How to enable HDMI on Hikey620

Products Support HiKey
#1

Hi all,

I’m trying to connect HDMI display running at 1280x720@60 resolution on: Hikey620 board with Android 9.0 image - Kernel 4.14.77
Hikey 620: HiKey - 96Boards

The problem is that the HDMI display interface seems to be disabled:

$ cat /sys/class/drm/card0-HDMI-A-1/enabled
disabled

I added this line to
$ vi device/linaro/hikey/hikey/BoardConfig.mk
BOARD_KERNEL_CMDLINE += video=HDMI-A-1:1280x720@60.

However, HDMI didn’t display on Hikey620 board.

What do I need to do to enable the external HDMI interface?

Thanks,
Hoa

#2

You shouldn’t have to do anything.

There is one problem that you might be running into, but note that I’m not particularly familiar with the hikey board, just the hikey960. But essentially, the SoC does not have an HDMI interface. Just DSI. And on top of that, the clock signal from the SoC does not comply with the requirements for a fully compliant HDMI signal, so when you call for 1920x1080@60, it actually feeds the HDMI with 1920x1080@58. If your monitor is particularly sensitive, it may reject the signal, and you get no display.

So my suggestion is that you start off by trying it with a bunch of DIFFERENT displays. If you can get one of them to work, then you can go from there. If they ALL do not work, then more debugging is needed.

#3

Thank you for your suggestion.

I tried to test with other resolution at: Monitor Guide for HiKey - 96Boards.

However, HDMI didn’t display.
But in case of Android 9 with kernel 4.9, HDMI displayed normal.