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

Suzuki K Poulose
2021-02-10T12:35:14Z

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@arm.com>
>>
>> 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@vger.kernel.org
>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>> Cc: Mike Leach <mike.leach@linaro.org>
>> Cc: Rob Herring <robh@kernel.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> 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@arm.com>
>> + - Mathieu Poirier <mathieu.poirier@linaro.org>
>> +
>> +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@arm.com
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