[Intel-gfx] xf86-video-intel: NEWS

Carl Worth cworth at cworth.org
Thu Apr 16 18:57:09 CEST 2009


On Thu, 2009-04-16 at 09:28 +0200, Brice Goglin wrote:
> Could you clarify a bit what's going on with PAT and MTRR in recent
> kernels and intel drivers? Apart from PAT being broken, how are things
> supposed to be setup?

I'm actually not too clueful about this stuff. I just know that I hit
PAT bugs once and couldn't start my X server until I booted with "nopat"
so I wanted to make sure there was a good note about that in the release
notes.

> It looks like many Debian bug reports with latest intel drivers are
> related to a WC MTRR disappearing, likely when upgrading to 2.6.29. PAT
> is disabled at _build_time_ in Debian's 2.6.29 (CONFIG_X86_PAT=n) so
> obviously ioremap_wc never works, and a MTRR is thus needed.  Did the
> kernel DRM drivers stop setting MTRR at all assuming that ioremap_WC/PAT
> always works? Who is actually deciding whether MTRR and/or PAT should be
> used? ddx? drm? i915?

So, from asking Eric about this, without PAT, then things should work
with an MTRR. And the DRM driver did not stop setting an MTRR, (it
actually started setting an MTRR as of 2.6.28). And if clarification
beyond that is needed, hopefully Eric will jump in and help out.

-Carl

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