[PATCH i-g-t] tests/kms_display_modes: Fit modes within MST bandwidth constraints

[Jeevan B]

Instead of checking only the current modes, find a combination of
modes in the MST topology that can be accommodated within the
available link bandwidth.

Fixes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/1542
Signed-off-by: Jeevan B <jeevan.b at intel.com>
---
 tests/kms_display_modes.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/kms_display_modes.c b/tests/kms_display_modes.c
index 588820170..d1083f470 100644
--- a/tests/kms_display_modes.c
+++ b/tests/kms_display_modes.c
@@ -49,6 +49,22 @@ typedef struct {
 	int n_pipes;
 } data_t;
 
+static bool fit_modes_in_bw(data_t *data)
+{
+	bool found;
+	int ret;
+
+	ret = igt_display_try_commit_atomic(&data->display,
+					    DRM_MODE_ATOMIC_TEST_ONLY |
+					    DRM_MODE_ATOMIC_ALLOW_MODESET, NULL);
+	if (ret != 0) {
+		found = igt_override_all_active_output_modes_to_fit_bw(&data->display);
+		igt_require_f(found,
+			      "No valid mode combo found for modeset\n");
+	}
+	return true;
+}
+
 static bool output_is_dp_mst(data_t *data, igt_output_t *output, int i)
 {
 	int connector_id;
@@ -93,6 +109,8 @@ static void run_extendedmode_basic(data_t *data,
 	mode[0] = igt_output_get_mode(output1);
 	mode[1] = igt_output_get_mode(output2);
 
+	igt_assert(fit_modes_in_bw(data));
+
 	pipe_crc[0] = igt_pipe_crc_new(data->drm_fd, pipe1, IGT_PIPE_CRC_SOURCE_AUTO);
 	pipe_crc[1] = igt_pipe_crc_new(data->drm_fd, pipe2, IGT_PIPE_CRC_SOURCE_AUTO);
 
@@ -138,6 +156,7 @@ static void run_extendedmode_basic(data_t *data,
 	igt_fb_set_size(&fb, plane[1], mode[1]->hdisplay, mode[1]->vdisplay);
 	igt_plane_set_size(plane[1], mode[1]->hdisplay, mode[1]->vdisplay);
 
+	igt_assert(fit_modes_in_bw(data));
 	igt_display_commit2(display, COMMIT_ATOMIC);
 
 	igt_pipe_crc_collect_crc(pipe_crc[0], &crc[0]);
@@ -158,6 +177,7 @@ static void run_extendedmode_basic(data_t *data,
 			  DRM_PLANE_TYPE_PRIMARY), NULL);
 	igt_plane_set_fb(igt_pipe_get_plane_type(&display->pipes[pipe2],
 			  DRM_PLANE_TYPE_PRIMARY), NULL);
+	igt_assert(fit_modes_in_bw(data));
 	igt_display_commit2(display, COMMIT_ATOMIC);
 
 	/*Compare CRC*/
-- 
2.25.1