linux-kernel - Re: [PATCH v2] drm/radeon: Retry DDC probing on DVI on failure if we got an HPD interrupt

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Message-ID: <56616029.1010007@pr.hu>
Date:	Fri, 4 Dec 2015 10:43:05 +0100
From:	Boszormenyi Zoltan <zboszor@...hu>
To:	Christian König <christian.koenig@....com>,
	cpaul@...hat.com, Alex Deucher <alexander.deucher@....com>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:	Jerome Glisse <jglisse@...hat.com>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: Re: [PATCH v2] drm/radeon: Retry DDC probing on DVI on failure if we
 got an HPD interrupt

2015-12-04 09:53 keltezéssel, Christian König írta:
> On 04.12.2015 00:26, cpaul@...hat.com wrote:
>> From: Lyude <cpaul@...hat.com>
>>
>> HPD signals on DVI ports can be fired off before the pins required for
>> DDC probing actually make contact, due to the pins for HPD making
>> contact first. This results in a HPD signal being asserted but DDC
>> probing failing, resulting in hotplugging occasionally failing.
>>
>> This is somewhat rare on most cards (depending on what angle you plug
>> the DVI connector in), but on some cards it happens constantly. The
>> Radeon R5 on the machine used for testing this patch for instance, runs
>> into this issue just about every time I try to hotplug a DVI monitor and
>> as a result hotplugging almost never works.
>>
>> Rescheduling the hotplug work for a second when we run into an HPD
>> signal with a failing DDC probe usually gives enough time for the rest
>> of the connector's pins to make contact, and fixes this issue.
>>
>> Signed-off-by: Lyude <cpaul@...hat.com>
>
> I find a second a bit long, but if it works so what?
>
> Looks sane enough to me, patch is Reviewed-by: Christian König <christian.koenig@....com>

Does this patch help in case of the Radeon chip only has HDMI and DP outputs
exposed (Zotac ZBOXNANO-AQ01) but used with DVI or VGA monitors with
converter cables? We have some problems with such scenarios that sounds
eerily similar to this description.

Inquiry-by: Zoltán Böszörményi <zboszor@...hu>
;-)

Thanks in advance.

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