drm/i915/dp: Add debugfs entry to force link training failure

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.

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/20240610164933.2947366-20-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 8e9245161e4d8124dd12b1eea54eeda5a8814edd..9ae22e8dd2e273246efd3c5b708b09511f8486f9 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1776,6 +1776,7 @@ struct intel_dp {
                bool retrain_disabled;
                /* Sequential link training failures after a passing LT */
                int seq_train_failures;
+               int force_train_failure;
        } link;
        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 184206067fa6105fcdeac8d0a6cb52b8cc43bf73..a6ea92b54c2f4ef34e4bd0c9d9fe2d85fc31c3a1 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -1504,7 +1504,10 @@ void intel_dp_start_link_train(struct intel_atomic_state *state,
        else
                passed = intel_dp_link_train_all_phys(intel_dp, crtc_state, lttpr_count);
 
-       if (passed) {
+       if (intel_dp->link.force_train_failure) {
+               intel_dp->link.force_train_failure--;
+               lt_dbg(intel_dp, DP_PHY_DPRX, "Forcing link training failure\n");
+       } else if (passed) {
                intel_dp->link.seq_train_failures = 0;
                intel_encoder_link_check_queue_work(encoder, 2000);
                return;
@@ -1539,7 +1542,10 @@ void intel_dp_start_link_train(struct intel_atomic_state *state,
 
        intel_dp->link.retrain_disabled = true;
 
-       lt_err(intel_dp, DP_PHY_DPRX, "Can't reduce link training parameters after failure\n");
+       if (!passed)
+               lt_err(intel_dp, DP_PHY_DPRX, "Can't reduce link training parameters after failure\n");
+       else
+               lt_dbg(intel_dp, DP_PHY_DPRX, "Can't reduce link training parameters after forced failure\n");
 }
 
 void intel_dp_128b132b_sdp_crc16(struct intel_dp *intel_dp,
@@ -1808,6 +1814,48 @@ static int i915_dp_max_lane_count_show(void *data, u64 *val)
 }
 DEFINE_DEBUGFS_ATTRIBUTE(i915_dp_max_lane_count_fops, i915_dp_max_lane_count_show, NULL, "%llu\n");
 
+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 = 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_train_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 = intel_connector_to_intel_dp(connector);
+       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->link.force_train_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");
+
 void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
 {
        struct dentry *root = connector->base.debugfs_entry;
@@ -1827,4 +1875,7 @@ void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
 
        debugfs_create_file("i915_dp_max_lane_count", 0444, root,
                            connector, &i915_dp_max_lane_count_fops);
+
+       debugfs_create_file("i915_dp_force_link_training_failure", 0644, root,
+                           connector, &i915_dp_force_link_training_failure_fops);
 }