Re: [PATCH V3 06/14] dts: bindings: Document device tree bindings for ETE

[Suzuki K Poulose]

Hi Rob

On 2/9/21 7:00 PM, Rob Herring wrote:
> On Wed, Jan 27, 2021 at 02:25:30PM +0530, Anshuman Khandual wrote:
> > From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> >
> > Document the device tree bindings for Embedded Trace Extensions.
> > ETE can be connected to legacy coresight components and thus
> > could optionally contain a connection graph as described by
> > the CoreSight bindings.
> >
> > Cc: devicetree@xxxxxxxxxxxxxxx
> > Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> > Cc: Rob Herring <robh@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > ---
> > Changes in V3:
> >
> > - Fixed all DT yaml semantics problems
> >
> >   Documentation/devicetree/bindings/arm/ete.yaml | 74 ++++++++++++++++++++++++++
> >   1 file changed, 74 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/arm/ete.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/arm/ete.yaml b/Documentation/devicetree/bindings/arm/ete.yaml
> > new file mode 100644
> > index 0000000..edc1fe2
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/arm/ete.yaml
> > @@ -0,0 +1,74 @@
> > +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> > +# Copyright 2021, Arm Ltd
> > +%YAML 1.2
> > +---
> > +$id: "http://devicetree.org/schemas/arm/ete.yaml#";
> > +$schema: "http://devicetree.org/meta-schemas/core.yaml#";
> > +
> > +title: ARM Embedded Trace Extensions
> > +
> > +maintainers:
> > +  - Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > +  - Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > +
> > +description: |
> > +  Arm Embedded Trace Extension(ETE) is a per CPU trace component that
> > +  allows tracing the CPU execution. It overlaps with the CoreSight ETMv4
> > +  architecture and has extended support for future architecture changes.
> > +  The trace generated by the ETE could be stored via legacy CoreSight
> > +  components (e.g, TMC-ETR) or other means (e.g, using a per CPU buffer
> > +  Arm Trace Buffer Extension (TRBE)). Since the ETE can be connected to
> > +  legacy CoreSight components, a node must be listed per instance, along
> > +  with any optional connection graph as per the coresight bindings.
> > +  See bindings/arm/coresight.txt.
> > +
> > +properties:
> > +  $nodename:
> > +    pattern: "^ete([0-9a-f]+)$"
> > +  compatible:
> > +    items:
> > +      - const: arm,embedded-trace-extension
> > +
> > +  cpu:
>
> We've already established 'cpus' for this purpose.

Please see : https://lkml.kernel.org/r/9417218b-6eda-373b-a2cb-869089ffc7cd@xxxxxxx
for my response in the previous version to this and the one with out-ports.

> > +    description: |
> > +      Handle to the cpu this ETE is bound to.
> > +    $ref: /schemas/types.yaml#/definitions/phandle
> > +
> > +  out-ports:
> > +    type: object
>
> Replace with: $ref: /schemas/graph.yaml#/properties/ports

So, just to confirm again :
The CoreSight graph bindings expect the input ports and output ports
grouped under in-ports{} and out-ports{} respectively to avoid having
to specify the direction of the ports in the individual "port" nodes.
i.e

in-ports {

	property: ports
	  OR
	property: port

	required:
		OneOf:
			ports
			port
}

out-ports {

	# same as above
}

So thats why I added out-ports as a new object, where the ports/port
could be a child node.

Ideally the definition of out-ports /in-ports should go to a common schema
for CoreSight bindings, when we move to Yaml for the existing bindings,
which will follow in a separate series, later.

> > +    description: |
> > +      Output connections from the ETE to legacy CoreSight trace bus.
> > +    properties:
> > +      port:
> > +        $ref: /schemas/graph.yaml#/properties/port
>
> Actually, if only 1 port ever, you can drop 'out-ports' and just have
> 'port'. Not sure though if the coresight stuff depends on 'out-ports'.

Cheers
Suzuki