Re: [PATCH v2 3/3] coresight: dummy: Add reserve atid support for dummy source

[James Clark <james.clark@arm.com>]

On 03/06/2024 10:43, Mao Jinlong wrote:
> Some dummy source has static trace id configured in HW and it cannot
> be changed via software programming. Configure the trace id in device
> tree and reserve the id when device probe.
> 
> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
> ---
>  .../sysfs-bus-coresight-devices-dummy-source  | 15 +++++
>  drivers/hwtracing/coresight/coresight-dummy.c | 58 +++++++++++++++++--
>  2 files changed, 69 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-dummy-source
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-dummy-source b/Documentation/ABI/testing/sysfs-bus-coresight-devices-dummy-source
> new file mode 100644
> index 000000000000..d93c198115c9
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-dummy-source
> @@ -0,0 +1,15 @@
> +What:		/sys/bus/coresight/devices/dummy_source<N>/enable_source
> +Date:		June 2024
> +KernelVersion:	6.9
> +Contact:	Mao Jinlong <quic_jinlmao@quicinc.com>
> +Description:	(RW) Enable/disable tracing of dummy source. A sink should be activated
> +		before enabling the source. The path of coresight components linking
> +		the source to the sink is configured and managed automatically by the
> +		coresight framework.
> +
> +What:		/sys/bus/coresight/devices/dummy_source<N>/traceid
> +Date:		June 2024
> +KernelVersion:	6.9
> +Contact:	Mao Jinlong <quic_jinlmao@quicinc.com>
> +Description:	(R) Show the trace ID that will appear in the trace stream
> +		coming from this trace entity.
> diff --git a/drivers/hwtracing/coresight/coresight-dummy.c b/drivers/hwtracing/coresight/coresight-dummy.c
> index ac70c0b491be..1f7133ac2c0b 100644
> --- a/drivers/hwtracing/coresight/coresight-dummy.c
> +++ b/drivers/hwtracing/coresight/coresight-dummy.c
> @@ -11,10 +11,12 @@
>  #include <linux/pm_runtime.h>
>  
>  #include "coresight-priv.h"
> +#include "coresight-trace-id.h"
>  
>  struct dummy_drvdata {
>  	struct device			*dev;
>  	struct coresight_device		*csdev;
> +	u8				traceid;
>  };
>  
>  DEFINE_CORESIGHT_DEVLIST(source_devs, "dummy_source");
> @@ -67,6 +69,32 @@ static const struct coresight_ops dummy_sink_cs_ops = {
>  	.sink_ops = &dummy_sink_ops,
>  };
>  
> +/* User can get the trace id of dummy source from this node. */
> +static ssize_t traceid_show(struct device *dev,
> +			    struct device_attribute *attr, char *buf)
> +{
> +	unsigned long val;
> +	struct dummy_drvdata *drvdata = dev_get_drvdata(dev->parent);
> +
> +	val = drvdata->traceid;
> +	return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
> +}
> +static DEVICE_ATTR_RO(traceid);
> +
> +static struct attribute *coresight_dummy_attrs[] = {
> +	&dev_attr_traceid.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group coresight_dummy_group = {
> +	.attrs = coresight_dummy_attrs,
> +};
> +
> +static const struct attribute_group *coresight_dummy_groups[] = {
> +	&coresight_dummy_group,
> +	NULL,
> +};
> +
>  static int dummy_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -74,6 +102,11 @@ static int dummy_probe(struct platform_device *pdev)
>  	struct coresight_platform_data *pdata;
>  	struct dummy_drvdata *drvdata;
>  	struct coresight_desc desc = { 0 };
> +	int ret, trace_id;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
>  
>  	if (of_device_is_compatible(node, "arm,coresight-dummy-source")) {
>  
> @@ -85,6 +118,24 @@ static int dummy_probe(struct platform_device *pdev)
>  		desc.subtype.source_subtype =
>  					CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS;
>  		desc.ops = &dummy_source_cs_ops;
> +		desc.groups = coresight_dummy_groups;
> +
> +		ret = coresight_get_source_traceid(dev, &trace_id);
> +		if (!ret) {
> +			ret = coresight_trace_id_get_system_id(trace_id);
> +			if (ret < 0)
> +				return ret;
> +
> +			drvdata->traceid = ret;
> +		} else {
> +			trace_id = coresight_trace_id_get_system_id(0);
> +			if (trace_id < 0) {
> +				ret = trace_id;
> +				return ret;
> +			}
> +			drvdata->traceid = (u8)trace_id;
> +		}
> +

It's a bit weird to use ret in one version and trace_id in the other.
And one casts to (u8) but the other doesn't. I'm sure it all compiles to
the same in the end but it would be a bit more readable if it was more
consistent.

>  	} else if (of_device_is_compatible(node, "arm,coresight-dummy-sink")) {
>  		desc.name = coresight_alloc_device_name(&sink_devs, dev);
>  		if (!desc.name)
> @@ -103,10 +154,6 @@ static int dummy_probe(struct platform_device *pdev)
>  		return PTR_ERR(pdata);
>  	pdev->dev.platform_data = pdata;
>  
> -	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> -	if (!drvdata)
> -		return -ENOMEM;
> -
>  	drvdata->dev = &pdev->dev;
>  	platform_set_drvdata(pdev, drvdata);
>  
> @@ -126,7 +173,10 @@ static void dummy_remove(struct platform_device *pdev)
>  {
>  	struct dummy_drvdata *drvdata = platform_get_drvdata(pdev);
>  	struct device *dev = &pdev->dev;
> +	struct device_node *node = dev->of_node;
>  
> +	if (of_device_is_compatible(node, "arm,coresight-dummy-source"))
> +		coresight_trace_id_put_system_id(drvdata->traceid);
>  	pm_runtime_disable(dev);
>  	coresight_unregister(drvdata->csdev);
>  }