RHELSA 7.1 : X window startup fail with AST2400 VGA installed on AMD Seattle platfrom (A57)

Hi,
I am newbie here,
I have a new AMD ARM project which code name is Seattle, CPU is Cortex A57.
I try to intall RHELSA 7.1 with Aspeed AST2400 VGA card installed,
During the installation process, system pops up an warning message taht "X startup failed, falling back to text mode",
so whole the installation process are under test mode.
Attached is the log info.
OS kernel is : 3.19.0-0.rc5.66.aa7a.aarch64

If I want to install OS under GUI mode, how do I do?
Please help~

Thanks,
Ryan