linux-kernel - Re: [PATCH 2/3] drm/radeon: Fix Asus M2A-VM HDMI EDID error flooding problem

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Date:	Tue, 26 Jul 2011 10:52:05 -0400
From:	Alex Deucher <alexdeucher@...il.com>
To:	Dave Airlie <airlied@...il.com>
Cc:	reimth@...glemail.com, Dave Airlie <airlied@...hat.com>,
	Mario Kleiner <mario.kleiner@...bingen.mpg.de>,
	Jean Delvare <khali@...ux-fr.org>,
	Tyson Whitehead <twhitehead@...il.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	stable@...nel.org, Thomas Reim <rdratlos@...oo.co.uk>
Subject: Re: [PATCH 2/3] drm/radeon: Fix Asus M2A-VM HDMI EDID error flooding problem

On Tue, Jul 26, 2011 at 9:20 AM, Dave Airlie <airlied@...il.com> wrote:
> On Thu, Jul 7, 2011 at 3:01 PM, Alex Deucher <alexdeucher@...il.com> wrote:
>> On Wed, Jul 6, 2011 at 7:30 PM,  <reimth@...glemail.com> wrote:
>>> From: Thomas Reim <rdratlos@...oo.co.uk>
>
> Guys I really still hate this :-)
>
> Other OSes must deal with this sort of thing and I can't say they
> don't do it like this but I can't say for certain this feels like the
> right answer.
>

I emailed the closed driver display team, but as the issue seems to
only afflict certain rs690/rs740 boards, I'm not sure anyone will
remember what quirks those boards had as they are about 5 generations
old at this point.

> My thinking is that we could probably just trust the hot plug detect
> if its reported on HDMI and DVI-D connectors, we still need to poll
> DVI-D as the VGA->DVI convertors don't often assert hpd.
>
> Am I missing something that this wouldn't fix?

The issue in this case is that the problematic connectors don't have
HPD pin wired up and the ddc lines seem to be wired improperly so a
ddc probe always reports something connected unless you actually look
at the EDID header.  For DVI-I we probably have to poll since only the
digital portion will assert hpd in most cases.

Alex
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