[PATCH i-g-t 3/4] lib/igt_kms: add function to set link params

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

add function to force link rate and lane count
for given output, install exit handle to set auto
at exit

Signed-off-by: Kunal Joshi <kunal1.joshi@intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
---
 lib/igt_kms.c | 33 +++++++++++++++++++++++++++++++++
 lib/igt_kms.h |  2 ++
 2 files changed, 35 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 0ba1afb08..bc46487c5 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -7269,6 +7269,39 @@ void igt_reset_link_params(int drm_fd, igt_output_t *output)
 	drmModeFreeConnector(temp);
 }
 
+/**
+ * igt_set_link_params:
+ * @drm_fd: A drm file descriptor
+ * @output: Target output
+ *
+ * set link rate and lane count to given value, also installs exit handler
+ * to set link rate and lane count to auto on exit
+ */
+void igt_set_link_params(int drm_fd, igt_output_t *output,
+			   char *link_rate, char *lane_count)
+{
+	bool valid;
+	drmModeConnector *temp;
+
+	valid = true;
+	valid = valid && connector_attr_set_debugfs(drm_fd, output->config.connector,
+						    "i915_dp_force_link_rate",
+						    link_rate, "auto", true);
+	valid = valid && connector_attr_set_debugfs(drm_fd, output->config.connector,
+						    "i915_dp_force_lane_count",
+						    lane_count, "auto", true);
+	igt_assert_f(valid, "Unable to set attr or install exit handler\n");
+	dump_connector_attrs();
+	igt_install_exit_handler(reset_connectors_at_exit);
+
+	/*
+	 * To allow callers to always use GetConnectorCurrent we need to force a
+	 * redetection here.
+	 */
+	temp = drmModeGetConnector(drm_fd, output->config.connector->connector_id);
+	drmModeFreeConnector(temp);
+}
+
 /**
  * igt_backlight_read:
  * @result:	Pointer to store the result
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index 7227f0b0e..31b9820cb 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1271,6 +1271,8 @@ bool igt_has_force_link_training_failure_debugfs(int drmfd, igt_output_t *output
 int igt_get_dp_pending_lt_failures(int drm_fd, igt_output_t *output);
 int igt_get_dp_pending_retrain(int drm_fd, igt_output_t *output);
 void igt_reset_link_params(int drm_fd, igt_output_t *output);
+void igt_set_link_params(int drm_fd, igt_output_t *output,
+			   char *link_rate, char *lane_count);
 int igt_backlight_read(int *result, const char *fname, igt_backlight_context_t *context);
 int igt_backlight_write(int value, const char *fname, igt_backlight_context_t *context);
 
-- 
2.25.1