drm/i915/dp: Add debugfs entry to force link retrain

Add a connector debugfs entry to force retrain an active link. This can
be used to test both custom link parameters (previously forced via the
force_link_rate/lane_count entries) or link train failure scenarios
(previously forced via the force_link_training_failure entry). The entry
will autoreset after the link-retrain is complete.

v2: Add the entry from intel_dp_link_training.c (Jani)
v3: Lock connection_mutex only for the required intel_dp state. (Ville)

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240610164933.2947366-21-imre.deak@intel.com

1 files changed, 45 insertions, 0 deletions

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 a6ea92b54c2f..4da550d6e0ff 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -26,6 +26,7 @@
 #include "intel_dp.h"
 #include "intel_dp_link_training.h"
 #include "intel_encoder.h"
+#include "intel_hotplug.h"
 #include "intel_panel.h"
 
 #define LT_MSG_PREFIX			"[CONNECTOR:%d:%s][ENCODER:%d:%s][%s] "
@@ -1856,6 +1857,47 @@ 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_dp_force_link_retrain_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 = intel_connector_to_intel_dp(connector);
+	int err;
+
+	err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+	if (err)
+		return err;
+
+	*val = intel_dp->link.force_retrain;
+
+	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+	return 0;
+}
+
+static int i915_dp_force_link_retrain_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 = intel_connector_to_intel_dp(connector);
+	int err;
+
+	err = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
+	if (err)
+		return err;
+
+	intel_dp->link.force_retrain = val;
+
+	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
+
+	intel_hpd_trigger_irq(dp_to_dig_port(intel_dp));
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(i915_dp_force_link_retrain_fops,
+			 i915_dp_force_link_retrain_show,
+			 i915_dp_force_link_retrain_write, "%llu\n");
+
 void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
 {
 	struct dentry *root = connector->base.debugfs_entry;
@@ -1878,4 +1920,7 @@ void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
 
 	debugfs_create_file("i915_dp_force_link_training_failure", 0644, root,
 			    connector, &i915_dp_force_link_training_failure_fops);
+
+	debugfs_create_file("i915_dp_force_link_retrain", 0644, root,
+			    connector, &i915_dp_force_link_retrain_fops);
 }