linux-kernel - Re: [PATCH v4 1/4] dt-bindings: interconnect: qcom,sdm845-cpu-bwmon: add BWMON device

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Message-ID: <3e4e504c-5a38-43cd-ea8d-afbbb72eacad@linaro.org>
Date:   Tue, 7 Jun 2022 08:50:49 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Andy Gross <agross@...nel.org>, Georgi Djakov <djakov@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v4 1/4] dt-bindings: interconnect: qcom,sdm845-cpu-bwmon:
 add BWMON device

On 06/06/2022 23:11, Bjorn Andersson wrote:
> On Wed 01 Jun 03:11 PDT 2022, Krzysztof Kozlowski wrote:
> 
>> Add bindings for the Qualcomm Bandwidth Monitor device providing
>> performance data on interconnects.  The bindings describe only BWMON
>> version 4, e.g. the instance on SDM845 between CPU and Last Level Cache
>> Controller.
>>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Reviewed-by: Rob Herring <robh@...nel.org>
>> Acked-by: Georgi Djakov <djakov@...nel.org>
>> ---
>>  .../interconnect/qcom,sdm845-cpu-bwmon.yaml   | 97 +++++++++++++++++++
>>  1 file changed, 97 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml b/Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml
>> new file mode 100644
>> index 000000000000..8c82e06ee432
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml
>> @@ -0,0 +1,97 @@
>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/interconnect/qcom,sdm845-cpu-bwmon.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Qualcomm Interconnect Bandwidth Monitor
>> +
>> +maintainers:
>> +  - Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> +
>> +description:
>> +  Bandwidth Monitor measures current throughput on buses between various NoC
>> +  fabrics and provides information when it crosses configured thresholds.
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - qcom,sdm845-cpu-bwmon       # BWMON v4
> 
> It seems the thing that's called bwmon v4 is compatible with a number of
> different platforms, should we add a generic compatible to the binding
> as well, to avoid having to update the implementation for each SoC?
> 
> (I.e. "qcom,sdm845-cpu-bwmon", "qcom,bwmon-v4")

I am hesitant. I could not find BWMON IP block versioning in the
Qualcomm docs. Only the downstream sources had it. Therefore I think it
is more applicable to use this one as fallback for other boards, e.g.:

"qcom,sdm660-cpu-bwmon", "qcom,sdm845-cpu-bwmon"
(even if the number is a bit odd - newer comes as last compatible).

What's your preference?

Best regards,
Krzysztof