[PATCH 18/20] drm/i915/dp: Add debugfs entry to force link training failure

[Imre Deak]

Add a connector debugfs entry to force a failure during the following
1-2 link training. The entry will auto-reset after the specified link
training events are complete.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 .../drm/i915/display/intel_display_debugfs.c  | 47 +++++++++++++++++++
 .../drm/i915/display/intel_display_types.h    |  1 +
 .../drm/i915/display/intel_dp_link_training.c |  5 +-
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
index 521721a20358f..098d0f5190723 100644
--- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
+++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
@@ -1525,6 +1525,50 @@ static ssize_t i915_dp_requested_lane_count_write(struct file *file,
 }
 DEFINE_SHOW_STORE_ATTRIBUTE(i915_dp_requested_lane_count);
 
+static int i915_dp_force_link_training_failure_show(void *data, u64 *val)
+{
+	struct intel_connector *connector = to_intel_connector(data);
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
+	struct intel_dp *intel_dp;
+	int err;
+
+	err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+	if (err)
+		return err;
+
+	intel_dp = intel_connector_to_intel_dp(connector);
+	*val = intel_dp->link_train.force_failure;
+
+	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+	return 0;
+}
+
+static int i915_dp_force_link_training_failure_write(void *data, u64 val)
+{
+	struct intel_connector *connector = to_intel_connector(data);
+	struct drm_i915_private *i915 = to_i915(connector->base.dev);
+	struct intel_dp *intel_dp;
+	int err;
+
+	if (val > 2)
+		return -EINVAL;
+
+	err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+	if (err)
+		return err;
+
+	intel_dp = intel_connector_to_intel_dp(connector);
+	intel_dp->link_train.force_failure = val;
+
+	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(i915_dp_force_link_training_failure_fops,
+			 i915_dp_force_link_training_failure_show,
+			 i915_dp_force_link_training_failure_write, "%llu\n");
+
 static int i915_dsc_output_format_show(struct seq_file *m, void *data)
 {
 	struct intel_connector *connector = m->private;
@@ -1739,6 +1783,9 @@ void intel_connector_debugfs_add(struct intel_connector *connector)
 
 		debugfs_create_file("i915_dp_lane_count", 0644, root,
 				    connector, &i915_dp_requested_lane_count_fops);
+
+		debugfs_create_file("i915_dp_force_link_training_failure", 0644, root,
+				    connector, &i915_dp_force_link_training_failure_fops);
 	}
 
 	if (DISPLAY_VER(i915) >= 11 &&
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 351c445d3cb5b..62acec5236052 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1768,6 +1768,7 @@ struct intel_dp {
 		bool retrain_disabled;
 		/* Sequential failures after a passing LT */
 		int seq_failures;
+		int force_failure;
 	} link_train;
 	bool reset_link_params;
 	int mso_link_count;
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 352c77f46015e..c260299c53b7c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -1484,7 +1484,10 @@ void intel_dp_start_link_train(struct intel_dp *intel_dp,
 	else
 		passed = intel_dp_link_train_all_phys(intel_dp, crtc_state, lttpr_count);
 
-	if (passed) {
+	if (intel_dp->link_train.force_failure) {
+		intel_dp->link_train.force_failure--;
+		lt_dbg(intel_dp, DP_PHY_DPRX, "Forcing link training failure\n");
+	} else if (passed) {
 		intel_dp->link_train.seq_failures = 0;
 		intel_dp_queue_link_check(intel_dp, 2000);
 		return;
-- 
2.43.3