linux-kernel - Re: [PATCH v4 04/11] coresight-tpdm: Add reset node to TPDM node

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Date:   Tue, 23 May 2023 15:53:06 +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 v4 04/11] coresight-tpdm: Add reset node to TPDM node

On 27/04/2023 10:00, Tao Zhang wrote:
> TPDM device need a node to reset the configurations and status of
> it. This change provides a node to reset the configurations and
> disable the TPDM if it has been enabled.
> 
> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
> ---
>   .../ABI/testing/sysfs-bus-coresight-devices-tpdm   | 10 ++++++++
>   drivers/hwtracing/coresight/coresight-tpdm.c       | 27 ++++++++++++++++++++++
>   2 files changed, 37 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
> index 4a58e64..686bdde 100644
> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
> @@ -11,3 +11,13 @@ Description:
>   		Accepts only one of the 2 values -  1 or 2.
>   		1 : Generate 64 bits data
>   		2 : Generate 32 bits data
> +
> +What:		/sys/bus/coresight/devices/<tpdm-name>/reset
> +Date:		March 2023
> +KernelVersion	6.3
> +Contact:	Jinlong Mao (QUIC) <quic_jinlmao@...cinc.com>, Tao Zhang (QUIC) <quic_taozha@...cinc.com>
> +Description:
> +		(Write) Reset the dataset of the tpdm, and disable the tpdm.
> +
> +		Accepts only one value -  1.
> +		1 : Reset the dataset of the tpdm
> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c b/drivers/hwtracing/coresight/coresight-tpdm.c
> index 6f8a8ab..2e64cfd 100644
> --- a/drivers/hwtracing/coresight/coresight-tpdm.c
> +++ b/drivers/hwtracing/coresight/coresight-tpdm.c
> @@ -164,6 +164,32 @@ static int tpdm_datasets_setup(struct tpdm_drvdata *drvdata)
>   	return 0;
>   }
>   
> +static ssize_t reset_store(struct device *dev,
> +					  struct device_attribute *attr,
> +					  const char *buf,
> +					  size_t size)
> +{
> +	int ret = 0;
> +	unsigned long val;
> +	struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +
> +	ret = kstrtoul(buf, 10, &val);
> +	if (ret || val != 1)
> +		return -EINVAL;
> +
> +	spin_lock(&drvdata->spinlock);
> +	tpdm_reset_datasets(drvdata);
> +
> +	spin_unlock(&drvdata->spinlock);
> +
> +	/* Disable tpdm if enabled */
> +	if (drvdata->enable)
> +		coresight_disable_source(drvdata->csdev, NULL);

I am not really keen on doing this behind the back. What about the path 
of components ? We could simply reject the request when the TPDA is 
enabled and let the user alway follow :
	1) Disable the TPDM manually via sysfs
   	2) Reset the TPDM.

So, please remove the disable step here.

Suzuki


> +
> +	return size;
> +}
> +static DEVICE_ATTR_WO(reset);
> +
>   /*
>    * value 1: 64 bits test data
>    * value 2: 32 bits test data
> @@ -204,6 +230,7 @@ static ssize_t integration_test_store(struct device *dev,
>   static DEVICE_ATTR_WO(integration_test);
>   
>   static struct attribute *tpdm_attrs[] = {
> +	&dev_attr_reset.attr,
>   	&dev_attr_integration_test.attr,
>   	NULL,
>   };