(In reply to Chris Bainbridge from comment #8)

> So suggest enabling debug log and compare those two lines from a working and
> non-working kernel.

Done (see previous message) :-)

> It should also be trivial to checkout a recent tag and revert the bad commit

Done :-)
Reverted the bad commit on current 4.6.0-rc6+ an tested
and it worked like a charm !! no display problems anymore

> (there is a conflict but just delete the avivo_get_fb_ref_div function to
> resolve it).

I did, and thanks to your directions it all worked out perfectly :-)