linux-kernel - Re: [PATCH v3 2/2] coresight: funnel: Support static funnel

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Message-ID: <799f3f27-6a20-836e-b699-252ebb8e2fdf@arm.com>
Date:   Thu, 28 Mar 2019 19:26:16 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     leo.yan@...aro.org, mathieu.poirier@...aro.org, robh+dt@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
        shiwanglai@...ilicon.com
Subject: Re: [PATCH v3 2/2] coresight: funnel: Support static funnel

On 03/28/2019 02:35 AM, Leo Yan wrote:
> Since CoreSight hardware topology can use a 'hidden' funnel in the
> trace data path, this kind funnel doesn't have register for accessing
> and is used by default from hardware design perspective.  Below is an
> example for related hardware topology:
> 
>    +------+  +------+
>    | cpu0 |->| ETM  |-\
>    +------+  +------+  \-> +--------+  +-----+
>     ......                 | Funnel |->| ETF |-\    Hidden funnel
>    +------+  +------+  /-> +--------+  +-----+  \        |
>    | cpu3 |->| ETM  |-/                          \       V
>    +------+  +------+                             \-> +--------+
>                                                       | Funnel |-> ...
>    +------+  +------+                             /-> +--------+
>    | cpu4 |->| ETM  |-\                          /
>    +------+  +------+  \-> +--------+  +-----+  /
>     ......                 | Funnel |->| ETF |-/
>    +------+  +------+  /-> +--------+  +-----+
>    | cpu7 |->| ETM  |-/
>    +------+  +------+
> 
> The CoreSight funnel driver only supports dynamic funnel with
> registration register resource, thus it cannot support for the static
> funnel case and it's impossible to create trace data path for this case.
> 
> This patch is to extend CoreSight funnel driver to support both for
> static funnel and dynamic funnel.  For the dynamic funnel it reuses the
> code existed in the driver, for static funnel the driver will support
> device probe if without providing register resource and the driver skips
> registers accessing when detect the register base is NULL.
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: Wanglai Shi <shiwanglai@...ilicon.com>
> Suggested-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>