Re: [PATCH v4 15/19] dts: bindings: Document device tree bindings for ETE

From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Rob Herring <robh@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mathieu.poirier@linaro.org,
	mike.leach@linaro.org, anshuman.khandual@arm.com,
	leo.yan@linaro.org, devicetree@vger.kernel.org
Subject: Re: [PATCH v4 15/19] dts: bindings: Document device tree bindings for ETE
Date: Mon, 22 Mar 2021 16:53:15 +0000	[thread overview]
Message-ID: <f69ad530-baec-2e73-827a-b5a5a6df3d23@arm.com> (raw)
In-Reply-To: <20210306210627.GA1207387@robh.at.kernel.org>

Hi Rob

On 06/03/2021 21:06, Rob Herring wrote:
> On Thu, Feb 25, 2021 at 07:35:39PM +0000, Suzuki K Poulose wrote:
>> 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>
>> ---
>> Changes:
>>   - Fix out-ports defintion
>> ---
>>   .../devicetree/bindings/arm/ete.yaml          | 71 +++++++++++++++++++
>>   1 file changed, 71 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 000000000000..35a42d92bf97
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/ete.yaml
>> @@ -0,0 +1,71 @@
>> +# 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:
>> +    description: |
>> +      Handle to the cpu this ETE is bound to.
>> +    $ref: /schemas/types.yaml#/definitions/phandle
>> +
>> +  out-ports:
>> +    description: |
>> +      Output connections from the ETE to legacy CoreSight trace bus.
>> +    $ref: /schemas/graph.yaml#/properties/port
> 
> s/port/ports/

Ok.

> 
> And then you need:
> 
>         properties:
>           port:
>             description: what this port is
>             $ref: /schemas/graph.yaml#/properties/port

Isn't this already covered by the definition of ports ? There are no 
fixed connections for ETE. It is optional and could be connected to
any legacy CoreSight component. i.e, a "ports" object can have port
objects inside.

Given we have defined out-ports as an object "confirming to the ports"
do we need to describe the individual port nodes ?

Cheers
Suzuki