Coresight: Add coresight dummy driver

Some Coresight devices that HLOS don't have permission to access
or configure. Such as Coresight sink EUD, some TPDMs etc. So there
need driver to register dummy devices as Coresight devices. Provide
Coresight API for dummy device operations, such as enabling and
disabling dummy devices. Build the Coresight path for dummy sink or
dummy source for debugging.

Signed-off-by: Hao Zhang <quic_hazha@quicinc.com>

drivers/hwtracing/coresight/Kconfig

@@ -236,4 +236,15 @@ config CORESIGHT_TPDA
 
 	  To compile this driver as a module, choose M here: the module will be
 	  called coresight-tpda.
+
+config CORESIGHT_DUMMY
+	tristate "Dummy driver support"
+	help
+	  Enables support for dummy driver. Dummy driver can be used for
+	  CoreSight sources/sinks that are owned and configured by some
+	  other subsystem and use Linux drivers to configure rest of trace
+	  path.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called coresight-dummy.
 endif

drivers/hwtracing/coresight/Makefile

@@ -30,3 +30,4 @@ obj-$(CONFIG_CORESIGHT_TPDA) += coresight-tpda.o
 coresight-cti-y := coresight-cti-core.o	coresight-cti-platform.o \
 		   coresight-cti-sysfs.o
 obj-$(CONFIG_ULTRASOC_SMB) += ultrasoc-smb.o
+obj-$(CONFIG_CORESIGHT_DUMMY) += coresight-dummy.o

drivers/hwtracing/coresight/coresight-dummy.c

@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/coresight.h>
+#include <linux/of.h>
+#include <linux/pm_runtime.h>
+
+#include "coresight-priv.h"
+#include "coresight-trace-id.h"
+
+struct dummy_drvdata {
+	struct device			*dev;
+	struct coresight_device		*csdev;
+	int				traceid;
+};
+
+DEFINE_CORESIGHT_DEVLIST(dummy_devs, "dummy");
+
+static int dummy_source_enable(struct coresight_device *csdev,
+			       struct perf_event *event, u32 mode)
+{
+	struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	dev_info(drvdata->dev, "Dummy source enabled\n");
+
+	return 0;
+}
+
+static void dummy_source_disable(struct coresight_device *csdev,
+				 struct perf_event *event)
+{
+	struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	dev_info(drvdata->dev, "Dummy source disabled\n");
+}
+
+static int dummy_sink_enable(struct coresight_device *csdev, u32 mode,
+				void *data)
+{
+	struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	dev_info(drvdata->dev, "Dummy sink enabled\n");
+
+	return 0;
+}
+
+static int dummy_sink_disable(struct coresight_device *csdev)
+{
+	struct dummy_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	dev_info(drvdata->dev, "Dummy sink disabled\n");
+
+	return 0;
+}
+
+static const struct coresight_ops_source dummy_source_ops = {
+	.enable		= dummy_source_enable,
+	.disable	= dummy_source_disable,
+};
+
+static const struct coresight_ops_sink dummy_sink_ops = {
+	.enable		= dummy_sink_enable,
+	.disable	= dummy_sink_disable,
+};
+
+static const struct coresight_ops dummy_cs_ops = {
+	.source_ops	= &dummy_source_ops,
+	.sink_ops	= &dummy_sink_ops,
+};
+
+static int dummy_probe(struct platform_device *pdev)
+{
+	int ret, trace_id;
+	struct device *dev = &pdev->dev;
+	struct coresight_platform_data *pdata;
+	struct dummy_drvdata *drvdata;
+	struct coresight_desc desc = { 0 };
+
+	desc.name = coresight_alloc_device_name(&dummy_devs, dev);
+	if (!desc.name)
+		return -ENOMEM;
+
+	pdata = coresight_get_platform_data(dev);
+	if (IS_ERR(pdata))
+		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);
+
+	if (of_property_read_bool(pdev->dev.of_node, "qcom,dummy-source")) {
+		desc.type = CORESIGHT_DEV_TYPE_SOURCE;
+		desc.subtype.source_subtype =
+					CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS;
+	} else if (of_property_read_bool(pdev->dev.of_node,
+					 "qcom,dummy-sink")) {
+		desc.type = CORESIGHT_DEV_TYPE_SINK;
+		desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
+	} else {
+		dev_info(dev, "Device type not set\n");
+		return -EINVAL;
+	}
+
+	desc.ops = &dummy_cs_ops;
+	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);
+
+	trace_id = coresight_trace_id_get_system_id();
+	if (trace_id < 0) {
+		ret = trace_id;
+		goto cs_unregister;
+	}
+	drvdata->traceid = (u8)trace_id;
+
+	pm_runtime_enable(dev);
+	dev_info(dev, "Dummy device initialized\n");
+
+	return 0;
+
+cs_unregister:
+	coresight_unregister(drvdata->csdev);
+
+	return ret;
+}
+
+static int dummy_remove(struct platform_device *pdev)
+{
+	struct dummy_drvdata *drvdata = platform_get_drvdata(pdev);
+	struct device *dev = &pdev->dev;
+
+	coresight_trace_id_put_system_id(drvdata->traceid);
+	pm_runtime_disable(dev);
+	coresight_unregister(drvdata->csdev);
+	return 0;
+}
+
+static const struct of_device_id dummy_match[] = {
+	{.compatible = "qcom,coresight-dummy"},
+	{},
+};
+
+static struct platform_driver dummy_driver = {
+	.probe	= dummy_probe,
+	.remove	= dummy_remove,
+	.driver	= {
+		.name   = "coresight-dummy",
+		.of_match_table = dummy_match,
+	},
+};
+
+int __init dummy_init(void)
+{
+	return platform_driver_register(&dummy_driver);
+}
+module_init(dummy_init);
+
+void __exit dummy_exit(void)
+{
+	platform_driver_unregister(&dummy_driver);
+}
+module_exit(dummy_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("CoreSight dummy source driver");