linux-kernel - Re: [PATCH v2 2/6] dt-bindings: interconnect: Add property to set BCM TCS wait behavior

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Date:   Fri, 17 Jul 2020 17:41:01 -0700
From:   Mike Tipton <mdtipton@...eaurora.org>
To:     Rob Herring <robh@...nel.org>
Cc:     georgi.djakov@...aro.org, bjorn.andersson@...aro.org,
        agross@...nel.org, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/6] dt-bindings: interconnect: Add property to set BCM
 TCS wait behavior

On 7/10/2020 9:31 AM, Rob Herring wrote:
> On Thu, Jul 09, 2020 at 06:56:48PM -0700, Mike Tipton wrote:
>> Add "qcom,tcs-wait" property to set which TCS should wait for completion
>> when triggering.
>>
>> Signed-off-by: Mike Tipton <mdtipton@...eaurora.org>
>> ---
>>   .../bindings/interconnect/qcom,bcm-voter.yaml       | 13 +++++++++++++
>>   1 file changed, 13 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/interconnect/qcom,bcm-voter.yaml b/Documentation/devicetree/bindings/interconnect/qcom,bcm-voter.yaml
>> index 5971fc1df08d..f0c3d6b01831 100644
>> --- a/Documentation/devicetree/bindings/interconnect/qcom,bcm-voter.yaml
>> +++ b/Documentation/devicetree/bindings/interconnect/qcom,bcm-voter.yaml
>> @@ -21,6 +21,16 @@ properties:
>>       enum:
>>         - qcom,bcm-voter
>>   
>> +  qcom,tcs-wait:
>> +    description: |
>> +      Optional mask of which TCSs (Triggered Command Sets) wait for completion
>> +      upon triggering. In most cases, it's necessary to wait in both the AMC
>> +      and WAKE sets to ensure resources are available before use. If a specific
>> +      RSC and its use cases can ensure sufficient delay by other means, then
>> +      this can be overridden to reduce latencies.
> 
> I have no idea what any of this means to provide any meaningful comment.
> 
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    default: QCOM_ICC_TAG_ACTIVE_ONLY
> 
> Can't use defines here.

What's the recommended alternative? The meaning isn't obvious as a raw 
number (3). We expect the defines to be used in the dt files themselves 
(see example below). Is this just a restriction for the `default` 
documentation specifically? I could just mention the default behavior in 
the description I suppose, but that seems to defeat the purpose of 
having a separate `default` key.

> 
>> +
>>   required:
>>     - compatible
>>   
>> @@ -39,7 +49,10 @@ examples:
>>     # as defined in Documentation/devicetree/bindings/soc/qcom/rpmh-rsc.txt
>>     - |
>>   
>> +    #include <dt-bindings/interconnect/qcom,icc.h>
>> +
>>       disp_bcm_voter: bcm_voter {
>>           compatible = "qcom,bcm-voter";
>> +        qcom,tcs-wait = <QCOM_ICC_TAG_AMC>;
>>       };
>>   ...
>> -- 
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> a Linux Foundation Collaborative Project
>>