linux-kernel - Re: [PATCH] Revert "drm/i915: fix vblank wait test condition"

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Message-ID: <4C834DB5.3070702@kernel.org>
Date:	Sun, 05 Sep 2010 10:58:45 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Sitsofe Wheeler <sitsofe@...oo.com>
CC:	Sven Joachim <svenjoac@....de>, Hugh Dickins <hughd@...gle.com>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH] Revert "drm/i915: fix vblank wait test condition"

  On 5.9.2010 1.44, Sitsofe Wheeler wrote:
> On Sat, Sep 04, 2010 at 10:42:46PM +0200, Sven Joachim wrote:
>> On 2010-09-04 21:54 +0200, Hugh Dickins wrote:
>>
>>> On Sat, 4 Sep 2010, Pekka Enberg wrote:
>>>> On Sat,  4 Sep 2010 11:17:14 +0300, Pekka Enberg<penberg@...nel.org>  wrote:
>>>>>> This reverts commit 9559fcdbff4f93d29af04478bbc48294519424f5. The commit causes
>>>>>> wrong screen resolution on some i915 machines such as MacBook which is a
>>>>>> regression from 2.6.35. The issue has been reported multiple times but no fix
>>>>>> has emerged:
>>>> On Sat, Sep 4, 2010 at 12:21 PM, Chris Wilson<chris@...is-wilson.co.uk>  wrote:
>>>>> NAK. You can't simply hide one bug by introducing a much bigger one.
>>>> Dude, it's a nasty regression from 2.6.35. What exactly are you NAK'ing here?
>>>>
>>>>> As you have an affected machine, find which wait_for_vblank() needs to be
>>>>> replaced with a msleep(20|50).
>>>> The attached patch fixes things here. I'm not a drm developer so I
>>>> don't know if it makes technical sense.
>>> Many thanks to you, Pekka: I also don't know if it makes technical sense,
>>> but it solves the same issue for me, so I can at last use 2.6.36-rc on
>>> this laptop.
>> Helps for me as well, but I cannot judge whether it makes technical
>> sense either.  Thanks, Pekka!
> Sadly this doesn't help my EeePC 900 with an i915 when it is booted with
> a battery inside or after doing a suspend to ram (running
> modetest/xrandr in these situations says VGA is connected when there
> isn't even a cable attached).
I haven't heard of this problem. Is it reported on LKML? Is it a 
regression from 2.6.35?

             Pekka
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