linux-kernel - Re: [PATCH v4 17/19] coresight: core: Add support for dedicated percpu sinks

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Message-ID: <4fe2cce5-74b5-7ced-1a16-1dde90b920e2@arm.com>
Date:   Mon, 22 Mar 2021 16:57:45 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mike Leach <mike.leach@...aro.org>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Leo Yan <leo.yan@...aro.org>
Subject: Re: [PATCH v4 17/19] coresight: core: Add support for dedicated
 percpu sinks

Hi Mike

On 08/03/2021 17:26, Mike Leach wrote:

> Hi,
> 
> On Thu, 25 Feb 2021 at 19:36, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>>
>> From: Anshuman Khandual <anshuman.khandual@....com>
>>
>> Add support for dedicated sinks that are bound to individual CPUs. (e.g,
>> TRBE). To allow quicker access to the sink for a given CPU bound source,
>> keep a percpu array of the sink devices. Also, add support for building
>> a path to the CPU local sink from the ETM.
>>
>> This adds a new percpu sink type CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM.
>> This new sink type is exclusively available and can only work with percpu
>> source type device CORESIGHT_DEV_SUBTYPE_SOURCE_PROC.
>>
> 
> Minor nit:  FEAT_TRBE architecturally guarantees a compatible
> architectural FEAT_ETE source.
> However _all_ CPU sources have CORESIGHT_DEV_SUBTYPE_SOURCE_PROC set,
> ETMv3.x, PTM, ETM4.x and ETE alike.
> In the code that follows - coresight_is_percpu_source() checks it is
> any type of CPU source, not the FEAT_ETE type, which is fine as we
> then check the cpu and if it has TRBE.

Agreed. But we would like to keep this CoreSight generic code away from 
the specifics of underlying "source", which is why we used the generic 
notion of a per-CPU source.

> So the simplifications to the code from the first couple of patch sets
> make this explanation slightly misleading. Could do to adjust if
> re-spinning set.
> 
> Reviewed-by: Mike Leach <mike.leach@...aro.org>

Thanks
Suzuki