linux-kernel - Re: [Intel-gfx] Bad flicker on skylake HQD due to code in the 4.7 merge window

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Date:	Sat, 2 Jul 2016 08:24:31 +0200
From:	Thorsten Leemhuis <regressions@...mhuis.info>
To:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:	Jani Nikula <jani.nikula@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	"Syrjala, Ville" <ville.syrjala@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: Re: [Intel-gfx] Bad flicker on skylake HQD due to code in the 4.7
 merge window

On 23.06.2016 13:25, James Bottomley wrote:
> On Tue, 2016-06-21 at 17:00 -0400, James Bottomley wrote:
>> On Tue, 2016-06-21 at 18:44 +0300, Ville Syrjälä wrote:
>>> On Tue, Jun 21, 2016 at 09:53:15AM -0400, James Bottomley wrote:
>>>> On Mon, 2016-06-20 at 11:03 +0300, Jani Nikula wrote:
>>>>> Cc: Ville
>>>>>
>>>>> On Mon, 20 Jun 2016, James Bottomley <
>>>>> James.Bottomley@...senPartnership.com> wrote:
>>>>>> OK, my candidate bad commit is this one:
>>>>>>
>>>>>> commit a05628195a0d9f3173dd9aa76f482aef692e46ee
>>>>>> Author: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>>>>>> Date:   Mon Apr 11 10:23:51 2016 +0300
>>>>>>
>>>>>>     drm/i915: Get panel_type from OpRegion panel details
>>>>>>
>>>>>> After being more careful about waiting to identify flicker, 
>>>>>> this one seems to be the one the bisect finds.  I'm now 
>>>>>> running v4.7-rc3 with this one reverted and am currently 
>>>>>> seeing no flicker problems.   It is, however, early days 
>>>>>> because the flicker can hide for long periods, so I 'll wait 
>>>>>> until Monday evening and a few reboots before declaring
>>>>>> victory.
>>>>>
>>>>> If that turns out to be the bad commit, it doesn't really 
>>>>> surprise me, and that in itself is depressing.
>>>>
>>>> As far as I can tell, after running for a day with this reverted,
>>>> this is the problem.  The flicker hasn't appeared with it 
>>>> reverted.  It's pretty noticeable with this commit included.
>>>
>>> Hmm. The only difference I can see is low vs. normal vswing. Panel 
>>> 0 has low, panel 2 has normal. So either the VBT or opregion is
>>> telling utter lies, or there's some other bug in our low vswing
>>> support.
>>>
>>> To confirm it's really a vswing issue, you should be able to run 
>>> with i915.edp_vswing=2 without flickers on the broken kernel.
>>
>> Preliminary boot indicates no flicker with the bad commit included 
>> and this option, but I'll have to run for quite a bit longer to 
>> verify, since it can sometimes be elusive.
> 
> Two days of runtime seems to confirm this is the problem (still no
> flicker issues).

This issue is listed in my regression reports for 4.7 and I wonder what
the status is. It seems nothing happened for more then a week now, which
is a bad sign as 4.7 final seems only a week or two away.

CU, Thorsten