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

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Message-ID: <f4db016a-0c57-4213-8eca-75a090d7aabb@arm.com>
Date: Wed, 7 May 2025 12:59:33 +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 07/05/2025 09:52, Suzuki K Poulose wrote:
> On 07/05/2025 05:26, Yuanfang Zhang wrote:
>>
>>
>> On 5/6/2025 7:20 PM, Suzuki K Poulose wrote:
>>> 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
>>>
>> yes, now only describe the TNOCs which need traceID, Video TNOC is 
>> another type, it is interconnect TNOC which collects trace from 
>> subsystems
>> and transfers Aggr TNOC, it doesn't have ATID. Its driver is different 
>> from this patch, I want to describe it when upstream its driver.

So, if both are TNOC and there different types of them, how do you plan
to identify, which is what ?

And we also have a dt-bindings which simply says "coresight-tnoc". Isn't 
too generic if it is meant to be "aggregator" ?

Suzuki



> 
> Thanks! Please could you make sure to describe all of this when sending
> out a patch in the cover letter ?
> 
> Cheers
> Suzuki
> 
> 
>>
>> Yuanfang
>>
>>
>>
>>
>>
>>
>