Re: 2.6.32 regression (bisected): Video tearing/glitching with T400 laptops

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Fri, 02 Oct 2009 18:40:27 -0400
"Theodore Ts'o" <tytso@mit.edu> wrote:

> Hi, 
> 
> In recent kernels, my X display (running with a KMS-enabled X server)
> has been very jittery and with lots of glitching and tearing --- sorry
> if this isn't the correct technical term, not sure what it is --- on
> my T400 Lenovo laptop.   It seems related to what is on the desktop,
> and moving the mouse does seem to affect the rate and percentage of
> the screen which jitters --- which is enough to be very distracting,
> although I can still read the contents of the windows where the screen
> is tearing/glitching/flashing.
> 
> I bisected it down to this commit:
> 
> 74dff282237ea8c0a5df1afd8526eac4b6cee063 is the first bad commit
> commit 74dff282237ea8c0a5df1afd8526eac4b6cee063
> Author: Jesse Barnes <jbarnes@virtuousgeek.org>
> Date:   Mon Sep 14 15:39:40 2009 -0700
> 
>     drm/i915: framebuffer compression for GM45+
>     
>     Add support for framebuffer compression on GM45 and above.
> Removes some unnecessary I915_HAS_FBC checks as well (this is now
> part of the FBC display function).
>     
>     Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
>     Signed-off-by: Eric Anholt <eric@anholt.net>
> 
> ... and taking the latest git mainline, and I confirmed that the
> problem was still present, and then after reverting this commit, the
> problem went away.
> 
> I've included my Xorg.0.log file in case that's helpful.  Please let
> me know if there's anything else you need.

Yeah I've had a couple of other reports of flicker pointing to this
commit... I'll be able to look into it next week.

-- 
Jesse Barnes, Intel Open Source Technology Center