linux-kernel - Re: [4.4-rc1][Regression] drm/i915: Check live status before reading edid

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Message-ID: <571539B3.6060307@canonical.com>
Date:	Mon, 18 Apr 2016 15:46:59 -0400
From:	Joseph Salisbury <joseph.salisbury@...onical.com>
To:	Jani Nikula <jani.nikula@...ux.intel.com>, sonika.jindal@...el.com
Cc:	shashank.sharma@...el.com, rodrigo.vivi@...el.com,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	LaMont Jones <lamont.jones@...onical.com>
Subject: Re: [4.4-rc1][Regression] drm/i915: Check live status before reading
 edid

On 03/28/2016 02:39 PM, Joseph Salisbury wrote:
> On 03/02/2016 04:58 PM, Joseph Salisbury wrote:
>> On 02/29/2016 04:33 AM, Jani Nikula wrote:
>>> On Wed, 24 Feb 2016, Joseph Salisbury <joseph.salisbury@...onical.com> wrote:
>>>> Hi Sonika,
>>>>
>>>> A kernel bug report was opened against Ubuntu [0].  After a kernel
>>>> bisect, it was found that reverting the following commit resolved this bug:
>>>>
>>>> commit 237ed86c693d8a8e4db476976aeb30df4deac74b
>>>> Author: Sonika Jindal <sonika.jindal@...el.com>
>>>> Date:   Tue Sep 15 09:44:20 2015 +0530
>>>>
>>>>     drm/i915: Check live status before reading edid
>>>>
>>>>
>>>>
>>>> The regression was introduced as of v4.4-rc1.
>>>>
>>>> I was hoping to get your feedback, since you are the patch author.  Do
>>>> think increasing the number of tries in intel_hdmi_detect() is worth
>>>> trying?  Do you think gathering any additional data will help diagnose
>>>> this issue, or would it be best to submit a revert request?
>> Thanks for the info.  I will have all of these commits tested.
>>
>>
>>> There are at least the following commits claiming to fix issues in the
>>> above commit. Please make sure you have them.
>>>
>>> BR,
>>> Jani.
>>>
>>>
>>> commit 8d409cb3e8a24196be7271defafd4638f3e0b514
>>> Author: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>>> Date:   Wed Feb 10 19:59:05 2016 +0200
>>>
>>>     drm/i915: Fix hpd live status bits for g4x
>>>
>>> commit 3d8acd1f667b45c531401c8f0c2033072e32a05d
>>> Author: Gary Wang <gary.c.wang@...el.com>
>>> Date:   Wed Dec 23 16:11:35 2015 +0800
>>>
>>>     drm/i915: increase the tries for HDMI hotplug live status checking
>>>
>>> commit 97f9010af05c15e0b7e6b4ef6ff8cb0ebb7e7715
>>> Author: Daniel Vetter <daniel.vetter@...ll.ch>
>>> Date:   Fri Dec 11 19:44:15 2015 +0100
>>>
>>>     drm/i915: mdelay(10) considered harmful
>>>
>>> commit 0f5a9be15797f78c9a34e432f26c796165b6e49a
>>> Author: Imre Deak <imre.deak@...el.com>
>>> Date:   Fri Nov 27 18:55:29 2015 +0200
>>>
>>>     drm/i915: take a power domain reference while checking the HDMI live status
>>>
>>>
>>>
>>>
> Hi Jani,
>
> Applying the following commit did indeed fix the original bug[0]:
>
> commit 8d409cb3e8a24196be7271defafd4638f3e0b514
> Author: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Date:   Wed Feb 10 19:59:05 2016 +0200
>
>     drm/i915: Fix hpd live status bits for g4x
>
>
>
> However, it also introduced a new bug, which is covered in that bug
> report.  The new bug is that after locking/unlocking the screen, all the
> windows get shuffled around in a manner that is consistent with X
> deciding that it's single-headed again, and then back to double headed. 
> This only happens when I build a kernel with both commit 237ed86c AND
> commit 8d409cb3e.  If I revert 237ed86c and keep only 8d409cb3e both the
> original bug and the new bug go away.  Do you think commit 237ed86c is
> still even needed now that 8d409cb3e has landed?  Maybe the new bug is
> due to the interaction between 237ed86c and 8d409cb3e.
>
> Thanks,
>
> Joe
>
> [0] http://pad.lv/1543683
>
>
>
>
>
Hello,

Is there any addition debug data we can collect to debug the new bug
that commit 8d409cb3e introduced?

Thanks,

Joe