linux-kernel - Re: [PATCH v8 5/7] coresight: add support for CPU debug module

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Date:   Fri, 5 May 2017 09:34:44 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Leo Yan <leo.yan@...aro.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Wei Xu <xuwei5@...ilicon.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Mike Leach <mike.leach@...aro.org>
Subject: Re: [PATCH v8 5/7] coresight: add support for CPU debug module

On 5 May 2017 at 09:04, Sudeep Holla <sudeep.holla@....com> wrote:
>
>
> On 05/05/17 15:48, Mathieu Poirier wrote:
>> On Fri, May 05, 2017 at 02:55:17PM +0100, Sudeep Holla wrote:
>
> [...]
>
>>>
>>> Just curious as why this is not registered under coresight bus using
>>> coresight_register ? It would be good to group all the coresight devices
>>> under that bus if possible.
>>
>> The only thing this driver has in common with the coresight framework is the
>> name, everything else is completely different.  Coupling them together (because
>> of the name) would introduce a lot of hacks and make the code unintelligible.
>>
>
> I guessed so from the quick glance at it as it needs descriptors with
> notion of source, sink and links to register. However I felt odd to not
> group under the same "coresight" bus. As someone with least knowledge
> on coresight, I would check under "sys/bus/coresight" to check available
> devices on the system.

2 years ago when implementing the coresight framework, using
"coresight" sounded like a logical choice but in hindsight it probably
should have been something like coresight-hat (HW Assisted Tracing).
That would have been a better representation of the reality, i.e the
term "coresight" being an umbrella for many kind of technology.  Leo
has done the right thing here with "coresight-cpu-debug".

>
> Anyways that's just my thoughts though I agree with you. It may need
> more refactoring to support that and it will look hackish if we try to
> do that with the code as it stands.
>
> --
> Regards,
> Sudeep