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

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Message-ID: <AANLkTi=_OW5NvnS1oWzt3DW9CPPwNX_sAkPh_QOuXzhv@mail.gmail.com>
Date:	Sat, 4 Sep 2010 19:29:12 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sitsofe Wheeler <sitsofe@...oo.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH] Revert "drm/i915: fix vblank wait test condition"

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.

View attachment "0001-i915-Fix-wrong-resolution-after-boot-problem.patch" of type "text/x-patch" (1341 bytes)