[Bug 54877] [bisected] rendering corrupted for windows larger than 2048 pixels in one dimension

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=54877

--- Comment #4 from Alex Deucher <agd5f at yahoo.com> 2012-09-14 13:47:19 UTC ---
(In reply to comment #3)
> (In reply to comment #2)
> > Created attachment 67121 [details] [review] [review]
> > fix
> > 
> > This fixes it.  I need to find out how the quant mode affects the range of
> > values.
> 
> My guess is that QUANT_MODE determines the position of fixed point for internal
> calculations in hw. Quantization precision 1/4096 means 12 bits, and it looks
> like we have 11 bits before the point in that case, with 23 bits total. So if
> we need to increase the range, we have to move the point lowering the
> precision.
> 
> I've tried 1/256 and other values on evergreen for initial implementation of
> that patch in hope that it'll be enough, but IIRC 1/4096 fixed more tests
> (though possibly some test results were simply random). If some tests are
> really failing due to lower precision, I guess we might want to adjust
> QUANT_MODE dynamically.

That makes sense.  The hw worked similarly on r300-r500.  We should adjust the
mode based on the size of the buffer I suppose.

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