linux-kernel - Re: [PATCH v1 3/3] dt-bindings: ASoC: Add ESS ES9218P codec bindings

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Message-ID: <7Zga7RBqLNcaG5ylTIY4Qn7CUdE1IJsW@localhost>
Date:   Thu, 11 May 2023 11:15:38 +0100
From:   Aidan MacDonald <aidanmacdonald.0x0@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     lgirdwood@...il.com, broonie@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        perex@...ex.cz, tiwai@...e.com, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/3] dt-bindings: ASoC: Add ESS ES9218P codec bindings


Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> writes:

> On 10/05/2023 13:23, Aidan MacDonald wrote:
>> ...
>> +  ess,max-clock-div:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description:
>> +      Sets the maximum MCLK divider for generating the internal CLK.
>> +      CLK must be at least 20x the I2C bus speed or I2C transactions
>> +      will fail. The maximum divider should be chosen to ensure that
>> +      CLK will not fall below the limit.
>> +    enum:
>> +      - 1
>> +      - 2
>> +      - 4
>> +      - 8
>> +    default: 1
>
> Why do you need to customize it per board?
>

There's no generic API to read or change the bus speed (SCL frequency)
for I2C adapters, so it's impossible to calculate a limit on the MCLK
divider automatically.

Defaulting to 1 is always safe, but means wasting power at lower sample
rates. If you know what the bus speed is you can use a higher divider
limit to save power, and it has to be done at the board/firmware level
because that's the only place where the bus speed is known.

>> +
>> +  ess,oscillator-pad-bias:
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    description: Sets the oscillator pad drive bias. 0 - full bias, 15 - disabled.
>> +    minimum: 0
>> +    maximum: 15
>> +    default: 0
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - "#sound-dai-cells"
>> +  - avdd-supply
>> +  - vcca-supply
>> +  - avcc3v3-supply
>> +  - avcc1v8-supply
>> +  - clocks
>> +  - clock-names
>> +  - reset-gpios
>> +
>> +additionalProperties: false
>
> Instead: unevaluatedProperties: false
>
>
>> +
>> +examples:
>
> Best regards,
> Krzysztof

Everything else agreed, I'll send v2 later today.

Regards,
Aidan