linux-kernel - Re: [PATCH 08/16] arm64: dts: allwinner: h6: Add HDMI audio node

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Message-ID: <4073007.RJdR9ZcIkj@jernej-laptop>
Date:   Wed, 08 Jul 2020 18:17:57 +0200
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     Clément Péron <peron.clem@...il.com>,
        Maxime Ripard <maxime@...no.tech>
Cc:     Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Marcus Cooper <codekipper@...il.com>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH 08/16] arm64: dts: allwinner: h6: Add HDMI audio node

Hi!

Dne ponedeljek, 06. julij 2020 ob 07:29:37 CEST je Maxime Ripard napisal(a):
> Hi,
> 
> On Sat, Jul 04, 2020 at 01:38:54PM +0200, Clément Péron wrote:
> > From: Jernej Skrabec <jernej.skrabec@...l.net>
> > 
> > Add a simple-soundcard to link audio between HDMI and I2S.
> > 
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> > Signed-off-by: Marcus Cooper <codekipper@...il.com>
> > Signed-off-by: Clément Péron <peron.clem@...il.com>
> > ---
> > 
> >  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 33 ++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> > b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi index
> > 78b1361dfbb9..ae169d07b939 100644
> > --- a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> > +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> > @@ -67,6 +67,25 @@ de: display-engine {
> > 
> >  		status = "disabled";
> >  	
> >  	};
> > 
> > +	hdmi_sound: hdmi-sound {
> > +		compatible = "simple-audio-card";
> > +		simple-audio-card,format = "i2s";
> > +		simple-audio-card,name = "sun50i-h6-hdmi";
> > +		simple-audio-card,mclk-fs = <128>;
> > +		simple-audio-card,frame-inversion;
> 
> Have you figured that one out?
> 
> > +		status = "disabled";
> > +
> > +		simple-audio-card,codec {
> > +			sound-dai = <&hdmi>;
> > +		};
> > +
> > +		simple-audio-card,cpu {
> > +			sound-dai = <&i2s1>;
> > +			dai-tdm-slot-num = <2>;
> > +			dai-tdm-slot-width = <32>;
> 
> I'm not sure why you need to use the TDM stuff here. IIRC the HDMI
> controller can output on up to 6 channels, so how would that work out?

dai-tdm-slot-width is needed to override automatic slot width selection. It 
should always be 32 for HDMI, no matter what is actual physical sample width. 
In this case this property is abused to set width also for I2S mode of 
operation. IMO there is no sense to duplicate code because I2S variant would 
work exactly the same, except name would be different.

I'm not sure about dai-tdm-slot-num. Marcus, can you explain the need for this 
property?

Would it be better to implement separate link driver instead of using simple-
card to hide all this properties into the code?

Best regards,
Jernej