linux-kernel - Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to .detect() callback

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Date:	Thu, 4 Aug 2016 14:58:00 +0100
From:	Jose Abreu <Jose.Abreu@...opsys.com>
To:	Russell King - ARM Linux <linux@...linux.org.uk>,
	Jose Abreu <Jose.Abreu@...opsys.com>
CC:	<dri-devel@...ts.freedesktop.org>,
	Carlos Palminha <CARLOS.PALMINHA@...opsys.com>,
	Archit Taneja <architt@...eaurora.org>,
	David Airlie <airlied@...ux.ie>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Takashi Iwai <tiwai@...e.de>,
	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
	Thierry Reding <treding@...dia.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to
 .detect() callback

Hi Russell,

On 04-08-2016 11:47, Russell King - ARM Linux wrote:
> On Thu, Aug 04, 2016 at 11:44:51AM +0100, Jose Abreu wrote:
>> When running HDMI compliance tests we noticed that sometimes
>> the edid changes but the get_modes() function is not called
>> so the edid is not updated. Moving the edid reading to the
>> detect() callback ensures that the edid is correctly updated
>> after an hotplug.
> Wouldn't this be a bug in the higher levels of DRM?
>

I am not sure if this is a bug in DRM or a bad implementation of
dw-hdmi. I've seen at least two more drivers that do the edid
reading at the .detect() callback: nouveau and gma500. This is
noticeable if while sending video the edid changes like in a
compliance environment. In the environment that I tested I was
sending video and swapped an edid that had support for AI packets
to another one without support and I noticed that although the
hotplug is generated the edid was not being updated.

Best regards,
Jose Miguel Abreu