(In reply to comment #3)
> Created attachment 86598 [details] [review] [review]
> use hw generated cts and n values rather than the sw programmed values
> 
> Does this patch help?  If not, it may be worth adding some slop to the
> r600_hdmi_predefined_acr[] table to handle rounding differences so the
> appropriate defined values get selected.

On some early R6xx the hardware generation of CTS/N values didn't worked
reliable, that's why I've done it like fglrx and calculated the values
manually/used a table for it.