linux-kernel - Re: [TEGRA194_CPUFREQ PATCH v4 1/4] dt-bindings: arm: Add t194 ccplex compatible and bpmp property

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Date:   Fri, 26 Jun 2020 18:04:19 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     rjw@...ysocki.net, viresh.kumar@...aro.org,
        catalin.marinas@....com, will@...nel.org, thierry.reding@...il.com,
        robh+dt@...nel.org, devicetree@...r.kernel.org,
        jonathanh@...dia.com, talho@...dia.com, linux-pm@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, bbasu@...dia.com,
        mperttunen@...dia.com
Subject: Re: [TEGRA194_CPUFREQ PATCH v4 1/4] dt-bindings: arm: Add t194
 ccplex compatible and bpmp property

On Fri, Jun 26, 2020 at 09:13:53PM +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.
> 
> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> ---
>  Documentation/devicetree/bindings/arm/cpus.yaml | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
> index a018147..737b55e 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
>        - qcom,krait
>        - qcom,kryo
>        - qcom,kryo260
> @@ -255,6 +256,14 @@ properties:
>  
>        where voltage is in V, frequency is in MHz.
>  
> +  nvidia,bpmp:
> +    $ref: '/schemas/types.yaml#/definitions/phandle'
> +    descrption: |
> +      Specifies the bpmp node that needs to be queried to get
> +      operating point data for all CPUs.
> +
> +      Optional for NVIDIA Tegra194 Carmel CPUs

Hi,

The code (next patches) suggests, that the property is relevant for Tegra194
only. If it is required for compatible=tegra194-ccplex, then maybe you can
mark it so (there is already similar constraint described in the file, just
before the example section).

Best Regards,
Michał Mirosław