RPi4 hdmi support

[Matt P.]

Hi there! I don't usually have anything to contribute, but I noticed something that might make an easy fix for someone that knows a little more than me.

On my RPi4 (4 gig model), the Pi3 images for 12.2-RELEASE and STABLE don't have HDMI out, except for the EFI boot screen which disappears quickly. These images also are supposed to use DHCP, but they never connect to the network, so maybe it doesn't actually boot at all. Guess I need a serial connector to find out.

However, 13.0-CURRENT boots fine. I hoped to avoid CURRENT, though as I'm wanting to use the Pi in production.

In desperation, I decided to try a hack, which I didn't really expect to work. I flashed 12.2-STABLE, then erased the boot directory and copied the 13.0-CURRENT boot directory files to the card. Then 12.2-STABLE could boot and show HDMI, but only up to a handoff to the kernel, which crashed. (Which is what I expected.) But the fact that the HDMI was working was a surprise.

So, could I Frankenstein 12.2 and CURRENT to work? Maybe even just by copying a file? Though I can handle custom compiling if needed.

Attached is my DMESG, though I've been messing with the system so it's not completely stock.
--Matt

PS. You may also notice it only sees 900 Meg of memory on a 4 gig model. I'm not sure what's going on there, but I noticed a similar problem was encountered and fixed on Linux: https://github.com/home-assistant/operating-system/issues/439