linux-kernel - Re: [PATCH v1 0/3] coresight: Support for building more coresight paths

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Message-ID: <070d1c13-2b3e-2dfb-f51b-9d40f1b45a03@arm.com>
Date:   Mon, 10 May 2021 14:10:52 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Tao Zhang <taozha@...eaurora.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Tingwei Zhang <tingwei@...eaurora.org>,
        Mao Jinlong <jinlmao@...eaurora.org>,
        Yuanfang Zhang <zhangyuanfang@...eaurora.org>
Subject: Re: [PATCH v1 0/3] coresight: Support for building more coresight
 paths

Hi Tao

On 10/05/2021 12:05, Tao Zhang wrote:
> We are trying to achieve more types of Coresight source devices.
> For example, we have a type of coresight source devic named TPDM.
> In the process of using, sometimes mulitiple TPDMs need to be
> connected to the different input ports on the same funnel.
> Meanwhile, these TPDMs also need to output from different
> ports on the funnel.
> But, at present the Coresight driver assumes
> a) Only support Coresight source type ETM, ETR and ETF

Did you mean ETM and STM here ? ETR & ETF are not source types, rather
they are SINK.


> b) Funnels only support mulitiple inputs and one output
> Which doesn't help to add the above feature for our new Coresight
> source device TPDM. So, in order to accommodate the new device,
> we develop the following patches.

Where is the TPDM driver ? Could you give us a rough idea of the 
behavior in terms of the input / output ?


> a) Add support more types of Coresight source devices.

Which ones ? where is the code ?

> b) Add support for multiple output ports on funnel and the output
> ports could be selected by Corsight source.

Does the "TPDM" require programming to switch these output or are these 
"static" ?

Is this something that can be avoided by having a "fake" 
static-replicator in the path ?

e.g,              TPDM
	 ________________________________________________
  In0	|						|  -> Out0
  In1	|   Static-Funnel   -> Static-Replicator	|  -> Out1
  In2	|						|  -> Out2
	 ________________________________________________


Is this something that can be solved ? Again, please give a brief
description of the TPDM device and the driver code in the series to
give us a complete picture of what you are trying to do.

Reviewing some changes without having the full picture is not going to 
be helpful.

Suzuki