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

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Message-ID: <YrfQXM7N/dn9odKL@builder.lan>
Date:   Sat, 25 Jun 2022 22:19:56 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Rajendra Nayak <quic_rjendra@...cinc.com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 Wed 22 Jun 06:58 CDT 2022, Rajendra Nayak wrote:

> 
> 
> On 6/7/2022 12:20 PM, Krzysztof Kozlowski wrote:
> > 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")
> 
> it seems pretty useful to have the "qcom,bwmon-v4" and "qcom,bwmon-v5"
> compatibles, I tried these patches on a sc7280 device which has a bwmon4
> between the cpu and caches (and also has a bwmon5 between the caches and DDR)
> and the driver works with zero changes.
> 

But does the '4' and '5' has a relation to the hardware? Or is just the
4th and 5th register layout supported by the downstream driver?

Regards,
Bjorn