sudo cp initramfs.cpio.gz /mnt/
sudo cp jh7110-starfive-visionfive-2.dtb /mnt/
sudo umount /mnt

Boot source selection

The board provides DIP switches to select the device for loading the boot firmware.

Boot source

SW1

SW2

UART

OFF

OFF

SD-card

ON

OFF

eMMC

OFF

ON

SPI flash

ON

ON

Flashing a new U-Boot version

U-Boot SPL is provided as file spl/u-boot-spl.bin.normal.out. Main U-Boot is in file u-boot.itb.

Assuming your new U-Boot version is on partition 1 of an SD-card you could install it to the SPI flash with:

sf probe
load mmc 1:1 $kernel_addr_r u-boot-spl.bin.normal.out
sf update $kernel_addr_r 0 $filesize
load mmc 1:1 $kernel_addr_r u-boot.itb
sf update $kernel_addr_r 0x100000 $filesize

For loading the files from a TFTP server refer to the dhcp and tftpboot commands.

After updating U-Boot you may want to erase a saved environment and reboot.

env erase
reset

Booting from SD-Card

The device boot ROM loads U-Boot SPL (u-boot-spl.bin.normal.out) from the partition with type GUID 2E54B353-1271-4842-806F-E436D6AF6985. You are free to choose any partition number.

With the default configuration U-Boot SPL loads the U-Boot FIT image (u-boot.itb) from partition 2 (CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION=0x2). When formatting it is recommended to use GUID BC13C2FF-59E6-4262-A352-B275FD6F7172 for this partition.

Booting from eMMC

The device boot ROM tries to load U-Boot SPL (u-boot-spl.bin.normal.out) from sector 0 of the eMMC’s main hardware partition. But this conflicts with GPT partitioning. Fortunately eMMC can alternatively load U-Boot SPL from a backup position.

For U-Boot SPL (u-boot-spl.bin.normal.out) starting at sector 2048 (position 0x100000) write the following bytes to the eMMC device after GPT partitioning:

Address

Bytes

0x0000

40 02 00 00 00 00 10 00

0x0290

40 02 00 00 00 00 10 00

With the default configuration U-Boot SPL loads the U-Boot FIT image (u-boot.itb) from partition 2 (CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION=0x2). When formatting it is recommended to use GUID BC13C2FF-59E6-4262-A352-B275FD6F7172 for this partition.

Booting from UART

The boot ROM supports the X-modem protocol to upload spl/u-boot-spl.bin.normal.out. U-Boot SPL support loading the FIT image u-boot.itb via the Y-modem protocol.

Due to restrictions of the boot ROM not all X-modem implementations are compatible. The package tio (https://github.com/tio/tio) has been found to be usable.

Debug UART

By default the SBI interface is used for the debug UART. But this only works in main U-Boot. To enable the debug UART in SPL, too, use the following settings:

CONFIG_DEBUG_UART=y
CONFIG_DEBUG_UART_NS16550=y
CONFIG_DEBUG_UART_BASE=0x10000000
CONFIG_SPL_DEBUG_UART_BASE=0x10000000
CONFIG_DEBUG_UART_CLOCK=24000000
CONFIG_DEBUG_UART_SHIFT=2