[PATCH v2] coresight: Add a KUnit test for coresight_find_default_sink()

[James Clark]

Add a test to confirm that default sink selection skips over an ETF
and returns an ETR even if it's further away.

This also makes it easier to add new unit tests in the future.

Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
---
Changes in v2:
- Let devm free everything rather than doing individual kfrees:
  "Like with managed drivers, KUnit-managed fake devices are
  automatically cleaned up when the test finishes, but can be manually
  cleaned up early with kunit_device_unregister()."
- Link to v1: https://lore.kernel.org/r/20250225164639.522741-1-james.clark@xxxxxxxxxx
---
 drivers/hwtracing/coresight/Kconfig                |  9 +++
 drivers/hwtracing/coresight/Makefile               |  3 +-
 drivers/hwtracing/coresight/coresight-core.c       |  1 +
 .../hwtracing/coresight/coresight-kunit-tests.c    | 77 ++++++++++++++++++++++
 4 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index ecd7086a5b83..f064e3d172b3 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig
@@ -259,4 +259,13 @@ config CORESIGHT_DUMMY
 
 	  To compile this driver as a module, choose M here: the module will be
 	  called coresight-dummy.
+
+config CORESIGHT_KUNIT_TESTS
+	  tristate "Enable Coresight unit tests"
+	  depends on KUNIT
+	  default KUNIT_ALL_TESTS
+	  help
+	    Enable Coresight unit tests. Only useful for development and not
+	    intended for production.
+
 endif
diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
index 8e62c3150aeb..96f0dfedb1bf 100644
--- a/drivers/hwtracing/coresight/Makefile
+++ b/drivers/hwtracing/coresight/Makefile
@@ -51,5 +51,4 @@ 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
-obj-$(CONFIG_CORESIGHT_CTCU) += coresight-ctcu.o
-coresight-ctcu-y := coresight-ctcu-core.o
+obj-$(CONFIG_CORESIGHT_KUNIT_TESTS) += coresight-kunit-tests.o
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index bd0a7edd38c9..b101aa133ceb 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -959,6 +959,7 @@ coresight_find_default_sink(struct coresight_device *csdev)
 	}
 	return csdev->def_sink;
 }
+EXPORT_SYMBOL_GPL(coresight_find_default_sink);
 
 static int coresight_remove_sink_ref(struct device *dev, void *data)
 {
diff --git a/drivers/hwtracing/coresight/coresight-kunit-tests.c b/drivers/hwtracing/coresight/coresight-kunit-tests.c
new file mode 100644
index 000000000000..a136af05eaf4
--- /dev/null
+++ b/drivers/hwtracing/coresight/coresight-kunit-tests.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <kunit/test.h>
+#include <kunit/device.h>
+#include <linux/coresight.h>
+
+#include "coresight-priv.h"
+
+static struct coresight_device *coresight_test_device(struct device *dev)
+{
+	struct coresight_device *csdev = devm_kcalloc(dev, 1,
+						     sizeof(struct coresight_device),
+						     GFP_KERNEL);
+	csdev->pdata = devm_kcalloc(dev, 1,
+				   sizeof(struct coresight_platform_data),
+				   GFP_KERNEL);
+	return csdev;
+}
+
+static int coresight_test_cpuid(struct coresight_device *csdev)
+{
+	return 0;
+}
+
+static void test_default_sink(struct kunit *test)
+{
+	/*
+	 * ETM -> ETF -> ETR -> CATU
+	 *                ^
+	 *                | default
+	 */
+	struct device *dev = kunit_device_register(test, "coresight_kunit");
+	struct coresight_device *etm = coresight_test_device(dev),
+				*etf = coresight_test_device(dev),
+				*etr = coresight_test_device(dev),
+				*catu = coresight_test_device(dev);
+	struct coresight_connection conn = {};
+	struct coresight_ops_source src_ops = {.cpu_id = coresight_test_cpuid };
+	struct coresight_ops etm_cs_ops = { .source_ops	= &src_ops };
+
+	etm->type = CORESIGHT_DEV_TYPE_SOURCE;
+	etm->ops = &etm_cs_ops;
+	etf->type = CORESIGHT_DEV_TYPE_LINKSINK;
+	etf->subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
+	etr->type = CORESIGHT_DEV_TYPE_SINK;
+	etr->subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM;
+	catu->type = CORESIGHT_DEV_TYPE_HELPER;
+
+	conn.src_dev = etm;
+	conn.dest_dev = etf;
+	coresight_add_out_conn(dev, etm->pdata, &conn);
+
+	conn.src_dev = etf;
+	conn.dest_dev = etr;
+	coresight_add_out_conn(dev, etf->pdata, &conn);
+
+	conn.src_dev = etr;
+	conn.dest_dev = catu;
+	coresight_add_out_conn(dev, etr->pdata, &conn);
+
+	KUNIT_ASSERT_PTR_EQ(test, coresight_find_default_sink(etm), etr);
+}
+
+static struct kunit_case coresight_testcases[] = {
+	KUNIT_CASE(test_default_sink),
+	{}
+};
+
+static struct kunit_suite coresight_test_suite = {
+	.name = "coresight_test_suite",
+	.test_cases = coresight_testcases,
+};
+
+kunit_test_suites(&coresight_test_suite);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("James Clark <james.clark@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Arm CoreSight KUnit tests");

---
base-commit: eeafe6a8790ea125252ca2e23c1a2469eaff1d9a
change-id: 20250305-james-cs-kunit-test-3af1df2401e6

Best regards,
-- 
James Clark <james.clark@xxxxxxxxxx>