[2.6.39 regression] i915/kms: garbled screen because of 49183b281 (was: Re: Linux 2.6.39-rc7)

[Melchior FRANZ]

* Chris Wilson -- Thursday 12 May 2011:
> So we think that enabling the plane at this point is masking a bug in our
> modeset, or that some side-effect of writing those registers or waiting
> for that vblank has a vital latching or delay that we have not accounted
> for.

Attached are the requested register dumps:

  intel_reg_dump__nomodeset.gz
          \___no kms -- no corruption

  intel_reg_dump__bad.gz
          \___with kms -- corrupted screen contents with staircase
              shaped and horizontally stretched scan lines. Unreadable.

  intel_reg_dump__lid.gz
          \___after closing and reopening lid. The text is now readable,
              but horizontally stretched. It looks like there's a dark
              pixel between any pair of legitimate font pixels.

  intel_reg_dump__x11.gz
           \___after starting x11. Now both the x11 screen and virtual
               terminals look right.


(BTW: there's also still the problem that the backlight remains off
until I press the "screen darker" key. Maybe this problem is related?
https://bugzilla.kernel.org/show_bug.cgi?id=31522).

m.
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