Hi, Lars,
Thank you very much for your reply.
I build all the files myself. This is my steps:
1. check out the u-boot tree form Xilinx.( git clone git://git.xilinx.com/u-boot-xlnx.git) and build the u-boot.elf
2. Do as the reference design to get the uImage, devicetree.dtb and boot.bin.
(The bit files is rebuild with the xps project offered in the reference design package, I did nothing for it, just open the project and export to sdk)
3. build the uramdisk.tar.gz
4.copy all the files into BOOT partition of SD, and untar the ubuntu into rootfs partition of SD
5. boot from the SD in ZC702 board and it hang and get the message I offered.
-- Rain.xiang