drm/amd/display: Add subconnector property tests for connector

Add KUnit coverage for update_subconnector_property() on the
amdgpu_dm_connector suite:

- DP connector with a sink: subconnector property is resolved from
  the dongle type (VGA converter -> VGA).
- DP connector without a sink: dongle type is ignored and the
  property stays Unknown.
- Non-DP connector: function early-returns and leaves a pre-seeded
  property value untouched.

Assisted-by: Copilot:Claude-Opus-4.8
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Signed-off-by: George Zhang <george.zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 145 insertions, 1 deletions

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
index 1a1c3642c456..b24a4afb9153 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
@@ -235,7 +235,7 @@ STATIC_IFN_KUNIT enum drm_mode_subconnector get_subconnector_type(struct dc_link
 }
 EXPORT_IF_KUNIT(get_subconnector_type);
 
-static void update_subconnector_property(struct amdgpu_dm_connector *aconnector)
+STATIC_IFN_KUNIT void update_subconnector_property(struct amdgpu_dm_connector *aconnector)
 {
 	struct dc_link *link = aconnector->dc_link;
 	struct drm_connector *connector = &aconnector->base;
@@ -251,6 +251,7 @@ static void update_subconnector_property(struct amdgpu_dm_connector *aconnector)
 			connector->dev->mode_config.dp_subconnector_property,
 			subconnector);
 }
+EXPORT_IF_KUNIT(update_subconnector_property);
 
 static int amdgpu_dm_connector_get_modes(struct drm_connector *connector);
 
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.h
index ca0fdb0dc41a..ecf23d0fb72e 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.h
@@ -147,6 +147,7 @@ int amdgpu_dm_encoder_init(struct drm_device *dev,
 
 #if IS_ENABLED(CONFIG_DRM_AMD_DC_KUNIT_TEST)
 enum drm_mode_subconnector get_subconnector_type(struct dc_link *link);
+void update_subconnector_property(struct amdgpu_dm_connector *aconnector);
 enum display_content_type
 get_output_content_type(const struct drm_connector_state *connector_state);
 bool adjust_colour_depth_from_display_info(struct dc_crtc_timing *timing_out,
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_connector_test.c b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_connector_test.c
index 91f9543dd7bb..782a22e4f074 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_connector_test.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_connector_test.c
@@ -2527,6 +2527,144 @@ static void dm_test_set_panel_type_defaults_to_lcd(struct kunit *test)
 			(int)PANEL_TYPE_LCD);
 }
 
