linux-kernel - Re: [TEGRA194_CPUFREQ PATCH v5 1/4] dt-bindings: arm: Add t194 ccplex compatible and bpmp property

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Message-ID: <CAL_JsqL1CuumdT1CZiofEZw9j+3gsir8JwSrZVfcxFxEB=bavQ@mail.gmail.com>
Date:   Tue, 14 Jul 2020 07:46:11 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        devicetree@...r.kernel.org, Jon Hunter <jonathanh@...dia.com>,
        Timo Alho <talho@...dia.com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        bbasu@...dia.com, Mikko Perttunen <mperttunen@...dia.com>
Subject: Re: [TEGRA194_CPUFREQ PATCH v5 1/4] dt-bindings: arm: Add t194 ccplex
 compatible and bpmp property

On Tue, Jul 14, 2020 at 5:44 AM Sumit Gupta <sumitg@...dia.com> wrote:
>
>
>
> > On Mon, Jul 13, 2020 at 07:36:46PM +0530, Sumit Gupta wrote:
> >> To do frequency scaling on all CPUs within T194 CPU Complex, we need
> >> to query BPMP for data on valid operating points. Document a compatible
> >> string under 'cpus' node to represent the CPU Complex for binding drivers
> >> like cpufreq which don't have their node or CPU Complex node to bind to.
> >> Also, document a property to point to the BPMP device that can be queried
> >> for all CPUs.
> >
> > The cpus.yaml binding documents what's in 'cpu' nodes, not 'cpus'
> > node. AIUI, the latter is what you want. You should do your own schema
> > file here.
> >
> Do you mean to change existing file name from 'cpus.yaml' to 'cpu.yaml'
> and create new 'cpus.yaml' file?
> I think it's better to incorporate the change in existing 'cpus.yaml'
> file to keep both cpu@X and cpus node details together. Please suggest.

No, I'm suggesting you create nvidia,tegra194-ccplex.yaml.


> >> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> >> ---
> >>   Documentation/devicetree/bindings/arm/cpus.yaml | 11 +++++++++++
> >>   1 file changed, 11 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
> >> index a018147..9b328e3 100644
> >> --- a/Documentation/devicetree/bindings/arm/cpus.yaml
> >> +++ b/Documentation/devicetree/bindings/arm/cpus.yaml
> >> @@ -162,6 +162,7 @@ properties:
> >>         - nvidia,tegra132-denver
> >>         - nvidia,tegra186-denver
> >>         - nvidia,tegra194-carmel
> >> +      - nvidia,tegra194-ccplex
> >
> > Tegra194 has 2 different CPUs?
> >
> No, T194 SOC has homogeneous architecture with four clusters where each
> cluster has two symmetric cores. 'nvidia,tegra194-carmel' compatible
> string represents each cpu. 'nvidia,tegra194-ccplex' string represents
> the CPU Complex to bind cpufreq driver. The change was done as per
> discussion [1]

You are adding the compatible string to the cpu@N node compatible.

>
> >>         - qcom,krait
> >>         - qcom,kryo
> >>         - qcom,kryo260
> >> @@ -255,6 +256,15 @@ properties:
> >>
> >>         where voltage is in V, frequency is in MHz.
> >>
> >> +  nvidia,bpmp:
> >> +    $ref: '/schemas/types.yaml#/definitions/phandle'
> >> +    description: |
> >> +      Specifies the bpmp node that needs to be queried to get
> >> +      operating point data for all CPUs.
> >> +
> >> +      Optional for systems that have a "compatible"
> >> +      property value of "nvidia,tegra194-ccplex".
> >> +
> >>     power-domains:
> >>       $ref: '/schemas/types.yaml#/definitions/phandle-array'
> >>       description:
> >> @@ -340,6 +350,7 @@ required:
> >>
> >>   dependencies:
> >>     rockchip,pmu: [enable-method]
> >> +  nvidia,bpmp: [compatible]
> >>
> >>   examples:
> >>     - |
> >> --
> >> 2.7.4
> >>
>
> [1] https://marc.info/?l=linux-arm-kernel&m=158999171528418&w=2