[PATCH i-g-t 04/14] lib/igt_kms: add function to force link retrain

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

i915_dp_force_link_retrain debugfs allow forcing retraing
on the connector. add a helper to write given retraining count
to the same.

Signed-off-by: Kunal Joshi <kunal1.joshi@intel.com>
---
 lib/igt_kms.c | 22 ++++++++++++++++++++++
 lib/igt_kms.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 21ea8550c..553a08f2f 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -6821,3 +6821,25 @@ enum dp_lane_count igt_get_dp_max_lane_count(int drm_fd, igt_output_t *output)
 
 	return max_lane_count;
 }
+
+/**
+ * igt_force_link_retrain:
+ * @drm_fd: A drm file descriptor
+ * @output: Target output
+ * @retrain_count: number of retraining required
+ *
+ * Force link retrain on the output.
+ */
+void igt_force_link_retrain(int drm_fd, igt_output_t *output, int retrain_count)
+{
+	int dir;
+	char value[2];
+
+	snprintf(value, sizeof(value), "%d", retrain_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_retrain", value, sizeof(value));
+	close(dir);
+}
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 1d3226c5c..9ba8c6394 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1251,5 +1251,6 @@ enum dp_link_rate igt_get_dp_link_rate_set_for_output(int drm_fd, igt_output_t *
 enum dp_lane_count igt_get_dp_lane_count_set_for_output(int drm_fd, igt_output_t *output);
 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);
 
 #endif /* __IGT_KMS_H__ */
-- 
2.43.0