linux-kernel - Re: [PATCH] coresight: cti: Check if the CPU activated for the CPU CTI

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Date:   Mon, 27 Mar 2023 10:52:03 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Tao Zhang <quic_taozha@...cinc.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Jinlong Mao <quic_jinlmao@...cinc.com>,
        Leo Yan <leo.yan@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org
Subject: Re: [PATCH] coresight: cti: Check if the CPU activated for the CPU
 CTI

On 27/03/2023 10:49, Tao Zhang wrote:
> Check whether the CPU corresponding to the CPU CTI is activated.
> If it is not activated, the CPU CTI node should not exist, and
> an error will be returned in the initialization function.
> 
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> ---
>   drivers/hwtracing/coresight/coresight-cti-core.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
> index 277c890..aaa83ae 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
> @@ -899,10 +899,12 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
>   	drvdata->config.hw_powered = true;
>   
>   	/* set up device name - will depend if cpu bound or otherwise */
> -	if (drvdata->ctidev.cpu >= 0)
> +	if (drvdata->ctidev.cpu >= 0) {
> +		if (!cpu_active(drvdata->ctidev.cpu))
> +			return -ENXIO;
>   		cti_desc.name = devm_kasprintf(dev, GFP_KERNEL, "cti_cpu%d",
>   					       drvdata->ctidev.cpu);

But why ? As long as we do not enable or touch any CPU specific bits in 
the probe, why do we need to fail this ? What are you trying to fix ?

Please could you share the log if you are hitting something ? This looks
like masking a problem.

Suzuki


> -	else
> +	} else
>   		cti_desc.name = coresight_alloc_device_name(&cti_sys_devs, dev);
>   	if (!cti_desc.name)
>   		return -ENOMEM;