Upgraded from 19.08 to 19.12 and monitor stopped working

Hi. I installed Manjaro for the first time today, and used 19.12.

On initial boot my monitor didn't get a chance to display any text at all (i.e. there's no sign of a boot loader). Instead, my monitor switches to a message saying it can't display the video mode.

It's a Dell monitor whose native resolution is 1600x1200 at 60Hz.

I'd seen a video online of somebody installing 19.08 on the same hardware, so I tried installing that instead. It booted fine, installed smoothly, and I created a user account.

Then I ran pacman -Syu (which went smoothly) and rebooted. Again, my monitor says it can't display the video mode.

Has anything changed in the pre-login graphics mode between 19.08 and 19.12?

And how I could edit the startup files to get it running a basic text mode during bootup? I can ssh in to fiddle with the settings fairly easily.

One last thing — this is Manjaro ARM on a Raspberry Pi 4. I didn't post this in the ARM forum as I suspect that the problem is caused by a change to the features between Manjaro 19.08 and 19.12. If I'm wrong about that, feel free to move it...

Cheers!

Yes.
Both the bootloader firmware from Raspberry Pi and the kernel has changed alot between those images.

The file controlling it is in /boot/config.txt

You probably need to define your monitors EDID for it. There are a lot of threads on the forum with the same issue and I believe @Darksky has a pretty good solution for it.

The below post is for a different resolution though.

Thanks @Strit, that was exactly what I needed. It's working beautifully now.

I really like that you can configure just one of the HDMI ports on the Pi 4 to use a given mode.

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