I've opened a dedicated thread for the issue I've initially illustrated here:
https://www.raspberrypi.org/forums/view ... 2#p1579222
Sum up is:
I'm trying to set up a 7" touch screen that communicate through DPI (parallel RGB) to a Raspberrry CM3+.
Everything is working fine with vc4 and Opengl disabled.
Then, If I enable Opengl (Full kms) in rasp-config, display hangs on boot.
It doesn't show four raspberries, it only shows the welcome screen and freezes there.
I can remotely log in with ssh and everything else is working fine, only the display seems to be freezed.
I've tried also different config.txt options looking for suggestions in other threads but nothing worked.
It turned out that I was missing something: vc4 ignores display settings in config.txt
Moderator "6by9" gave the following answer:
Now I'm tryng to follow his suggestion.vc4-kms-v3d replaces ALL display configuration that is present in config.txt with kernel configuration.
You need to add device tree configuration and a kernel driver to configure your DPI output.
https://github.com/raspberrypi/linux/bl ... verlay.dts is a suitable overlay that configures the Adafruit Kippah with their 800x480 panels.
In that case the panel is defined as being a yx700wv03.
https://github.com/raspberrypi/linux/bl ... le.c#L1847 to line 1874, and lines 2531-2, then convert that name into a panel mode.
Will post here results with the purpoise to help someone else in my same situation.