Re: [TEGRA194_CPUFREQ Patch v3 1/4] dt-bindings: arm: Add t194 ccplex compatible and bpmp property

[Sumit Gupta]

On 22/06/20 12:52 PM, Viresh Kumar wrote:
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>
> On 22-06-20, 03:04, 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.
>
> You shouldn't be putting how linux is going to use this information and entries
> shouldn't be made just so cpufreq can bind to a driver.
>
> Though I see that this is a real hardware register which you can use to interact
> with the firmware ? And so it makes sense to have it, maybe in different form
> though.
CPUFREQ driver doesn't communicate directly with BPMP firmware. It uses 
BPMP node's reference to call api's exported by BPMP driver which 
communicates with BPMP firmware.

> I will let Rob explain what would be the right way of doing this though.
This is already discussed by Thierry with Rob.
Please refer https://marc.info/?l=linux-arm-kernel&m=158999171528418&w=2

> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   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
> > +
> >     power-domains:
> >       $ref: '/schemas/types.yaml#/definitions/phandle-array'
> >       description:
> > --
> > 2.7.4
>
> --
> viresh