How to use SPL to boot u-boot

I download u-boot-2022.04 source file from github—“”.
I successfully to compile the u-boot project with the follow command:
$ make rock-pi-4-rk3399_defconfig
$ export BL31=/home/xuhongjian/my_optee/u-boot-rockchip-u-boot-rockchip-20220318/bl31.elf
$ make CROSS_COMPILE=aarch64-linux-gnu- all
Then I use dd command to write SD card:
$ sudo dd if=idbloader.img of=/dev/sdb seek=64
$ sudo dd if=u-boot.itb of=/dev/sdb seek=16384
but the board cannot boot to u-boot. Did I miss some steps?