Re: [PATCH v4 5/6] dt-bindings: display: sii902x: Add HDMI audio bindings

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Jyri Sarha <jsarha@ti.com>
Cc: fabrizio.castro@bp.renesas.com, devicetree@vger.kernel.org,
	architt@codeaurora.org, Songjun.Wu@atmel.com,
	dri-devel@lists.freedesktop.org, peter.ujfalusi@ti.com,
	tomi.valkeinen@ti.com, voice.shen@atmel.com
Subject: Re: [PATCH v4 5/6] dt-bindings: display: sii902x: Add HDMI audio bindings
Date: Sun, 21 Apr 2019 02:12:03 +0300	[thread overview]
Message-ID: <20190420231203.GC4964@pendragon.ideasonboard.com> (raw)
In-Reply-To: <70d217c1-801f-dd4e-a37e-4d4a8550293f@ti.com>

Hi Jyri,

On Tue, Mar 19, 2019 at 04:38:45PM +0200, Jyri Sarha wrote:
> On 17/03/2019 18:16, Laurent Pinchart wrote:
> > On Thu, Mar 14, 2019 at 01:27:51PM +0200, Jyri Sarha wrote:
> >> The sii902x chip family supports also HDMI audio. Add binding for
> >> describing the necessary i2s and mclk wiring for it.
> >>
> >> Signed-off-by: Jyri Sarha <jsarha@ti.com>
> >> ---
> >>  .../bindings/display/bridge/sii902x.txt       | 33 +++++++++++++++++++
> >>  1 file changed, 33 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/display/bridge/sii902x.txt b/Documentation/devicetree/bindings/display/bridge/sii902x.txt
> >> index c4c1855ca654..1a37bbe7c597 100644
> >> --- a/Documentation/devicetree/bindings/display/bridge/sii902x.txt
> >> +++ b/Documentation/devicetree/bindings/display/bridge/sii902x.txt
> >> @@ -9,6 +9,33 @@ Optional properties:
> >>  	  about hotplug events.
> >>  	- reset-gpios: OF device-tree gpio specification for RST_N pin.
> >>  
> >> +	HDMI audio properties:
> >> +	- i2s-data-lanes: Array of up to 4 integers with values of 0-3
> >> +	   Each integer indicates which i2s pin is connected to which
> >> +	   audio fifo. The first integer selects i2s audio pin for the
> >> +	   first audio fifo#0 (HDMI channels 1&2), second for fifo#1
> >> +	   (HDMI channels 3&4), and so on. There is 4 fifos and 4 i2s
> >> +	   pins (SD0 - SD3). Any i2s pin can be connected to any fifo,
> >> +	   but there can be no gaps. E.g. an i2s pin must be mapped to
> >> +	   fifo#0 and fifo#1 before mapping a channel to fifo#2.
> >> +	   I2S HDMI audio is configured only if this property is found.
> > 
> > This looks good to me, but shouldn't the property be defined somewhere
> > in Documentation/devicetree/bindings/sound/ ? The sound bindings seem to
> > be a bit messy though, with little common or high-level documentation,
> > so I don't want to ask you to fix all that :-) Maybe just adding a
> > common-i2s.txt file there would be enough ? 
> > 
> > Apart from this the rest looks good to me, but I'd appreciate if it
> > could be reviewed by audio people.
> > 
> When I think about this property, it hardly is a generic enough to for
> all i2s devices or even codecs. That would probably require gaps in the
> i2s-data-lane order.

We can start by documenting it without gaps allowed, and then allow gaps
if needed, leaving the support of gaps defined in device bindings.

> I would not want to create common-i2s.txt just for this property. The
> is some many other properties that should be added there first. Maybe
> this should be made vendor specific property after all.

You don't need to populate common-i2s.txt with all I2S properties.
Creating the file for i2s-data-lanes would be a nice first step, you can
then let other audio developers take over :-)

> I think I make a resend with alsa-devel included.

-- 
Regards,

Laurent Pinchart
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