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SubjectRe: [PATCH 11/13] dt-bindings: mips: Add loongson cpus & boards
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Hi guys,

On Tue, Aug 27, 2019 at 10:18:46PM +0800, Jiaxun Yang wrote:
> On 2019/8/27 下午8:45, Rob Herring wrote:
> > On Tue, Aug 27, 2019 at 3:55 AM Jiaxun Yang <jiaxun.yang@flygoat.com> wrote:
> > > diff --git a/Documentation/devicetree/bindings/mips/loongson/cpus.yaml b/Documentation/devicetree/bindings/mips/loongson/cpus.yaml
> > > new file mode 100644
> > > index 000000000000..410d896a0078
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/mips/loongson/cpus.yaml
> > > @@ -0,0 +1,38 @@
> > > +# SPDX-License-Identifier: GPL-2.0
> > Dual license for new bindings please:
> >
> > (GPL-2.0-only OR BSD-2-Clause)
> >
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/mips/loongson/cpus.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Loongson CPUs bindings
> > > +
> > > +maintainers:
> > > + - Jiaxun Yang <jiaxun.yang@flygoat.com>
> > > +
> > > +description: |+
> > > + The device tree allows to describe the layout of CPUs in a system through
> > > + the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
> > > + defining properties for every cpu.
> > > +
> > > + Bindings for CPU nodes follow the Devicetree Specification, available from:
> > > +
> > > + https://www.devicetree.org/specifications/
> > > +
> > > +properties:
> > > + reg:
> > > + maxItems: 1
> > > + description: |
> > > + Physical ID of a CPU, Can be read from CP0 EBase.CPUNum.
> > Is this definition specific to Loongson CPUs or all MIPS?
>
> Currently it's specific to Loongson CPU only, as other processors may using
> different method to express CPU map.
>
> Different from Arm, MIPS family of processors seems less uniform and have
> their own designs.
>
> For this point, we'd better ask Paul's opinion.

In general on MIPS we detect CPU properties at runtime from coprocessor
0 registers & similar sources of information, so there's not really a
need to specify anything about the CPU in devicetree. For example here
you say yourself that the value for this property can be read from
EBase.CPUNum - so why specify it in DT?

Thanks,
Paul
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