From: Bhawanpreet Lakha <[email protected]> Add a KUnit test for amdgpu_dm_detect_mst_link_for_all_connectors() where an MST branch fails to start its topology manager. A powered-down aux forces drm_dp_mst_topology_mgr_set_mst() to fail on its initial DPCD read, exercising the error path that downgrades the link and stops the manager.
Assisted-by: Copilot:Claude-Opus-4.8 Reviewed-by: Alex Hung <[email protected]> Signed-off-by: Bhawanpreet Lakha <[email protected]> Signed-off-by: Ivan Lipski <[email protected]> --- .../tests/amdgpu_dm_connector_test.c | 49 +++++++++++++++++++ 1 file changed, 49 insertions(+) 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 b51aba8c07c3c..14240e6485049 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 @@ -2906,6 +2906,54 @@ static void dm_test_detect_mst_branch_without_aux(struct kunit *test) amdgpu_dm_detect_mst_link_for_all_connectors(drm), 0); } +/** + * dm_test_detect_mst_start_fail - Test the MST-start failure path + * @test: The KUnit test context + * + * An MST branch whose topology manager fails to start must downgrade the link + * to a single connection and attempt to stop the topology manager. The failure + * is forced by giving the manager a powered-down aux, so its initial DPCD read + * returns an error before any real transfer is attempted. + */ +static void dm_test_detect_mst_start_fail(struct kunit *test) +{ + struct drm_device *drm = dm_test_alloc_drm(test); + struct amdgpu_dm_connector *aconnector; + struct dc_link *link; + struct drm_dp_aux *aux; + + aconnector = dm_test_add_connector(test, drm, + DRM_MODE_CONNECTOR_DisplayPort); + link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, link); + aux = kunit_kzalloc(test, sizeof(*aux), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, aux); + + link->type = dc_connection_mst_branch; + aconnector->dc_link = link; + + /* + * A powered-down aux makes the initial DPCD read return -EBUSY before + * any transfer, so drm_dp_mst_topology_mgr_set_mst() fails fast. + */ + mutex_init(&aux->hw_mutex); + aux->name = "kunit-mst-aux"; + aux->powered_down = true; + mutex_init(&aconnector->mst_mgr.lock); + aconnector->mst_mgr.dev = drm; + aconnector->mst_mgr.aux = aux; + + /* + * link->priv is left NULL so dm_helpers_dp_mst_stop_top_mgr() returns + * early without recursing back into the topology manager. + */ + KUNIT_EXPECT_EQ(test, + amdgpu_dm_detect_mst_link_for_all_connectors(drm), 0); + + /* The failure path downgrades the link to a single connection. */ + KUNIT_EXPECT_EQ(test, link->type, dc_connection_single); +} + /* Tests for amdgpu_dm_find_first_crtc_matching_connector() */ /* @@ -5835,6 +5883,7 @@ static struct kunit_case amdgpu_dm_connector_tests[] = { KUNIT_CASE(dm_test_detect_mst_skips_writeback), KUNIT_CASE(dm_test_detect_mst_non_mst_link), KUNIT_CASE(dm_test_detect_mst_branch_without_aux), + KUNIT_CASE(dm_test_detect_mst_start_fail), /* amdgpu_dm_find_first_crtc_matching_connector */ KUNIT_CASE(dm_test_find_first_crtc_match), KUNIT_CASE(dm_test_find_first_crtc_no_match), -- 2.43.0
