Re: [PATCH 3/4] arm64: Juno: Add HDLCD support to the Juno boards.

[Liviu Dudau <Liviu.Dudau@arm.com>]

On Wed, Aug 05, 2015 at 10:48:54PM +0100, Russell King - ARM Linux wrote:
> On Wed, Aug 05, 2015 at 08:03:12PM +0100, Liviu Dudau wrote:
> > I have to confess that I am not entirely up to speed with the TDA19988
> > situation at the moment. Andrew Jackson was dealing with that and
> > working with Jean to get that in the upstream, but his contract has
> > ended and he has moved to other things.
> 
> Umm, I'm the maintainer for TDA998x:
> 
> NXP TDA998X DRM DRIVER
> M:      Russell King <rmk+kernel@arm.linux.org.uk>
> S:      Supported
> F:      drivers/gpu/drm/i2c/tda998x_drv.c
> F:      include/drm/i2c/tda998x.h
> 
> It would be nice if people worked with the actual maintainers of things
> rather than random other people...

Sorry, it was my mistake, I have blindly followed the get_maintainers.pl
generated list of email rather than engage my brain and realise that part
of the patch also affects TDA19988 driver.

> 
> > > Also, the whole question of representing connectors in a DRM model is
> > > yet to be established.  Yes, DT should describe the hardware, but we
> > > don't yet know _how_ to describe physical connectors with stuff
> > > implemented on top of DRM yet, and we have nothing that makes use of
> > > this.
> > 
> > Please help me understand the current situation: you have added
> > support for components that the video drivers can use and the bindings
> > for that are described in Documentation/devicetree/bindings/media/video-interfaces.txt.
> 
> No.  I added the component helpers, which are entirely firmware agnostic.
> The media bindings were created by others, and through development done
> by Pengutronix, they were factored out of media into common DT code and
> re-used for the IMX DRM driver.  The binding document which describes
> that work is not the one you refer to above, but this one:
> 
> Documentation/devicetree/bindings/graph.txt
> 
> This started them as a basis for DRM drivers on ARM - but it's never been
> officially "adopted" as a method to describe DRM drivers - it's only what
> some drivers are using.  It ought to be nailed down as a way to ensure
> inter-operability between components though, but no one has really made
> that decision.

OK, I'm interested on whom do I need to talk to in order for the official
"adoption" to happen here. 

> 
> > According to that document my patch should be compliant once I add the
> > reg= property. Is that something that cannot be used with tda998x driver
> > or is there any other reason why you think the patch is not compliant?
> 
> Jean's proposal to add audio support to the TDA998x driver does it via
> this change to the binding spec:
> 
> +Optional nodes:
> +
> +  - port: up to three ports.
> +       The ports are defined according to [1].
> +
> +    Video port.
> +       There may be only one video port.
> +       This one must contain the following property:
> +
> +       - port-type: must be "rgb"
> +
> +       and may contain the optional property:
> +
> +       - reg: 24 bits value which defines how the video controller
> +               output is wired to the TDA998x input (video pins)
> +               When absent, the default value is <0x230145>.
> +
> +    Audio ports.
> +       There may be one or two audio ports.
> +       These ones must contain the following properties:
> +
> +       - port-type: must be "i2s" or "spdif"
> +
> +       - reg: 8 bits value which defines how the audio controller
> +               output is wired to the TDA998x input (audio pins)
> +
> +[1] Documentation/devicetree/bindings/graph.txt
> 
> (That's not a particularly precise definition, but it's what we have at
> the moment.)
> 
> > If you are referring to connecting an encoder with a HDMI connector, I
> > have tested that and it seems to work, although my situation is simple
> > because there are no options in my setup: one HDLCD connects to one
> > TDA19988 which connects to one HDMI output.
> 
> Right now, the TDA998x will ignore the additional information, but that
> won't be the case with Jean's audio work (see the above binding
> information.)

Yes, I have seen that patchset. I will apply it to my tree and send an
updated version with the port-type property when I send v2.

Best regards,
Liviu

> 
> -- 
> FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
> according to speedtest.net.
> 

-- 
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