Err, did you call "avivotool regs hdmi" as I asked?

It should return something like:

Audio clocks:
EVERGREEN_AUDIO_PLL1_MUL        00000000
EVERGREEN_AUDIO_PLL1_DIV        00000001
EVERGREEN_AUDIO_PLL1_UNK        00000070

which is the most interesting part for us.

Of course on R6xx hardware it won't start with EVERGREEN_*