Re: [PATCH 2/4] dt-bindings: tegra: Document Jetson Orin Nano

[Thierry Reding <thierry.reding@gmail.com>]

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On Fri, Mar 31, 2023 at 10:20:16PM +0200, Krzysztof Kozlowski wrote:
> On 31/03/2023 18:31, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > The Jetson Orin Nano is the little sibling of the Jetson Orin NX.
> > Document the corresponding compatible strings for these devices.
> > 
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> >  Documentation/devicetree/bindings/arm/tegra.yaml | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/arm/tegra.yaml b/Documentation/devicetree/bindings/arm/tegra.yaml
> > index 61e638c9cad7..60c151da5e06 100644
> > --- a/Documentation/devicetree/bindings/arm/tegra.yaml
> > +++ b/Documentation/devicetree/bindings/arm/tegra.yaml
> > @@ -220,6 +220,13 @@ properties:
> >                - nvidia,p3767-0001
> >                - nvidia,p3767-0002
> >            - const: nvidia,tegra234
> > +      - description: Jetson Orin Nano
> > +        items:
> > +          - enum:
> > +              - nvidia,p3767-0003
> > +              - nvidia,p3767-0004
> > +              - nvidia,p3767-0005
> 
> Similar questions as for patch #1. Where are the DTSes? Where are the
> differences? If we keep documenting every SKU which is the same from
> user/OS perspective, this list would grow crazy.

Most of the differences will be user-noticeable, even if they can be
runtime detected. Besides the mentioned differences in DRAM size, things
like the number of CPUs, GPU compute units or video encoders/decoders
can vary depending on the SKU. While the OS should certainly be able to
abstract all of that away as best as possible, on user may still end up
with SKU 3 and another with SKU 5 and it's important for people to know
what they have.

So I think we have to find a way to both keep things simple from a DTS
point of view (as I said, we should be able to make do with one DTS file
for the Jetson Orin NX and one for the Jetson Orin Nano with UEFI taking
care of fixing up the DTS per SKU), and not lying to users. If users get
a SKU 3, then that's what we should report instead of 3 (or whatever
ends up being the SKU that we use in the DTS).

So I want to be as complete as possible in documenting these so that
when people go look for the part numbers, they can at least find some
reference to them.

Thierry

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