linux-kernel - Re: [PATCH v2 1/9] dt-bindings: arm: Add support for DSB element

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Message-ID: <3c3c55a8-8979-76f9-3b61-31c50ceefd33@arm.com>
Date:   Mon, 27 Feb 2023 10:44:28 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Tao Zhang <quic_taozha@...cinc.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Jinlong Mao <quic_jinlmao@...cinc.com>,
        Leo Yan <leo.yan@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>,
        linux-arm-msm@...r.kernel.org, bjorn.andersson@...aro.org,
        Tao Zhang <taozha@....qualcomm.com>
Subject: Re: [PATCH v2 1/9] dt-bindings: arm: Add support for DSB element

On 27/02/2023 03:07, Tao Zhang wrote:
> Hi Suzuki,
> 
> 在 2/22/2023 2:11 AM, Suzuki K Poulose 写道:
>> On 19/01/2023 07:41, Tao Zhang wrote:
>>> Add property "qcom,dsb-elem-size" to support DSB(Discrete Single
>>> Bit) element for TPDA. Specifies the DSB element size supported
>>> by each monitor connected to the aggregator on each port. Should
>>> be specified in pairs (port, dsb element size).
>>>
>>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>>> Signed-off-by: Tao Zhang <taozha@....qualcomm.com>
>>> ---
>>>   .../bindings/arm/qcom,coresight-tpda.yaml          | 22 
>>> ++++++++++++++++++++++
>>>   1 file changed, 22 insertions(+)
>>>
>>> diff --git 
>>> a/Documentation/devicetree/bindings/arm/qcom,coresight-tpda.yaml 
>>> b/Documentation/devicetree/bindings/arm/qcom,coresight-tpda.yaml
>>> index 2ec9b5b..298db7f 100644
>>> --- a/Documentation/devicetree/bindings/arm/qcom,coresight-tpda.yaml
>>> +++ b/Documentation/devicetree/bindings/arm/qcom,coresight-tpda.yaml
>>> @@ -58,6 +58,26 @@ properties:
>>>       minItems: 1
>>>       maxItems: 2
>>>   +  qcom,dsb-element-size:
>>> +    description: |
>>> +      Specifies the DSB(Discrete Single Bit) element size supported by
>>> +      each monitor connected to the aggregator on each port. Should be
>>> +      specified in pairs <port, dsb element size>.
>>
>> Isn't this a property of the TPDM connected to the port ? i.e. the DSB 
>> size ? Thus shouldn't this be part of the TPDM device (and the TPDA 
>> will be able to find it from the TPDM device) ?
>>
> Since  the port number is about the input port of TPDA, this property 
> needs to be configured in the TPDA-related settings.

That is because, you chose to describe the property of TPDM in TPDA ?
Instead if you do it as follows :

  tpdm {
        qcom,tpdm-dsb-elemenet-size = <32>
        out_ports {

	port {
              remote-endpoint=<&tpda_port_number>;
	}
  }

  tpda {
        in_ports {
            port {
                  remote-endpoint=<&tpdm0_port0>;
            }
        }
  }


The TPDA driver can figure out the "port" that a given TPDM is connected
to and thus find out the DSB size. For the tpda driver, pdata->conns
could hold the reference to the TPDM device and thus fetch the DSB size.
(Note: James is working on a patch to add input port connections to the
platform data).

Suzuki