萌新求助：树莓派3B+无法引导64位系统

刷的是 openSUSE 15.1 aarch64 rpi3 镜像, Fedora arm64 也一样, 卡在U-Boot进不了系统，输出信息：
Net: No ethernet found.
starting USB......
USB0: scanning bus 0 for devices... 5 USB Device(s) found
scanning usb for storage devices...... 0 Storage Device(s) found
Hit any key to stop autoboot: 0
U-Boot>