+/* Tests for update_subconnector_property() */
+
+/**
+ * dm_test_update_subconnector_dp_with_sink - Test subconnector property is set
+ * from the dongle type for a DisplayPort connector with a sink
+ * @test: The KUnit test context
+ */
+static void dm_test_update_subconnector_dp_with_sink(struct kunit *test)
+{
+	struct device *dev;
+	struct drm_device *drm;
+	struct amdgpu_dm_connector *aconnector;
+	struct dc_link *link;
+	uint64_t val = 0;
+
+	dev = drm_kunit_helper_alloc_device(test);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	drm = __drm_kunit_helper_alloc_drm_device(test, dev,
+						   sizeof(*drm), 0,
+						   DRIVER_MODESET);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
+
+	aconnector = kunit_kzalloc(test, sizeof(*aconnector), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, aconnector);
+	link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, link);
+
+	drmm_connector_init(drm, &aconnector->base, &dm_test_connector_funcs,
+			    DRM_MODE_CONNECTOR_DisplayPort, NULL);
+	drm_connector_attach_dp_subconnector_property(&aconnector->base);
+
+	link->dpcd_caps.dongle_type = DISPLAY_DONGLE_DP_VGA_CONVERTER;
+	aconnector->dc_link = link;
+	/* Any non-NULL sink enables dongle-type resolution */
+	aconnector->dc_sink = kunit_kzalloc(test, sizeof(*aconnector->dc_sink), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, aconnector->dc_sink);
+
+	update_subconnector_property(aconnector);
+
+	KUNIT_EXPECT_EQ(test, drm_object_property_get_value(&aconnector->base.base,
+				aconnector->base.dev->mode_config.dp_subconnector_property,
+				&val), 0);
+	KUNIT_EXPECT_EQ(test, (int)val, (int)DRM_MODE_SUBCONNECTOR_VGA);
+}
+
+/**
+ * dm_test_update_subconnector_dp_no_sink - Test subconnector property stays
+ * unknown for a DisplayPort connector without a sink
+ * @test: The KUnit test context
+ */
+static void dm_test_update_subconnector_dp_no_sink(struct kunit *test)
+{
+	struct device *dev;
+	struct drm_device *drm;
+	struct amdgpu_dm_connector *aconnector;
+	struct dc_link *link;
+	uint64_t val = 0;
+
+	dev = drm_kunit_helper_alloc_device(test);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	drm = __drm_kunit_helper_alloc_drm_device(test, dev,
+						   sizeof(*drm), 0,
+						   DRIVER_MODESET);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
+
+	aconnector = kunit_kzalloc(test, sizeof(*aconnector), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, aconnector);
+	link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, link);
+
+	drmm_connector_init(drm, &aconnector->base, &dm_test_connector_funcs,
+			    DRM_MODE_CONNECTOR_DisplayPort, NULL);
+	drm_connector_attach_dp_subconnector_property(&aconnector->base);
+
+	/* Dongle type is set, but no sink means it must not be consulted */
+	link->dpcd_caps.dongle_type = DISPLAY_DONGLE_DP_HDMI_CONVERTER;
+	aconnector->dc_link = link;
+	aconnector->dc_sink = NULL;
+
+	update_subconnector_property(aconnector);
+
+	KUNIT_EXPECT_EQ(test, drm_object_property_get_value(&aconnector->base.base,
+				aconnector->base.dev->mode_config.dp_subconnector_property,
+				&val), 0);
+	KUNIT_EXPECT_EQ(test, (int)val, (int)DRM_MODE_SUBCONNECTOR_Unknown);
+}
+
+/**
+ * dm_test_update_subconnector_non_dp_noop - Test non-DisplayPort connector is
+ * left untouched (early return)
+ * @test: The KUnit test context
+ */
+static void dm_test_update_subconnector_non_dp_noop(struct kunit *test)
+{
+	struct device *dev;
+	struct drm_device *drm;
+	struct amdgpu_dm_connector *aconnector;
+	struct dc_link *link;
+	uint64_t val = 0;
+
+	dev = drm_kunit_helper_alloc_device(test);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	drm = __drm_kunit_helper_alloc_drm_device(test, dev,
+						   sizeof(*drm), 0,
+						   DRIVER_MODESET);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
+
+	aconnector = kunit_kzalloc(test, sizeof(*aconnector), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, aconnector);
+	link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, link);
+
+	drmm_connector_init(drm, &aconnector->base, &dm_test_connector_funcs,
+			    DRM_MODE_CONNECTOR_HDMIA, NULL);
+	drm_connector_attach_dp_subconnector_property(&aconnector->base);
+
+	/* Pre-seed the property to a non-default value */
+	drm_object_property_set_value(&aconnector->base.base,
+			aconnector->base.dev->mode_config.dp_subconnector_property,
+			DRM_MODE_SUBCONNECTOR_VGA);
+
+	link->dpcd_caps.dongle_type = DISPLAY_DONGLE_DP_HDMI_CONVERTER;
+	aconnector->dc_link = link;
+	aconnector->dc_sink = kunit_kzalloc(test, sizeof(*aconnector->dc_sink), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, aconnector->dc_sink);
+
+	update_subconnector_property(aconnector);
+
+	/* Non-DP connector: value must remain what we seeded */
+	KUNIT_EXPECT_EQ(test, drm_object_property_get_value(&aconnector->base.base,
+				aconnector->base.dev->mode_config.dp_subconnector_property,
+				&val), 0);
+	KUNIT_EXPECT_EQ(test, (int)val, (int)DRM_MODE_SUBCONNECTOR_VGA);
+}
+
 static struct kunit_case amdgpu_dm_connector_tests[] = {
 	/* get_subconnector_type */
 	KUNIT_CASE(dm_test_subconnector_type_none),
@@ -2664,6 +2802,10 @@ static struct kunit_case amdgpu_dm_connector_tests[] = {
 	KUNIT_CASE(dm_test_is_freesync_video_mode_null_mode),
 	KUNIT_CASE(dm_test_is_freesync_video_mode_match),
 	KUNIT_CASE(dm_test_is_freesync_video_mode_no_match),
+	/* update_subconnector_property */
+	KUNIT_CASE(dm_test_update_subconnector_dp_with_sink),
+	KUNIT_CASE(dm_test_update_subconnector_dp_no_sink),
+	KUNIT_CASE(dm_test_update_subconnector_non_dp_noop),
 	/* amdgpu_dm_update_cacp_caps */
 	KUNIT_CASE(dm_test_cacp_caps_unsupported_ip),
 	KUNIT_CASE(dm_test_cacp_caps_excluded_ip_316),