[Intel-gfx] [PATCH] Watermark level workaround for i830

[Thomas Richter]

Hi Daniel, hi intel experts,

please find a patch attached concerning the watermark levels on the i830 
chipsets.

I did a couple of experiments this morning and found that the watermark 
on i830 may neither be
too small (i.e. the FW_BLC register values may not be too high) as 
otherwise the FIFO runs try, but
for some strange reasons, the watermark may neither be too high (the 
FW_BLC register must not
be too small) as otherwise the display flickers. Reasons for this are 
unclear at this moment, though
the attached patch seems to remove flickering quite reliably on linear 
and tiled displays.

What I should probably also report is that the watermark is set quite 
too low (i.e. much too conservative)
on the R31. The computed values are 1 and 5 (for VGA and LVDS, 
respectively), though the minimum
required levels are much higher, somewhere in the ballpark of 32.

Greetings,
     Thomas

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