linux-kernel - Re: [PATCH v4 1/9] ASoC: dt-bindings: wcd938x: add bindings for wcd938x

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Date:   Thu, 15 Apr 2021 17:53:24 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     broonie@...nel.org, devicetree@...r.kernel.org, perex@...ex.cz,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        lgirdwood@...il.com
Subject: Re: [PATCH v4 1/9] ASoC: dt-bindings: wcd938x: add bindings for
 wcd938x

Thanks Rob for quick review,

On 15/04/2021 17:29, Rob Herring wrote:
> On Wed, Apr 14, 2021 at 04:48:37PM +0100, Srinivas Kandagatla wrote:
>> Qualcomm WCD9380/WCD9385 Codec is a standalone Hi-Fi audio codec IC
>> connected over SoundWire. This device has two SoundWire device RX and
>> TX respectively, supporting 4 x ADCs, ClassH, Ear, Aux PA, 2xHPH,
>> 7 x TX diff inputs, 8 DMICs, MBHC.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>   .../bindings/sound/qcom,wcd938x.yaml          | 176 ++++++++++++++++++
>>   1 file changed, 176 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/sound/qcom,wcd938x.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/sound/qcom,wcd938x.yaml b/Documentation/devicetree/bindings/sound/qcom,wcd938x.yaml
>> new file mode 100644
>> index 000000000000..4c8fa8290af0
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/sound/qcom,wcd938x.yaml
>> @@ -0,0 +1,176 @@

...

>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    codec {
>> +        compatible = "qcom,wcd9380-codec";
>> +        reset-gpios = <&tlmm 32 0>;
>> +        #sound-dai-cells = <1>;
>> +        qcom,tx-device = <&wcd938x_tx>;
>> +        qcom,rx-device = <&wcd938x_rx>;
>> +        qcom,micbias1-microvolt = <1800000>;
>> +        qcom,micbias2-microvolt = <1800000>;
>> +        qcom,micbias3-microvolt = <1800000>;
>> +        qcom,micbias4-microvolt = <1800000>;
>> +        qcom,mbhc-hphl-switch;
>> +        qcom,mbhc-ground-switch;
>> +        qcom,mbhc-button0-vthreshold-microvolt = <75000>;
>> +        qcom,mbhc-button1-vthreshold-microvolt = <150000>;
>> +        qcom,mbhc-button2-vthreshold-microvolt = <237000>;
>> +        qcom,mbhc-button3-vthreshold-microvolt = <500000>;
>> +        qcom,mbhc-button5-vthreshold-microvolt = <500000>;
>> +        qcom,mbhc-button6-vthreshold-microvolt = <500000>;
>> +        qcom,mbhc-button7-vthreshold-microvolt = <500000>;
>> +    };
>> +
>> +    /* ... */
>> +
>> +    soundwire@...0000 {
>> +        #address-cells = <2>;
>> +        #size-cells = <0>;
>> +        reg = <0x03230000 0x2000>;
>> +        wcd938x_tx: codec@0,3 {
>> +            compatible = "sdw20217010d00";
>> +            reg  = <0 3>;
>> +            qcom,direction = "tx";
>> +            qcom,port-mapping = <2 3 4 5>;
>> +        };
>> +
>> +        wcd938x_rx: codec@0,4 {
>> +            compatible = "sdw20217010d00";
>> +            reg  = <0 4>;
>> +            qcom,direction = "rx";
>> +            qcom,port-mapping = <1 2 3 4 5>;
>> +        };
> 
> This is a single device, right? We shouldn't need 3 nodes to describe
> it. I think this should all be a single node like this:
> 
No, WCD938x is a Audio Codec which has two SoundWire Slave device (TX 
and RX). WCD938X reset lines and supplies are common for both TX and RX 
SoundWire devices.

However TX SoundWire device only has register access to codec 
CSR(Control Status registers).

So there are two SoundWire devices and a WCD938X common parts. Now 
making the common Codec part as a separate device made more sense here.
So we ended with total 3 devices.

1 . WCD938x Codec which deals with all the codec side including Common 
parts.
2. TX SoundWire device to configure TX SoundWire ports/interface and 
provide CSR access.
3. RX SoundWire device to configure RX Soundwire ports/interface


> codec@0,3 {
>          reg = <0 3>, <0 4>;

We can't have this, as these two SoundWire devices hang on different 
SoundWire bus instances.

> 	compatible = "sdw20217010d00";
> 
>          reset-gpios = <&tlmm 32 0>;
>          #sound-dai-cells = <1>;
>          qcom,micbias1-microvolt = <1800000>;
>          qcom,micbias2-microvolt = <1800000>;
>          qcom,micbias3-microvolt = <1800000>;
>          qcom,micbias4-microvolt = <1800000>;
>          qcom,mbhc-hphl-switch;
>          qcom,mbhc-ground-switch;
>          qcom,mbhc-button0-vthreshold-microvolt = <75000>;
>          qcom,mbhc-button1-vthreshold-microvolt = <150000>;
>          qcom,mbhc-button2-vthreshold-microvolt = <237000>;
>          qcom,mbhc-button3-vthreshold-microvolt = <500000>;
>          qcom,mbhc-button5-vthreshold-microvolt = <500000>;
>          qcom,mbhc-button6-vthreshold-microvolt = <500000>;
>          qcom,mbhc-button7-vthreshold-microvolt = <500000>;
> };
> 
> You'll have to figure out the qcom,direction and qcom,port-mapping parts
> though.

That is the reason why we ended up with 3 devices here.

--srini
> 
> Rob
>