[PATCH 73/82] drm/amd/display: Cover add_fs_modes illegal timing skip

From: Bhawanpreet Lakha <[email protected]>

Add a KUnit test for add_fs_modes() confirming that a generated mode
with illegal timing is skipped rather than added.

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          | 21 +++++++++++++++++++
 1 file changed, 21 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 988f0885679aa..5e5c372e9e01e 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
@@ -5664,6 +5664,26 @@ static void dm_test_add_fs_modes_out_of_range(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, (int)add_fs_modes(aconnector), 0);
 }
 
+/**
+ * dm_test_add_fs_modes_skips_illegal - Test illegal derived timings are dropped
+ * @test: The KUnit test context
+ *
+ * A reference vtotal of 1133 gives a true refresh of ~59.58 that rounds up to
+ * 60, so the 60000 rate clears the refresh check yet yields a negative vtotal
+ * delta. The resulting timing is illegal, so add_fs_modes() skips it and
+ * returns 0.
+ */
+static void dm_test_add_fs_modes_skips_illegal(struct kunit *test)
+{
+	struct amdgpu_dm_connector *aconnector = dm_test_fs_setup(test);
+
+	aconnector->freesync_vid_base.vtotal = 1133;
+	aconnector->min_vfreq = 59;
+	aconnector->max_vfreq = 60;
+
+	KUNIT_EXPECT_EQ(test, (int)add_fs_modes(aconnector), 0);
+}
+
 /**
  * dm_test_add_freesync_modes_null_edid_noop - Test NULL EDID adds no modes
  * @test: The KUnit test context
@@ -8270,6 +8290,7 @@ static struct kunit_case amdgpu_dm_connector_tests[] = {
 	KUNIT_CASE(dm_test_add_fs_modes_no_preferred_mode),
 	KUNIT_CASE(dm_test_add_fs_modes_generates),
 	KUNIT_CASE(dm_test_add_fs_modes_out_of_range),
+	KUNIT_CASE(dm_test_add_fs_modes_skips_illegal),
 	/* amdgpu_dm_connector_add_freesync_modes */
 	KUNIT_CASE(dm_test_add_freesync_modes_null_edid_noop),
 	/* amdgpu_dm_i2c_func */
-- 
2.43.0