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

[Sumit Gupta]

> 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.

> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   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]

> >         - 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