I am working on H96 Max+ / T9 (RK3328) support for master (Rockchip: add H96 Max+ support by easybe · Pull Request #4195 · LibreELEC/LibreELEC.tv · GitHub).
I think the problem that I am currently facing (vdd_logic too low, see PR comments) is related to the fact that devfreq does not seem to be loaded for the GPU (/sys/class/devfreq/ff300000.gpu/ is empty). With the old rockchip-linux images I have it. Is this even available with the mainline kernel? Any hints what I am missing here?