linux-kernel - Re: [PATCH v4 09/22] arm64: dts: allwinner: h6: Add HDMI audio node

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Message-ID: <20201102102117.hp6v5nnkhzp3bful@gilmour.lan>
Date:   Mon, 2 Nov 2020 11:21:17 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Jernej Škrabec <jernej.skrabec@...l.net>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Marcus Cooper <codekipper@...il.com>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v4 09/22] arm64: dts: allwinner: h6: Add HDMI audio node

On Sun, Nov 01, 2020 at 04:27:05PM +0100, Clément Péron wrote:
> On Wed, 30 Sep 2020 at 12:19, Maxime Ripard <maxime@...no.tech> wrote:
> >
> > On Mon, Sep 28, 2020 at 04:27:42PM +0200, Clément Péron wrote:
> > > On Mon, 28 Sep 2020 at 10:43, Maxime Ripard <maxime@...no.tech> wrote:
> > > >
> > > > On Mon, Sep 21, 2020 at 08:37:09PM +0200, Jernej Škrabec wrote:
> > > > > Dne ponedeljek, 21. september 2020 ob 19:23:49 CEST je Clément Péron
> > > > > napisal(a):
> > > > > > Hi Maxime,
> > > > > >
> > > > > > On Mon, 21 Sep 2020 at 15:59, Maxime Ripard <maxime@...no.tech> wrote:
> > > > > > >
> > > > > > > On Mon, Sep 21, 2020 at 12:27:18PM +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 28c77d6872f6..a8853ee7885a 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;
> > > > > > > > +             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>;
> > > > > > >
> > > > > > > It looks weird to have both some TDM setup here, and yet the format in
> > > > > > > i2s?
> 
> 
> I was looking at sound documentation regarding how I can properly
> write the multi-lane I2S support.
> And I think we made a wrong interpretation here.
> 
> TDM slot-num and slot-width are not referencing the format called PCM
> or DSP_A / DSP_B.
> But really the physical time division representation of a format.
> 
> For example Amlogic do the following representation for Multi-lane I2S:
> 
> dai-link-7 {
>     sound-dai = <&tdmif_b>;
>     dai-format = "i2s";
>     dai-tdm-slot-tx-mask-0 = <1 1>;
>     dai-tdm-slot-tx-mask-1 = <1 1>;
>     dai-tdm-slot-tx-mask-2 = <1 1>;
>     dai-tdm-slot-tx-mask-3 = <1 1>;
>     mclk-fs = <256>;
> 
>     codec {
>         sound-dai = <&tohdmitx TOHDMITX_I2S_IN_B>;
>     };
> };
> 
> So i think for 2 channels HDMI using the simple sound card with TDM
> property is not a hack but the correct way to represent it.
> 
> Do you agree ?
> 
> If so, can I resend the simple sound card for HDMI audio ?

I mean, it's not less weird :)

And like I said before we still have the option to write a card driver
ourselves that doesn't take anything from the DT beside the phandle of
the i2s controller and the HDMI controller.

If it's a fixed configuration, I'm not sure why we bother trying to make
it dynamic in the DT.

Maxime

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