[PATCH i-g-t 08/13] tests/intel/kms_dp_link_training: log the DP link inventory

[Kunal Joshi <kunal1.joshi@intel.com>]

When a subtest skips, there's no telling from the log whether the
monitor or the dock is missing, or the link just doesn't allow any
suitable configs.

Log each connected DP output once in the fixture, with SST/MST, the
Type-C port mode, and the allowed link configs:

	DP-2: MST, tbt-alt, pin assignment D, TC max lanes 4
	DP-2: allowed configs: 4x2000000 4x1000000 4x810000 2x810000

This is just logging, with no functional changes.

Assisted-by: GitHub_Copilot:claude-opus-5
Signed-off-by: Kunal Joshi <kunal1.joshi@intel.com>
Reviewed-by: Sowmiya S <sowmiya.s@intel.com>
---
 tests/intel/kms_dp_link_training.c | 68 ++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/tests/intel/kms_dp_link_training.c b/tests/intel/kms_dp_link_training.c
index 7125bd033..9105570d1 100644
--- a/tests/intel/kms_dp_link_training.c
+++ b/tests/intel/kms_dp_link_training.c
@@ -290,6 +290,71 @@ static void train_link_config(data_t *data, bool mst,
 	assert_link_retrain_not_disabled(data, config);
 }
 
+/*
+ * log_link_inventory - Describe every connected DP link once.
+ *
+ * With the configuration in the subtest name, most subtests skip on any one
+ * machine. This is what tells a missing monitor apart from a monitor behind a
+ * dock that offers no UHBR configuration, without having to re-run by hand.
+ */
+static void log_link_inventory(data_t *data)
+{
+	igt_output_t *output;
+
+	for_each_connected_output(&data->display, output) {
+		struct i915_dp_link_config configs[MAX_LINK_CONFIGS];
+		enum i915_dp_tc_mode tc_mode;
+		char configs_str[512];
+		char pin_assignment;
+		int tc_max_lanes;
+		int num_configs;
+		int len = 0;
+		int i;
+
+		if (output->config.connector->connector_type !=
+		    DRM_MODE_CONNECTOR_DisplayPort)
+			continue;
+
+		tc_mode = i915_dp_get_tc_mode(data->drm_fd, output,
+					      &pin_assignment, &tc_max_lanes);
+
+		if (tc_mode == I915_DP_TC_NONE)
+			igt_info("%s: %s, %s\n", igt_output_name(output),
+				 igt_check_output_is_dp_mst(output) ? "MST" : "SST",
+				 i915_dp_tc_mode_name(tc_mode));
+		else
+			igt_info("%s: %s, %s, pin assignment %c, TC max lanes %d\n",
+				 igt_output_name(output),
+				 igt_check_output_is_dp_mst(output) ? "MST" : "SST",
+				 i915_dp_tc_mode_name(tc_mode),
+				 pin_assignment, tc_max_lanes);
+
+		if (!i915_dp_has_allowed_link_configs_debugfs(data->drm_fd, output)) {
+			igt_info("%s: no allowed link configs debugfs\n",
+				 igt_output_name(output));
+			continue;
+		}
+
+		/*
+		 * Enumerate with the forced parameters reset, or the set read
+		 * back is the forced one rather than the real one.
+		 */
+		i915_dp_reset_link_params(data->drm_fd, output);
+
+		num_configs = i915_dp_get_allowed_link_configs(data->drm_fd, output,
+							       configs,
+							       ARRAY_SIZE(configs));
+
+		for (i = 0; i < num_configs && len < (int)sizeof(configs_str); i++)
+			len += snprintf(configs_str + len, sizeof(configs_str) - len,
+					" %dx%d", configs[i].lane_count,
+					configs[i].link_rate);
+
+		igt_info("%s: allowed configs:%s\n", igt_output_name(output),
+			 num_configs ? configs_str : " none");
+	}
+}
+
 /*
  * override_lowest_mode - Drive the mode with the lowest pixel clock, so that
  * the largest number of link configurations can carry it.
@@ -527,6 +592,9 @@ int igt_main()
 		 */
 		igt_assert_f(igt_ignore_long_hpd(data.drm_fd, false),
 			     "Unable to disable ignore long hpd\n");
+
+		if (is_intel_device(data.drm_fd))
+			log_link_inventory(&data);
 	}
 
 	igt_describe("Test we can drive UHBR rates over SST");
-- 
2.25.1