No HDMI after kernel upgrade on TInkerboard S (armv7, 32 )

[brendlefly62]

Can someone please point me to a good outline for setting up simple, minimal graphics on armv7 embedded? (our point out what I've done wrong as indicated in liked material (below)?

I had a fully working gentoo system with kernel from gentoo-sources circa 6.1. A few weeks ago, I also had a fully-working 6.6.13 kernel from upstream kernel archives, without gentoo patches.

I currently have a working system that will boot with either kernel 6.6.16 or 6.7.4, built from gentoo-sources, but with no hdmi signal. I can ssh into the board, and things look pretty good, just no video output on hdmi...

I've looked at the gentoo wiki and a number of forum posts on similar problems, but most of those are for x86 or amd64 systems. This is arm (and rockchip, rk3288, not the bcm27-series SoCs in rpis).

My latest kernel is 6.6.16, built from clean gentoo-sources, using a nicley-working armbian system kernel config, copied in as .config before starting kernel build with make menuconfig (changing ONLY four things) and then proceeding with make && make modules_install dtbs_install zinstall. The only things changed from the nicely-running armbian config were -- *-added kernel config support; *-enabled mousedev, ps2 and serial mouse; *-enabled AT/XT keyboard; *-enabled cordic algorithm
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Frankly, I don't need performance graphics from this little board, I just want regular video console working working via the hdmi port, so I can use it to troubleshoot when this normally-headless system needs a more intimate exam...

One more thing -- the armbian kernel uses an initrd. My kernel does not. I imagine the armbian initrd is starting something ... but I haven't (yet) figured out what.

Here's some telemetry --

.config https://paste.gentoo.zip/5TJEuaDn
dmesg https://paste.gentoo.zip/qlXGs3H4
lshw https://paste.gentoo.zip/g5gOZaJv
uboot https://paste.gentoo.zip/5TJEuaDn (serial console output)
fstab https://paste.gentoo.zip/514JAq7e

Thanks