regression in 2.6.32-rc1 [KMS, I915] git-bisected

[Martin Fahr <maf@gmx.eu>]

Hi,

Linux v2.6.32-rc1 introduced a bug for me, which gives me a black screen 
on my laptop when booting with KMS switched on. Starting X does not 
change that, i.e. I don't get any graphics to see. Except for this, the 
system runs fine, and the backlight of the LCD display is on. If I 
switch KMS off, the system runs perfectly.

I reported this problem before, but did not get any response. In the 
meantime, I used git-bisect to find the responsible commit:
commit e70236a8d3d0a4c100a0b9f7d394d9bda9c56aca
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Mon Sep 21 10:42:27 2009 -0700

     drm/i915: split display functions by chip type

     This patch splits out several of the display functions into a separate
     display function table to avoid tons of chipset specific if..else
     if..else if blocks all over.  There are more opportunities for this
     (some noted in the structure defintition); so more cleanup patches will
     follow.

     Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
     Signed-off-by: Eric Anholt <eric@anholt.net>

Double-checked that by unapplying the commit (KMS works), and reapplying 
it (KMS does not work).

Kernels up to 2.6.34-rc1 do not solve the problem for me, and 
unfortunately, unapplying the patch to v2.6.32 or 2.6.33 results in 
conflicts. Framebuffer console and KMS on 2.6.31 worked fine, only X did 
not cooperate with that.

Any help appreciated, and I will do my best to answer any questions.

Running on Debian testing.

lspci -v:
00:02.0 VGA compatible controller: Intel Corporation 82830 CGC [Chipset 
Graphics Controller] (rev 04) (prog-if 00 [VGA controller])
         Subsystem: Samsung Electronics Co Ltd Device c002
         Flags: bus master, fast devsel, latency 0, IRQ 10
         Memory at e8000000 (32-bit, prefetchable) [size=128M]
         Memory at e0000000 (32-bit, non-prefetchable) [size=512K]
         Expansion ROM at <unassigned> [disabled]
         Capabilities: [d0] Power Management version 1

00:02.1 Display controller: Intel Corporation 82830 CGC [Chipset 
Graphics Controller]
         Subsystem: Samsung Electronics Co Ltd Device c002
         Flags: bus master, fast devsel, latency 0
         Memory at f0000000 (32-bit, prefetchable) [size=128M]
         Memory at e0080000 (32-bit, non-prefetchable) [size=512K]
         Capabilities: [d0] Power Management version 1

Thanks,

Martin


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