linux-kernel - Re: [PATCH v2 2/3] coresight: funnel: Support static funnel

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Message-ID: <ecfa879e-9fd9-0815-d2da-bb9870d6ae59@arm.com>
Date:   Wed, 20 Mar 2019 13:52:58 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     shiwanglai@...ilicon.com, mathieu.poirier@...aro.org,
        robh+dt@...nel.org, mark.rutland@....com, xuwei5@...ilicon.com,
        alexander.shishkin@...ux.intel.com
Cc:     linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, leo.yan@...aro.org,
        suzhuangluan@...ilicon.com
Subject: Re: [PATCH v2 2/3] coresight: funnel: Support static funnel



On 20/03/2019 12:38, Wanglai Shi wrote:
> From: Leo Yan <leo.yan@...aro.org>
> 
> 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.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---

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

> -static const struct amba_id funnel_ids[] = {
> +static int static_funnel_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +
> +	pm_runtime_get_noresume(&pdev->dev);
> +	pm_runtime_set_active(&pdev->dev);
> +	pm_runtime_enable(&pdev->dev);
> +
> +	/* Static funnel do not have programming base */
> +	ret = funnel_probe(&pdev->dev, NULL);
> +
> +	if (ret) {
> +		pm_runtime_put_noidle(&pdev->dev);
> +		pm_runtime_disable(&pdev->dev);
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct of_device_id static_funnel_match[] = {
> +	{.compatible = "arm,coresight-funnel"},

There is a potential issue with re-using the "compatible" string
already reserved for the normal programmable funnel. We may handle
a programmable funnel as non-programmable one, which is not good.

Do we need to use "arm,coresight-static-funnel" ?

Otherwise, looks good to me.

Suzuki