linux-kernel - Re: [PATCH v2 2/7] dt-bindings: soundwire: qcom: add 16-bit sample interval

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Message-ID: <9156affd-7f08-282b-ee65-ae82f4d94cbc@linaro.org>
Date:   Thu, 13 Apr 2023 12:12:19 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Rao Mandadapu <quic_srivasam@...cinc.com>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, alsa-devel@...a-project.org
Cc:     Patrick Lai <quic_plai@...cinc.com>
Subject: Re: [PATCH v2 2/7] dt-bindings: soundwire: qcom: add 16-bit sample
 interval



On 12/04/2023 17:16, Krzysztof Kozlowski wrote:
> On 12/04/2023 17:28, Srinivas Kandagatla wrote:
>>
>>
>> On 03/04/2023 14:24, Krzysztof Kozlowski wrote:
>>> The port sample interval was always 16-bit, split into low and high
>>> bytes.  This split was unnecessary, although harmless for older devices
>>> because all of them used only lower byte (so values < 0xff).  With
>>> support for Soundwire controller on Qualcomm SM8550 and its devices,
>>> both bytes will be used, thus add a new 'qcom,ports-sinterval' property
>>> to allow 16-bit sample intervals.
>>>
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>> ---
>>>    .../bindings/soundwire/qcom,soundwire.yaml    | 22 +++++++++++++++++--
>>>    1 file changed, 20 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/soundwire/qcom,soundwire.yaml b/Documentation/devicetree/bindings/soundwire/qcom,soundwire.yaml
>>> index c283c594fb5c..883b8be9be1b 100644
>>> --- a/Documentation/devicetree/bindings/soundwire/qcom,soundwire.yaml
>>> +++ b/Documentation/devicetree/bindings/soundwire/qcom,soundwire.yaml
>>> @@ -86,7 +86,7 @@ properties:
>>>      qcom,ports-sinterval-low:
>>>        $ref: /schemas/types.yaml#/definitions/uint8-array
>>>        description:
>>> -      Sample interval low of each data port.
>>> +      Sample interval (only lowest byte) of each data port.
>>>          Out ports followed by In ports. Used for Sample Interval calculation.
>>>          Value of 0xff indicates that this option is not implemented
>>>          or applicable for the respective data port.
>>> @@ -94,6 +94,19 @@ properties:
>>>        minItems: 3
>>>        maxItems: 16
>>>    
>>> +  qcom,ports-sinterval:
>>> +    $ref: /schemas/types.yaml#/definitions/uint32-array
>>
>> Should this not be ref: /schemas/types.yaml#/definitions/uint16-array ?
> 
> Same answer as for Rob:
> 
> Because I am afraid it will grow in next version to 24 or 32 bits. I can
> change easily maximum, but if I put here uint16-array, all DTS will have
> /bytes 16/ annotation.
> 
As per MiPi Specs the sample Interval is an integer in the range 2 to 
65535. I don't see a value in making this u32, other than adding some 
confusion by deviating from specs.

--srini

> Best regards,
> Krzysztof
>