linux-kernel - Re: [PATCH v4 2/2] arm64: dts: qcom: Add sound node for sc7180-trogdor-coachz

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Message-ID: <CAD=FV=VZrfgZHXBFKD2f8uygQC32mPt1CQqMpUzio+yq_Era0A@mail.gmail.com>
Date:   Thu, 11 Mar 2021 11:54:03 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Srinivasa Rao Mandadapu <srivasam@...eaurora.org>
Cc:     gross@...nel.org, Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Rohit kumar <rohitkr@...eaurora.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Judy Hsiao <judyhsiao@...omium.org>
Subject: Re: [PATCH v4 2/2] arm64: dts: qcom: Add sound node for sc7180-trogdor-coachz

Hi,

On Thu, Mar 11, 2021 at 8:48 AM Srinivasa Rao Mandadapu
<srivasam@...eaurora.org> wrote:
>
> This is a trgodor variant, required to have sound node variable
> for coachz specific platform.
>
> Signed-off-by: Srinivasa Rao Mandadapu <srivasam@...eaurora.org>
> ---
>  .../boot/dts/qcom/sc7180-trogdor-coachz.dtsi   | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor-coachz.dtsi b/arch/arm64/boot/dts/qcom/sc7180-trogdor-coachz.dtsi
> index 4ad520f00485..7623a30a64c7 100644
> --- a/arch/arm64/boot/dts/qcom/sc7180-trogdor-coachz.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor-coachz.dtsi
> @@ -238,3 +238,21 @@ &tlmm {
>                           "DP_HOT_PLUG_DET",
>                           "EC_IN_RW_ODL";
>  };
> +
> +&sound {
> +       compatible = "google,sc7180-coachz";

You're placing this in the wrong place. Pay attention to the section
headings. Your patch is putting this in the section "PINCTRL -
board-specific pinctrl". That's not right.


> +       model = "sc7180-adau7002-max98357a";
> +       audio-routing = "PDM_DAT", "DMIC";
> +
> +       dai-link@0 {
> +               link-name = "MultiMedia0";
> +               reg = <0>;
> +               cpu {
> +                       sound-dai = <&lpass_cpu 0>;

Shouldn't the 0 above be "MI2S_PRIMARY" ?  ...and the "reg" as well?


> +               };
> +
> +               codec {
> +                       sound-dai = <&adau7002>;
> +               };
> +       };

Some overall notes, though:

1. You don't actually need to duplicate everything that you have
above. Whether you realize it or not the way devicetree works is that
it _merges_ the node in the "coachz" devicetree with the one from the
trogdor one (it doesn't replace it). So in trogdor you have:

dai-link@0 {
  link-name = "MultiMedia0";
  reg = <MI2S_PRIMARY>;
  cpu {
    sound-dai = <&lpass_cpu MI2S_PRIMARY>;
  };

  codec {
    sound-dai = <&alc5682 MI2S_PRIMARY>;
  };
};

...and in coachz you have:

dai-link@0 {
  link-name = "MultiMedia0";
  reg = <MI2S_PRIMARY>;
  cpu {
    sound-dai = <&lpass_cpu MI2S_PRIMARY>;
  };

  codec {
    sound-dai = <&adau7002>;
  };
};

Almost all of that is duplication. It's best not to duplicate. Thus,
one step better than what you have would be to just have this in
coachz to override what you need:

dai-link@0 {
  codec {
    sound-dai = <&adau7002>;
  };
};


2. In general it's discouraged (and error prone) to try to replicate
hierarchies from your parent. So the best would be to change trogdor's
device tree to something like this:

dai-link@0 {
  link-name = "MultiMedia0";
  reg = <MI2S_PRIMARY>;
  cpu {
    sound-dai = <&lpass_cpu MI2S_PRIMARY>;
  };

  multimedia0_codec: codec {
    sound-dai = <&alc5682 MI2S_PRIMARY>;
  };
};

...and then in coachz you override like:

&multimedia0_codec {
   sound-dai = <&alc5682 MI2S_PRIMARY>;
};