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

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Date:   Sun, 1 Nov 2020 16:27:05 +0100
From:   Clément Péron <peron.clem@...il.com>
To:     Maxime Ripard <maxime@...no.tech>, Mark Brown <broonie@...nel.org>
Cc:     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

Hi Maxime,


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 ?

Thanks,
Clement

> > > > >
> > > > > Yes, I agree I will check if it's really needed.
> > > >
> > > > I think this was explained before.
> > >
> > > Possibly, but this should be in a comment or at least the commit log
> > >
> > > > Anyway, this is needed to force width to 32, no matter actual sample
> > > > width. That's a requirement of HDMI codec. I believe Marcus Cooper
> > > > have another codec which also needs fixed width.
> > > >
> > > > There is no similar property for I2S, so TDM one is used here.
> > >
> > > Except it's really dedicated to the TDM mode and doesn't really make
> > > much sense here.
> > >
> > > If we have special requirements like this on the codec setup, that
> > > sounds like a good justification for creating a custom codec instead of
> > > shoehorning it into simple-card
> >
> > When all the remarks are fixed would it be possible to merge the rest
> > of the series without the dts changes ?
> >
> > I will propose another series to introduce a dedicated codec for that.
>
> Yeah, sure
>
> Maxime