linux-kernel - Re: kernel 2.6.37-rc2 breaks i915 graphics

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Date:	Mon, 22 Nov 2010 10:36:16 +0200
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Chris Vine <chris@...ne.freeserve.co.uk>
CC:	Chris Wilson <chris@...is-wilson.co.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kernel 2.6.37-rc2 breaks i915 graphics

On 11/21/2010 08:34 PM, Chris Vine wrote:
> On Sun, 21 Nov 2010 10:30:43 +0000
> Chris Wilson <chris@...is-wilson.co.uk> wrote:
> 
>> On Sun, 21 Nov 2010 10:23:44 +0000, Chris Vine
>> <chris@...ne.freeserve.co.uk> wrote:
>>> Hi,
>>>
>>> With kernel 2.6.37-rc2, i915 graphics usually fails on boot-up after
>>> modesetting with my Lenovo S12 netbook which uses the Intel 945GME
>>> Express Integrated Graphics Controller.  It displays up to the
>>> point at which modesetting takes place and then usually goes blank.
>>>
>>> There may be some kind of race at work here: first, sometimes
>>> (maybe 1 times in 4) graphics comes up correctly on a first cold
>>> boot, but I have never managed to get it to come up on a warm
>>> reboot. Secondly, graphics can be restored when I know (but cannot
>>> see) that boot-up has concluded, simply by suspending the laptop
>>> and then resuming.  Resuming the laptop after a suspend always
>>> brings up the graphics correctly.
>>
>> Add drm.debug=0xe to your boot commandline and compare if there is any
>> difference between a successful cold boot, a broken cold boot and a
>> warm boot. Similarly, comparing the output of intel_reg_dumper after
>> each should yield a few clues as to what stage in the boot process we
>> fail. -Chris
> 
> First an additional datum point: 2.6.37-rc1 works normally, so the bug
> is something introduced between 2.6.37-rc1 and 2.6.37-rc2 (to that
> extent it may be related to this bug which reports a similar phenomenon:
> http://lkml.org/lkml/2010/11/21/23 ).
> 
> Attached is the dmesg output from a successful cold boot with
> 2.6.37-rc2, an unsuccessful cold boot and an unsuccessful warm boot,
> each with drm.debug=0xe.
> 
> I can't provide the output of intel_reg_dumper:  I can't compile the
> latest intel-gpu-tools from git (missing declaration/definition of
> I915_EXE_BLT).  Probably something in a relevant library is too old.
> 
> Chris

Do you know / can do a "git bisect" good 2.6.37-rc1 bad 2.6.37-rc2
should not be that long. This will pinpoint the bug to a specific
patch.

Thanks
Boaz

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