linux-kernel - Re: [PATCH v3 2/2] coresight: add coresight Trace Network On Chip driver

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Message-ID: <9b75b9d1-a9ed-46c9-9dba-8e3eb261dcc0@arm.com>
Date: Tue, 6 May 2025 12:20:42 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Yuanfang Zhang <quic_yuanfang@...cinc.com>,
 Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: kernel@....qualcomm.com, linux-arm-msm@...r.kernel.org,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] coresight: add coresight Trace Network On Chip
 driver

On 14/04/2025 10:16, Yuanfang Zhang wrote:
> 
> 
> On 4/11/2025 5:59 PM, Suzuki K Poulose wrote:
>> On 11/04/2025 09:57, Yuanfang Zhang wrote:
>>> Add a driver to support Coresight device Trace Network On Chip (TNOC),
>>> which is an integration hierarchy integrating functionalities of TPDA
>>> and funnels. It aggregates the trace and transports to coresight trace
>>> bus.
>>>
>>> Compared to current configuration, it has the following advantages:
>>> 1. Reduce wires between subsystems.
>>> 2. Continue cleaning the infrastructure.
>>> 3. Reduce Data overhead by transporting raw data from source to target.
>>>
>>>     +------------------------+                +-------------------------+
>>>     | Video Subsystem        |                |Video Subsystem          |
>>>     |       +-------------+  |                |       +------------+    |
>>>     |       | Video TPDM  |  |                |       | Video TPDM |    |
>>>     |       +-------------+  |                |       +------------+    |
>>>     |            |           |                |              |          |
>>>     |            v           |                |              v          |
>>>     |   +---------------+    |                |        +-----------+    |
>>>     |   | Video funnel  |    |                |        |Video TNOC |    |
>>>     |   +---------------+    |                |        +-----------+    |
>>>     +------------|-----------+                +------------|------------+
>>>                  |                                         |
>>>                  v-----+                                   |
>>> +--------------------|---------+                         |
>>> |  Multimedia        v         |                         |
>>> |  Subsystem   +--------+      |                         |
>>> |              |  TPDA  |      |                         v
>>> |              +----|---+      |              +---------------------+
>>> |                   |          |              |    Aggregator TNOC  |
>>> |                   |          |              +----------|----------+
>>> |                   +--        |                         |
>>> |                     |        |                         |
>>> |                     |        |                         |
>>> |              +------v-----+  |                         |
>>> |              |  Funnel    |  |                         |
>>> |              +------------+  |                         |
>>> +----------------|-------------+                         |
>>>                    |                                       |
>>>                    v                                       v
>>>         +--------------------+                    +------------------+
>>>         |   Coresight Sink   |                    |  Coresight Sink  |
>>>         +--------------------+                    +------------------+
>>
>> If each NOC has TraceID, how do you reliably decode the trace ?
>> Is there a single NOC/TPDA in the path from Source to sink ?
> 
> Not each TNOC has TraceID, there is only one TNOC has TraceID for one path
> from Source to sink. In the example, only the aggregator TNOC has traceID.
> Decode trace relying on TraceID + Inport number.
> It can has mutiple TNOC/TPDA in one path.

So do we only describe the TNOCs that need traceId in the DT ? (e.g., 
Aggregator TNOC above ?) How about Video TNOC ? Don't we allocate a
trace id for it by default, when it is described ?

Suzuki