linux-kernel - Re: [PATCH v1 0/3] Add support to configure Coresight Dummy subunit

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Date:   Fri, 17 Mar 2023 15:40:54 +0800
From:   Hao Zhang <quic_hazha@...cinc.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jonathan Corbet <corbet@....net>
CC:     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>, <devicetree@...r.kernel.org>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Jinlong Mao <quic_jinlmao@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Tao Zhang <quic_taozha@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v1 0/3] Add support to configure Coresight Dummy subunit

Hi Suzuki,

On 3/16/2023 6:55 PM, Suzuki K Poulose wrote:
> On 16/03/2023 03:20, Hao Zhang wrote:
>> Introduction of Coresight Dummy subunit
>> The Coresight Dummy subunit is for Coresight Dummy component, there 
>> are some
>> specific Coresight devices that HLOS don't have permission to access. 
>> Such as
> 
> What is HLOS ?

The term HLOS stands for High Level OS, it means linux in this case. The 
HLOS runs on APPS processor.

>> some TPDMs, they would be configured in NON-HLOS side, but it's 
>> necessary to
> 
> What is NON-HLOS ?

There are some other sub-processors like modem, adsp etc, they do not 
have a High Level OS. The OS in these sub-processors is lightweight, 
less powerful, somewhat real-time, it would be called NON-HLOS.

>> build Coresight path for it to debug. So there need driver to register 
>> dummy
>> devices as Coresight devices.
> 
> Build a path for who to debug ? If this is used by some privileged
> software, shouldn't that do all of the work ?
> 
> Suzuki

There is coresight source or sink in sub-processor, it would be 
configured by NON-HLOS, and need HLOS to configure the last coresight 
components. So we will use dummy source or sink to replace it in HLOS 
side for building the whole path(from source to sink).

Thanks,
Hao

>>
>> Commit link:
>> https://git.codelinaro.org/clo/linux-kernel/coresight/-/tree/coresight-dummy
>>
>> Hao Zhang (3):
>>    Coresight: Add coresight dummy driver
>>    dt-bindings: arm: Add Coresight Dummy Trace YAML schema
>>    Documentation: trace: Add documentation for Coresight Dummy Trace
>>
>>   .../bindings/arm/qcom,coresight-dummy.yaml    | 129 +++++++++++++
>>   .../trace/coresight/coresight-dummy.rst       |  58 ++++++
>>   drivers/hwtracing/coresight/Kconfig           |  11 ++
>>   drivers/hwtracing/coresight/Makefile          |   1 +
>>   drivers/hwtracing/coresight/coresight-dummy.c | 176 ++++++++++++++++++
>>   5 files changed, 375 insertions(+)
>>   create mode 100644 
>> Documentation/devicetree/bindings/arm/qcom,coresight-dummy.yaml
>>   create mode 100644 Documentation/trace/coresight/coresight-dummy.rst
>>   create mode 100644 drivers/hwtracing/coresight/coresight-dummy.c
>>
>