[PATCH i-g-t 05/14] lib/igt_kms: add function to force link training failure

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

i915_dp_force_link_training_failure debugfs
file is used to force link training failure.
add a function to force link training failure.

Signed-off-by: Kunal Joshi <kunal1.joshi@intel.com>
---
 lib/igt_kms.c | 26 ++++++++++++++++++++++++++
 lib/igt_kms.h |  1 +
 2 files changed, 27 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 553a08f2f..683989e84 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -6843,3 +6843,29 @@ void igt_force_link_retrain(int drm_fd, igt_output_t *output, int retrain_count)
 	igt_sysfs_write(dir, "i915_dp_force_link_retrain", value, sizeof(value));
 	close(dir);
 }
+
+/**
+ * igt_force_lt_failure:
+ * @drm_fd: A drm file descriptor
+ * @output: Target output
+ * @failure_count: 1 for same link param and
+ *                2 for reduced link params
+ *
+ * Force link training failure on the output.
+ * @failure_count: 1 for retraining with same link params
+ * 				   2 for retraining with reduced link params
+ */
+void igt_force_lt_failure(int drm_fd, igt_output_t *output, int failure_count)
+{
+	int dir;
+	char value[2];
+
+	snprintf(value, sizeof(value), "%d", failure_count);
+	igt_require_f(output->name, "Invalid output");
+	dir = igt_debugfs_connector_dir(drm_fd, output->name, O_RDONLY);
+	igt_assert_f(dir >= 0, "Failed to open debugfs dir for connector %s\n",
+			       igt_output_name(output));
+	igt_sysfs_write(dir, "i915_dp_force_link_training_failure",
+			     value, sizeof(value));
+	close(dir);
+}
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 9ba8c6394..57829416a 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1252,5 +1252,6 @@ enum dp_lane_count igt_get_dp_lane_count_set_for_output(int drm_fd, igt_output_t
 enum dp_link_rate igt_get_dp_max_link_rate(int drm_fd, igt_output_t *output);
 enum dp_lane_count igt_get_dp_max_lane_count(int drm_fd, igt_output_t *output);
 void igt_force_link_retrain(int drm_fd, igt_output_t *output, int retrain_count);
+void igt_force_lt_failure(int drm_fd, igt_output_t *output, int failure_count);
 
 #endif /* __IGT_KMS_H__ */
-- 
2.34.1