As much as memset clears amuse me, I have to nak this patch as is. The
memset you are using doesn't properly account for the Y-tiled format of the
MCs buffer for certain surface sizes. I can explain more later but the
short version is that the total_height parameter we have in
intel_mipmap_tree m
Fast color clears simply fill the MCS buffer with 0xff. If the MCS BO
is not busy, we can map it without stalling and simply use memset to do
that, without having to reprogram the entire GPU, draw rectangles, and
invoke pixel shaders. This is presumably cheaper.
This code was swiped from intel_m
