[Intel-gfx] Workaround for flicker with panning on the i830 - found a way for tiled displays

[Thomas Richter]

Hi Daniel, hi others,

did even more experiments. I guess I understand now better. Indeed, the 
trouble seems to be the watermark levels. I played more
with all that, and the real culprit seems to be the FW_BLC register 
controlling the watermarks.

On the i830 with the current settings, it is defined to be 0x1080304 
which sets the watermark a bit too low. If I set it to
0x1080306 instead, I get a stable display in all panning positions 
(hurray!).

I would like to fix this, but I guess I would need to understand the 
logic a little bit better. At the time being, you probably better
put the linear frame buffer workaround on hold, it looks I really got 
something here.

Greetings,
     Thomas