2 Years ago I created a Raspberry Pi Image for the Compute Module with a custom kernel, 2 custom device overlays, and a custom root file system. I added a plymouth splash screen using an initramfs and tweaked the boot parameters in /boot/config.txt.
I now bought a Compute Module 3 and flashed it with this older image that worked on the Compute Module 1.
When the Compute Module 3 boots with this older image, the connected HDMI LCD just shows the famous Rainbow splash screen from the boot loader and then hangs.
I mounted the latest raspbian image as a loop device on Ubuntu and examined the FAT /boot partition. I compared it versus the older image's /boot partition. There are many differences, including updated device trees for the CM3 and updated boot loader binaries.
I mounted the older image as well and pulled over the newer boot loader binaries, device trees, and I modified the config.txt to include my custom device tree overlays. I kept the kernel.img the same. This did not boot either.
How can I achieve running my older image on the new CM3 without redoing a lot of the work to make that older image custom?
I'd be OK with rebuilding the Kernel with the custom drivers if I could keep my Root File System and the custom software located on it.
Thanks for any suggestions / input.