Thanks for your help. Another issue is that whether below branch supports HDMI out? I'm using arch/arm64/configs/defconfig and found no output on HDMI display. https://github.com/96boards-hikey/linux/tree/hikey-mainline-rebase-4.4
HDMI should work. At least, you should be able to see there are Text mode output in the HDMI display, right? (If you didn't see any text output, let me know.)
For graphics UI to work, you need to update 'xf86-video-armsoc'. Since in latest hikey-mainline-rebase (-4.4), DRM was updated and name is changed. So, you need git clone and build this in your hikey:
# git clone https://github.com/xin3liang/xf86-video-armsoc/ # cd xf86-video-armsoc/ # git checkout hikey-kirin # cat README ; here you need to follow the last three lines to build & install for hikey
... build & install
BTW, HDMI works well when I tested 3.18 kernel.
BR, Liming Wang