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Date:   Thu, 30 Jun 2022 16:44:27 +0530
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Subject: Re: [PATCH v6 1/4] dt-bindings: interconnect: qcom,msm8998-cpu-bwmon:
 add BWMON device
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To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        "Georgi Djakov" <djakov@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <linux-pm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>
CC:     Rob Herring <robh@kernel.org>
References: <20220629140302.236715-1-krzysztof.kozlowski@linaro.org>
 <20220629140302.236715-2-krzysztof.kozlowski@linaro.org>
From:   Rajendra Nayak <quic_rjendra@quicinc.com>
In-Reply-To: <20220629140302.236715-2-krzysztof.kozlowski@linaro.org>
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On 6/29/2022 7:32 PM, Krzysztof Kozlowski wrote:
> Add bindings for the Qualcomm Bandwidth Monitor device providing
> performance data on interconnects.  The bindings describe only BWMON CPU
> (version 4), e.g. the instance which appeared for the first on Qualcomm
> MSM8998 SoC and is also used on SDM845.  This BWMON device sits between
> CPU and Last Level Cache Controller.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Reviewed-by: Rob Herring <robh@kernel.org>
> Acked-by: Georgi Djakov <djakov@kernel.org>
> ---
>   .../interconnect/qcom,msm8998-llcc-bwmon.yaml | 85 +++++++++++++++++++
>   1 file changed, 85 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/interconnect/qcom,msm8998-llcc-bwmon.yaml
> 
> diff --git a/Documentation/devicetree/bindings/interconnect/qcom,msm8998-llcc-bwmon.yaml b/Documentation/devicetree/bindings/interconnect/qcom,msm8998-llcc-bwmon.yaml
> new file mode 100644
> index 000000000000..76e09658d615
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/interconnect/qcom,msm8998-llcc-bwmon.yaml
> @@ -0,0 +1,85 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/interconnect/qcom,msm8998-llcc-bwmon.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm Interconnect Bandwidth Monitor
> +
> +maintainers:
> +  - Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> +
> +description: |
> +  Bandwidth Monitor measures current throughput on buses between various NoC
> +  fabrics and provides information when it crosses configured thresholds.
> +
> +  Certain SoCs might have more than one Bandwidth Monitors, for example on SDM845::
> +   - Measuring the bandwidth between CPUs and Last Level Cache Controller -
> +     called LLCC BWMON,
> +   - Measuring the bandwidth between Last Level Cache Controller and memory (DDR).
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - enum:
> +              - qcom,sdm845-llcc-bwmon
> +          - const: qcom,msm8998-llcc-bwmon
> +      - const: qcom,msm8998-llcc-bwmon       # BWMON v4
> +
> +  interconnects:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  operating-points-v2: true
> +  opp-table: true
> +
> +  reg:
> +    # BWMON v4 (currently described) and BWMON v5 use one register address
> +    # space.  BWMON v2 uses two register spaces - not yet described.
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - interconnects
> +  - interrupts
> +  - operating-points-v2
> +  - opp-table
> +  - reg
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interconnect/qcom,sdm845.h>
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +
> +    pmu@1436400 {
> +        compatible = "qcom,sdm845-llcc-bwmon", "qcom,msm8998-llcc-bwmon";

so with this compatible fallback scheme, I am trying to understand what
do I need to do if I have to add support for another SoC for instance.

I just update the binding with the new SoC compatible (lets say qcom,sc7280-llcc-bwmon)
and in the device tree node use it as
	compatible = "qcom,sc7280-llcc-bwmon", "qcom,sdm845-llcc-bwmon", "qcom,msm8998-llcc-bwmon";
without any updates in the driver?

> +        reg = <0x01436400 0x600>;
> +        interrupts = <GIC_SPI 581 IRQ_TYPE_LEVEL_HIGH>;
> +        interconnects = <&gladiator_noc MASTER_APPSS_PROC 3 &mem_noc SLAVE_LLCC 3>;
> +
> +        operating-points-v2 = <&llcc_bwmon_opp_table>;
> +
> +        llcc_bwmon_opp_table: opp-table {
> +            compatible = "operating-points-v2";
> +            opp-0 {
> +                opp-peak-kBps = <4800000>;
> +            };
> +            opp-1 {
> +                opp-peak-kBps = <9216000>;
> +            };
> +            opp-2 {
> +                opp-peak-kBps = <15052800>;
> +            };
> +            opp-3 {
> +                opp-peak-kBps = <20889600>;
> +            };
> +            opp-4 {
> +                opp-peak-kBps = <25497600>;
> +            };
> +        };
> +    };