linux-kernel - Re: [PATCH 1/2] dt-bindings: drm/bridge: anx7625: Add a perporty to change TDM setting

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Message-ID: <CAHc4DN+mCbBuB3D9kB2x8HYj9iaX7t6Q4Qjj7hotH3u=eAHJSg@mail.gmail.com>
Date: Fri, 3 May 2024 14:58:16 +0800
From: Hsin-Te Yuan <yuanhsinte@...omium.org>
To: Conor Dooley <conor@...nel.org>
Cc: Hsin-Te Yuan <yuanhsinte@...omium.org>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Xin Ji <xji@...logixsemi.com>, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: drm/bridge: anx7625: Add a perporty to
 change TDM setting

On Thu, May 2, 2024 at 10:47 PM Conor Dooley <conor@...nel.org> wrote:
>
> On Thu, May 02, 2024 at 09:03:31AM +0000, Hsin-Te Yuan wrote:
> > Add a perporty to indicate whether anx7625 should shift the first audio
> > data bit. The default TDM setting is to shift the first audio data bit.
> >
> > Signed-off-by: Hsin-Te Yuan <yuanhsinte@...omium.org>
> > ---
> >  .../devicetree/bindings/display/bridge/analogix,anx7625.yaml          | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> > index a1ed1004651b9..915d5d54a2160 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625yaml
> > +++ b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625yaml
> > @@ -82,6 +82,10 @@ properties:
> >      type: boolean
> >      description: let the driver enable audio HDMI codec function or not.
> >
> > +  no-shift-audio-data:
> > +    type: boolean
> > +    description: Disable the first audio data bit shift in the TDM settings.
>
> This just looks like software policy, since there's no mention in the
> commit message or description as to what property of the hardware causes
> this to be required. Can you please explain why this property is needed?
>
> You're also missing a vendor prefix.
>
> Thanks,
> Conor.
>
> > +
> >    aux-bus:
> >      $ref: /schemas/display/dp-aux-bus.yaml#
> >
> >
> > --
> > 2.45.0.rc1.225.g2a3ae87e7f-goog
> >

Sorry, I found this feature in the datasheet originally, but after
deeper investigation, it seems that this feature should be used to
support i2s dsp mode b instead of being used this way. Note that the
difference between i2s dsp mode a and b is whether or not to shift the
audio data by 1 clock cycle.

Regards,
Hsin-Te