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Subject: Re: [PATCH v4 2/2] arm64: dts: qcom: Add sound node for
 sc7180-trogdor-coachz
To:     Doug Anderson <dianders@chromium.org>
Cc:     gross@kernel.org, Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Rohit kumar <rohitkr@codeaurora.org>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Judy Hsiao <judyhsiao@chromium.org>
References: <20210311164815.14113-1-srivasam@codeaurora.org>
 <20210311164815.14113-3-srivasam@codeaurora.org>
 <CAD=FV=VZrfgZHXBFKD2f8uygQC32mPt1CQqMpUzio+yq_Era0A@mail.gmail.com>
From:   Srinivasa Rao Mandadapu <srivasam@codeaurora.org>
Organization: Qualcomm India Private Limited.
Message-ID: <ac6695e0-0628-4b05-bb55-db5abb577158@codeaurora.org>
Date:   Fri, 12 Mar 2021 21:23:45 +0530
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Hi Doug,

Thanks for time and valuable inputs!!!

On 3/12/2021 1:24 AM, Doug Anderson wrote:
> Hi,
>
> On Thu, Mar 11, 2021 at 8:48 AM Srinivasa Rao Mandadapu
> <srivasam@codeaurora.org> wrote:
>> This is a trgodor variant, required to have sound node variable
>> for coachz specific platform.
>>
>> Signed-off-by: Srinivasa Rao Mandadapu <srivasam@codeaurora.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?
Yes, It's required. Will change, and re-post.
>
>
>> +               };
>> +
>> +               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>;
> };
Okay. Will change accordingly and re-post.

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