linux-kernel - Re: [PATCH v6 6/8] coresight: add support for CPU debug module

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Message-ID: <20170419150753.GA23319@leoy-linaro>
Date:   Wed, 19 Apr 2017 23:07:53 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Suzuki K Poulose <Suzuki.Poulose@....com>
Cc:     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>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        Mike Leach <mike.leach@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v6 6/8] coresight: add support for CPU debug module

On Wed, Apr 19, 2017 at 03:32:39PM +0100, Suzuki K Poulose wrote:

[...]

> >>>+static int debug_probe(struct amba_device *adev, const struct amba_id *id)
> >>>+{
> >>>+	void __iomem *base;
> >>>+	struct device *dev = &adev->dev;
> >>>+	struct debug_drvdata *drvdata;
> >>>+	struct resource *res = &adev->res;
> >>>+	struct device_node *np = adev->dev.of_node;
> >>>+	int ret;
> >>>+
> >>>+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> >>>+	if (!drvdata)
> >>>+		return -ENOMEM;
> >>>+
> >>>+	drvdata->cpu = np ? of_coresight_get_cpu(np) : 0;
> >>>+	if (per_cpu(debug_drvdata, drvdata->cpu)) {
> >>>+		dev_err(dev, "CPU%d drvdata has been initialized\n",
> >>>+			drvdata->cpu);
> >>
> >>May be we could warn about a possible issue in the DT ?
> >
> >So can I understand the suggestion is to add warning in function
> >of_coresight_get_cpu() when cannot find CPU number, and here directly
> >bail out?
> 
> No. One could have single CPU DT, where he doesn't need to provide the CPU number.
> Hence, it doesn't make sense to WARN  in of_coresight_get_cpu().
> 
> But when we hit the case above, we find that the some node was registered for
> the given CPU (be it 0 or any other), which is definitely an error in DT. Due to
> 
> 1) Hasn't specified the CPU number for more than one node
> 
> OR
> 
> 2) CPU number duplicated in the more than one nodes.

Thanks for explaination. It's clear for me now.

> Cheers
> Suzuki