[PATCH 38/59] drm/amd/display: Test link and sink dump

[WHAT]
Add KUnit tests for amdgpu_dm_dump_links_and_sinks() covering a device
without DC, a DC without links, named local and remote sinks, and missing
or unnamed sinks.

[HOW]
Build lightweight DC link and sink objects so the dump walks each naming
and skip path without display hardware.

Assisted-by: Copilot:Claude-Opus-5 GPT-5.6-Sol
Reviewed-by: Bhawanpreet Lakha <[email protected]>
Signed-off-by: Alex Hung <[email protected]>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  3 +-
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |  1 +
 .../display/amdgpu_dm/tests/amdgpu_dm_test.c  | 92 +++++++++++++++++++
 3 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 8db18d7cf49f..fc03fcca4c6a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1776,7 +1776,7 @@ EXPORT_IF_KUNIT(amdgpu_dm_apply_delay_after_dpcd_poweroff);
  * (MST) sinks. Should be called after connector detection is complete to see
  * the final state of all links.
  */
-static void amdgpu_dm_dump_links_and_sinks(struct amdgpu_device *adev)
+STATIC_IFN_KUNIT void amdgpu_dm_dump_links_and_sinks(struct amdgpu_device *adev)
 {
 	struct dc *dc = adev->dm.dc;
 	struct drm_device *dev = adev_to_drm(adev);
@@ -1828,6 +1828,7 @@ static void amdgpu_dm_dump_links_and_sinks(struct amdgpu_device *adev)
 		}
 	}
 }
+EXPORT_IF_KUNIT(amdgpu_dm_dump_links_and_sinks);
 
 static int dm_resume(struct amdgpu_ip_block *ip_block)
 {
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index 0151913336b7..7cb22915d18b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -1201,6 +1201,7 @@ int add_affected_mst_dsc_crtcs(struct drm_atomic_commit *state,
 bool amdgpu_dm_crtc_mem_type_changed(struct drm_device *dev,
 				     struct drm_atomic_commit *state,
 				     struct drm_crtc_state *crtc_state);
+void amdgpu_dm_dump_links_and_sinks(struct amdgpu_device *adev);
 int dm_plane_layer_index_cmp(const void *a, const void *b);
 int fill_plane_color_attributes(const struct drm_plane_state *plane_state,
 				const enum surface_pixel_format format,
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_test.c b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_test.c
index 799cd3867a77..63d43f917273 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_test.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_test.c
@@ -2759,6 +2759,93 @@ static void dm_test_reset_plane_other_modifier(struct kunit *test)
 	KUNIT_EXPECT_TRUE(test, dm_test_should_reset_plane(ctx));
 }
 
+/* Tests for amdgpu_dm_dump_links_and_sinks() */
+
+/**
+ * dm_test_dump_links_no_dc - Test a device without DC dumps nothing
+ * @test: The KUnit test context
+ */
+static void dm_test_dump_links_no_dc(struct kunit *test)
+{
+	struct amdgpu_device *adev = dm_kunit_alloc_adev(test);
+
+	amdgpu_dm_dump_links_and_sinks(adev);
+}
+
+/**
+ * dm_test_dump_links_no_links - Test a DC without links dumps nothing
+ * @test: The KUnit test context
+ */
+static void dm_test_dump_links_no_links(struct kunit *test)
+{
+	struct amdgpu_device *adev = dm_kunit_alloc_adev(test);
+
+	adev->dm.dc = dm_kunit_alloc_dc_with_ctx(test);
+
+	amdgpu_dm_dump_links_and_sinks(adev);
+}
+
+/*
+ * Attach a single DC link to @adev so amdgpu_dm_dump_links_and_sinks() walks it.
+ */
+static struct dc_link *dm_test_dc_with_link(struct kunit *test,
+					   struct amdgpu_device *adev)
+{
+	struct dc *dc = dm_kunit_alloc_dc_with_ctx(test);
+	struct dc_link *link = dm_kunit_alloc_link(test);
+
+	dc->links[0] = link;
+	dc->link_count = 1;
+	adev->dm.dc = dc;
+
+	return link;
+}
+
+/**
+ * dm_test_dump_links_with_sinks - Test local and remote sinks are walked
+ * @test: The KUnit test context
+ */
+static void dm_test_dump_links_with_sinks(struct kunit *test)
+{
+	struct amdgpu_device *adev = dm_kunit_alloc_adev(test);
+	struct dc_link *link = dm_test_dc_with_link(test, adev);
+	struct dc_sink *local_sink, *remote_sink;
+
+	local_sink = kunit_kzalloc(test, sizeof(*local_sink), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, local_sink);
+	remote_sink = kunit_kzalloc(test, sizeof(*remote_sink), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, remote_sink);
+
+	strscpy(local_sink->edid_caps.display_name, "local");
+	strscpy(remote_sink->edid_caps.display_name, "remote");
+	link->local_sink = local_sink;
+	link->sink_count = 1;
+	link->remote_sinks[0] = remote_sink;
+	adev->dm.dc->link_count = 2;
+
+	amdgpu_dm_dump_links_and_sinks(adev);
+}
+
+/**
+ * dm_test_dump_links_unnamed_sinks - Test links without a sink or EDID name
+ * @test: The KUnit test context
+ */
+static void dm_test_dump_links_unnamed_sinks(struct kunit *test)
+{
+	struct amdgpu_device *adev = dm_kunit_alloc_adev(test);
+	struct dc_link *link = dm_test_dc_with_link(test, adev);
+	struct dc_sink *remote_sink;
+
+	remote_sink = kunit_kzalloc(test, sizeof(*remote_sink), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, remote_sink);
+
+	link->sink_count = 2;
+	link->remote_sinks[0] = NULL;
+	link->remote_sinks[1] = remote_sink;
+
+	amdgpu_dm_dump_links_and_sinks(adev);
+}
+
 static struct kunit_case amdgpu_dm_tests[] = {
 	/* Simple DM callbacks */
 	KUNIT_CASE(dm_test_wait_for_idle),
@@ -2896,6 +2983,11 @@ static struct kunit_case amdgpu_dm_tests[] = {
 	KUNIT_CASE(dm_test_reset_plane_other_no_fb),
 	KUNIT_CASE(dm_test_reset_plane_other_format),
 	KUNIT_CASE(dm_test_reset_plane_other_modifier),
+	/* amdgpu_dm_dump_links_and_sinks */
+	KUNIT_CASE(dm_test_dump_links_no_dc),
+	KUNIT_CASE(dm_test_dump_links_no_links),
+	KUNIT_CASE(dm_test_dump_links_with_sinks),
+	KUNIT_CASE(dm_test_dump_links_unnamed_sinks),
 	{}
 };
 
-- 
2.43.0