linux-kernel - Re: [PATCH v2 15/28] drm/i2c: tda998x: use the tda998x video format when cea mode

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Message-ID: <20140113174631.GC15937@n2100.arm.linux.org.uk>
Date:	Mon, 13 Jan 2014 17:46:31 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jean-Francois Moine <moinejf@...e.fr>
Cc:	Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org,
	Dave Airlie <airlied@...il.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 15/28] drm/i2c: tda998x: use the tda998x video
	format when cea mode

On Mon, Jan 13, 2014 at 06:24:55PM +0100, Jean-Francois Moine wrote:
> On Mon, 13 Jan 2014 16:35:01 +0000
> Russell King - ARM Linux <linux@....linux.org.uk> wrote:
> 
> > Ah, I see.  It's a thread about your DRM driver, and about the lack of
> > audio on 1080 resolutions.  Taking it in context, the reported issue
> > appears to be lack of video when 1080p is selected, but the display
> > doesn't support 1080p.  That's hardly surprising.
> > 
> > Then rabeeh posts his message about lack of audio at 1920x1080.
> > 
> > Well, I can say that with the tda998x as it stands, the 1080* modes
> > work with audio with armada-drm, so there's no need to change this.
> 
> My DRM driver also has audio with and without the cea mode for all
> resolutions. At the time of Rabeeh's message, I just had forgot to
> switch the audio pins...
> 
> So, TDA998x CEA mode or not?

Firstly, why change something which isn't broken?

Secondly, you need to justify this change by explaining why it is
beneficial to use the internally programmed modes rather than programming
the timings to match the adjusted settings from DRM.

Thirdly, one of your previous patches changed the programming to use the
adjusted mode settings, which may be the CEA mode with slight tweaks.
Have you considered the implication of the hardware generating the video
being programmed with those tweaks vs the encoder using a fixed set of
unadjusted timings?

I'm not convinced that we need this patch at the present time, and I'm
not convinced that we need to introduce a load of tables for no
measurable gain.

-- 
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Estimate before purchase was "up to 13.2Mbit".
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