linux-kernel - Re: [3.4 regression] [bisected] DisplayPort fails to come on

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Date:	Thu, 14 Jun 2012 19:27:08 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	"Wouter M. Koolen" <W.M.Koolen-Wijkstra@....nl>
Cc:	Dave Airlie <airlied@...il.com>, intergalactic.anonymous@...il.com,
	len.brown@...el.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	"Barnes, Jesse" <jbarnes@...tuousgeek.org>,
	"Wilson, Chris" <chris.wilson@...el.com>
Subject: Re: [3.4 regression] [bisected] DisplayPort fails to come on

On Thu, Jun 14, 2012 at 7:14 PM, Wouter M. Koolen
<W.M.Koolen-Wijkstra@....nl> wrote:
> On 06/14/2012 03:48 PM, Wouter M. Koolen wrote:
>>
>> In the mean while I will redo the bisect.
>
> Hi guys,
>
> I did a bisect on the actual problem (and not on the maybe-related second
> error message). It results in 092945e11c5b84f66dd08f0b87fb729715d377bc:
>
> Author: Adam Jackson <ajax@...hat.com>  2011-07-26 20:39:45
> Committer: Daniel Vetter <daniel.vetter@...ll.ch>  2012-01-17 15:46:56
> Parent: 6919132e7a307b1f181d7655b3ef64cc7581a5ef (drm/i915/dp: Tweak auxch
> clock divider for PCH)
> Branches: linux-3.4.y, remotes/origin/linux-3.4.y, remotes/origin/master
> Follows: v3.2-rc6
> Precedes: v3.4-rc1
>
>    drm/i915/dp: Use auxch precharge value of 5 everywhere
>
>    The default in the Sandybridge docs is 5, as on Ironlake, and I have no
>    reason to believe 3 would work any better.
>
>    Signed-off-by: Adam Jackson <ajax@...hat.com>
>    Acked-by: Jesse Barnes <jbarnes@...tuousgeek.org>
>    Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
>
> I guess there is your reason for 3 :)
>
> Any advice on how to proceed would be very helpful.

Well, can you revert this patch (or just replace the 5 with 3 in the
code) on top of latest 3.4.x and test whether this is indeed the cause
of your regression? Just to make sure that we have the right culprit.

Thanks, Daniel
-- 
Daniel Vetter
daniel.vetter@...ll.ch - +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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