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

[Brice Goglin]

Carl,

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?

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?

thanks,
Brice




Carl Worth wrote:
>  NEWS |   10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> New commits:
> commit e1cace16a6130dcdd93965d2329a349d49200fa6
> Author: Carl Worth <cworth at cworth.org>
> Date:   Wed Apr 15 16:33:12 2009 -0700
>
>     NEWS: Add note about broken PAT code in some kernels
>     
>     Hoping to cut off some false bug reports here.
>
> diff --git a/NEWS b/NEWS
> index c059c98..0d0cd8a 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -19,6 +19,16 @@ this release, which should give the best performance and
>  robustness. When KMS is available, UXA is the default acceleration
>  used by the driver, (EXA is the default otherwise).
>  
> +Known issue:
> +
> +	Some Linux kernel versions (such as 2.6.29) are known to have
> +	broken PAT code that causes recent versions of this driver to
> +	fail, (which can manifest as the X server simply not
> +	starting). This can be verified by adding the "nopat" option
> +	to the kernel command-line and seeing the failure go away. We
> +	hope that newer kernels in the 2.6.29.x as well as 2.6.30 and
> +	above will have working PAT code.
> +
>  Some of the most notable bugs fixed in 2.7.0 include:
>  
>  	[GM45 965GM] bad htotal causes panel startup failure
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