Bug 40883

The reported platform is GM965. Ouping, can you reproduce it?

The bisected commit:
commit d74362c9e45689d8d7e3d4bcf6681c4358ef4f2e
Author: Keith Packard <keithp@keithp.com>
Date:   Thu Jul 28 14:47:14 2011 -0700

    drm/i915: Flush other plane register writes

    Writes to the plane control register are buffered in the chip until a
    write to the DSPADDR (pre-965) or DSPSURF (post-965) register occurs.

    This patch adds flushes in:

    	intel_enable_plane
    	gen6_init_clock_gating
    	ivybridge_init_clock_gating

    Signed-off-by: Keith Packard <keithp@keithp.com>

with the same kernel, run game simutrans, but I can't reproduce the issue, could you please post the System Environment(include libdrm, mesa and Xserver commit). It seems that game simutrans use 2D driver. 
System Environment:
--------------------------
Kernel:     (drm-intel-next)d74362c9e45689d8d7e3d4bcf6681c4358ef4f2e
Libdrm:     (master)2.4.26-3-g2acaf160df584a5ef7b5c5b84819389948cd97ad
Mesa:       (master)00792e3586746c833ffc9bb65712e38038916e06
Xserver:    (master)xorg-server-1.11.0
(In reply to comment #0)
> This report is to track a regression introduced between v3.0 and v3.1-rc1.
> Please don't close it until it has been fixed in mainline.
> Submitter: Philipp Klaus Krause <pkk@spth.de>
> Date: 2011-08-31 08:43:06 +0200
> Message-ID: <4E5DD7FA.9000103@spth.de>
> Reference:
> http://thread.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/5491
> Reference: http://bugs.debian.org/641622
> First-bad-commit: d74362c9e45689d8d7e3d4bcf6681c4358ef4f2e "drm/i915: Flush
> other plane register writes"
>  In the free game simutrans, in fullscreen mode I see the following problem:
>  The lower about 2 cm of the screen don't update. They are black or carry
>  the image from the game startup screen. They flicker once in a while,
>  but otherwise the image stays the same.
> [...]
>  Switching to the console and back or taking a screen shot is a temporary
>  (few seconds) workaround.
>  Using kernel command line i915.i915_enable_fbc=0 is a permanent workaround.

what's more,i915.i915_enable_fbc=0 is default in kernel(commit: d74362c9e45689d8d7e3d4bcf6681c4358ef4f2e).so you didn't use kernel command line i915.i915_enable_fbc=0 in grub.
(In reply to comment #0)
> This report is to track a regression introduced between v3.0 and v3.1-rc1.
> Please don't close it until it has been fixed in mainline.
> Submitter: Philipp Klaus Krause <pkk@spth.de>
> Date: 2011-08-31 08:43:06 +0200
> Message-ID: <4E5DD7FA.9000103@spth.de>
> Reference:
> http://thread.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/5491
> Reference: http://bugs.debian.org/641622
> First-bad-commit: d74362c9e45689d8d7e3d4bcf6681c4358ef4f2e "drm/i915: Flush
> other plane register writes"
>  In the free game simutrans, in fullscreen mode I see the following problem:
>  The lower about 2 cm of the screen don't update. They are black or carry
>  the image from the game startup screen. They flicker once in a while,
>  but otherwise the image stays the same.
> [...]
>  Switching to the console and back or taking a screen shot is a temporary
>  (few seconds) workaround.
>  Using kernel command line i915.i915_enable_fbc=0 is a permanent workaround.

FBC are now disabled again on Ironlake by default.

(And pre-Ironlake!)