coresight: dummy: Add static trace id support for dummy source

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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
[ Fix Date and Version to December 2024, v6.14 ]
Signed-off-by: Suzuki K Poulose <[e-mail]>

Documentation/ABI/testing/sysfs-bus-coresight-devices-dummy-source

···
+What:		/sys/bus/coresight/devices/dummy_source<N>/enable_source
+Date:		Dec 2024
+KernelVersion:	6.14
+Contact:	Mao Jinlong <[e-mail]>
+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:		Dec 2024
+KernelVersion:	6.14
+Contact:	Mao Jinlong <[e-mail]>
+Description:	(R) Show the trace ID that will appear in the trace stream
+		coming from this trace entity.

drivers/hwtracing/coresight/coresight-dummy.c

···
 #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");
···
 	.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 sysfs_emit(buf, "%#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;
···
 	struct coresight_platform_data *pdata;
 	struct dummy_drvdata *drvdata;
 	struct coresight_desc desc = { 0 };
+	int ret = 0, trace_id = 0;
+
+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
 
 	if (of_device_is_compatible(node, "arm,coresight-dummy-source")) {
 
···
 		desc.subtype.source_subtype =
 					CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS;
 		desc.ops = &dummy_source_cs_ops;
+		desc.groups = coresight_dummy_groups;
+
+		ret = coresight_get_static_trace_id(dev, &trace_id);
+		if (!ret) {
+			/* Get the static id if id is set in device tree. */
+			ret = coresight_trace_id_get_static_system_id(trace_id);
+			if (ret < 0) {
+				dev_err(dev, "Fail to get static id.\n");
+				return ret;
+			}
+		} else {
+			/* Get next available id if id is not set in device tree. */
+			trace_id = coresight_trace_id_get_system_id();
+			if (trace_id < 0) {
+				ret = trace_id;
+				return ret;
+			}
+		}
+		drvdata->traceid = (u8)trace_id;
+
 	} else if (of_device_is_compatible(node, "arm,coresight-dummy-sink")) {
 		desc.name = coresight_alloc_device_name(&sink_devs, dev);
 		if (!desc.name)
···
 	}
 
 	pdata = coresight_get_platform_data(dev);
-	if (IS_ERR(pdata))
-		return PTR_ERR(pdata);
+	if (IS_ERR(pdata)) {
+		ret = PTR_ERR(pdata);
+		goto free_id;
+	}
 	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);
···
 	desc.pdata = pdev->dev.platform_data;
 	desc.dev = &pdev->dev;
 	drvdata->csdev = coresight_register(&desc);
-	if (IS_ERR(drvdata->csdev))
-		return PTR_ERR(drvdata->csdev);
+	if (IS_ERR(drvdata->csdev)) {
+		ret = PTR_ERR(drvdata->csdev);
+		goto free_id;
+	}
 
 	pm_runtime_enable(dev);
 	dev_dbg(dev, "Dummy device initialized\n");
 
-	return 0;
+	ret = 0;
+	goto out;
+
+free_id:
+	if (IS_VALID_CS_TRACE_ID(drvdata->traceid))
+		coresight_trace_id_put_system_id(drvdata->traceid);
+
+out:
+	return ret;
 }
 
 static void dummy_remove(struct platform_device *pdev)
···
 	struct dummy_drvdata *drvdata = platform_get_drvdata(pdev);
 	struct device *dev = &pdev->dev;
 
+	if (IS_VALID_CS_TRACE_ID(drvdata->traceid))
+		coresight_trace_id_put_system_id(drvdata->traceid);
 	pm_runtime_disable(dev);
 	coresight_unregister(drvdata->csdev);
 }