[Intel-gfx] i915 / 3.15 intermittently boots into blank screeen

[Jan Niggemann]

Am 29.07.2014 23:35, schrieb Daniel Vetter:
> On Tue, Jul 29, 2014 at 11:09 PM, Jan Niggemann <jn at hz6.de> wrote:
>> Am 18.07.2014 18:25, schrieb Daniel Vetter:
>>>
>>> On Fri, Jul 18, 2014 at 4:49 PM, Jan Niggemann <jn at hz6.de> wrote:
>>>
>>>>
>>>> Am 18.07.2014 15:27, schrieb Daniel Vetter:
>>>>>
>>>>>
>>>>> On Thu, Jul 17, 2014 at 10:31:30PM +0200, Jan Niggemann wrote:
>>>>>>
>>>>>>
>>>>>> I'm experiencing an issue with 3.15.5 on my Lenovo T400:
>>>>>> Since 3.15 (or 3.14, can't say for sure), the boot starts 
>>>>>> normally, but
>>>>>> the
>>>>>> first mode change doesn't occur, resulting in a black screen 
>>>>>> with
>>>>>> backlight
>>>>>> on. The system is entirely unresponsive and I can only press the 
>>>>>> power
>>>>>> button until to switch it off.
>>>>>
>>>>>
>>>>> I think the only way to move forward here is to double-check that 
>>>>> 3.14
>>>>>
>>>>> works and 3.15 is broken by recompiling with the same .config
>>>>> (occasionally config changes cause regressions). And then do a 
>>>>> full git
>>>>> bisect to find the offending commit.
>>>>
>>>>
>>>> thank you for the feedback.
>>>> I still have all my custom built kernels, I will test 3.14.0 
>>>> through
>>>> 3.14.8
>>>> to make sure those were OK and report back.
>>>
>>>
>>> You only need to test 3.14.0, since the backported fixes only 
>>> contain
>>> a very small subset of all patches for 3.15. So it's more efficient 
>>> to
>>> then switch to git bisect between 3.14 and 3.15 directly (after 
>>> you've
>>> confirmed that 3.15.0 is indeed busted).
>>
>> I familiarized with git bisect, that was something I had never used 
>> before.
>>
>> I started it with "git bisect start v3.15 v3.14 -- 
>> drivers/gpu/drm/i915"
>>
>> This lead me to this:
>>
>> cfa7c862982b431add7f2b362526bf31372fc7b0 is the first bad commit
>> commit cfa7c862982b431add7f2b362526bf31372fc7b0
>> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
>> Date:   Tue Apr 29 11:53:58 2014 +0200
>>
>>     drm/i915: Sanitize the enable_ppgtt module option once
>>
>>     Otherwise we'll end up spamming dmesg on every context creation 
>> on snb
>>     with vt-d enabled. This regression was introduced in
>>
>>     commit 246cbfb5fb9a1ca0997fbb135464c1ff5bb9c549
>>     Author: Ben Widawsky <benjamin.widawsky at intel.com>
>>     Date:   Fri Dec 6 14:11:14 2013 -0800
>>
>>         drm/i915: Reorganize intel_enable_ppgtt
>>
>>     As the i915.enable_ppgtt is read-only it cannot be changed after 
>> the
>>     module is loaded and so we can perform an early sanitization of 
>> the
>>     values.
>>
>>     v2:
>>     - Add comment and pimp commit message (Chris)
>>     - Use the param consistently (Jani)
>>
>>     v3:
>>     - Fix init sequence on pre-gen6 by moving the sanitize_ppgtt 
>> call to
>>       gtt_init. Fixes boot hangs on pre-gen6.
>>     - Add a debug output for the sanitize ppgtt mode.
>>
>>     References: https://lkml.org/lkml/2014/4/17/599
>>     Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77916
>>     Cc: Alessandro Suardi <alessandro.suardi at gmail.com>
>>     Cc: Ben Widawsky <ben at bwidawsk.net>
>>     Cc: Chris Wilson <chris at chris-wilson.co.uk>
>>     Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
>>     Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>>     Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>>
>> :040000 040000 5488e397a1aaa28dca4a252452e9463b0a8f8d10
>> 214c8e98b3c72844e48ab7aef02cba7daf139fab M      drivers
>>
>> I realized that the issue does always show, contrary to the subject
>> initially chosen.
>>
>> Unfortunately I can't say anything else, but maybe this will help 
>> you
>> experts spot the issue.
>> If I can help more, be it with testing or anything else, just let me 
>> know.
>
> Hm, I'm not aware of this breaking any gm45 machines, mine here is
> still happy. Can you please make sure that you don't have any i915
> module options set anywhere, either on the kernel cmdline, modeprobe
> config files in /etc or anywhere else?
My kernel cmdline doesn't have anything, but 
/etc/modprobe.d/i915-kms.conf exists. Its content is this single line: 
options i915 modeset=1
Can't remember if I created that (it's from 2010) or if it's Debian 
default...
grep -Ri i915 /etc/ doesn't show anything else.

grep 915 config-3.15
CONFIG_DRM_I915=m
CONFIG_DRM_I915_KMS=y
CONFIG_DRM_I915_FBDEV=y
# CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT is not set
# CONFIG_DRM_I915_UMS is not set
CONFIG_SND_HDA_I915=y

Would it help if I included the driver instead of building a module?

--jan