[PATCH 020/108] drm/i915/dp_link_training: Add no-fallback link recovery state

[Imre Deak <imre.deak@intel.com>]

Replace the misnamed retrain_disabled flag with a dedicated link
recovery state indicating that no fallback link configurations remain.

This clarifies the meaning of the state: it has always represented the
situation where no further fallback link configurations are available.

While at it, add a TODO comment to the debugfs entry, to expose this
state via a more appropriately named entry.

Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 .../drm/i915/display/intel_dp_link_training.c | 43 +++++++++++++++++--
 1 file changed, 39 insertions(+), 4 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 c44416e0e328f..cbabf01d4b670 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -84,13 +84,21 @@
  *   failures trigger further fallback selections and userspace
  *   notifications.
  *
+ * @INTEL_DP_LINK_RECOVERY_NO_FALLBACK:
+ *   Fallback selection is no longer possible, as no usable fallback link
+ *   configurations remain. Recovery must proceed via userspace modesets
+ *   using the remaining allowed link configuration. Userspace continues
+ *   to be notified of subsequent link training failures.
+ *
  * Describes the link recovery state used by the Intel DP link recovery
  * logic.
  *
  * See also:
  *   - link_recovery_autoretrain_pending()
  *   - link_recovery_autoretrain_allowed()
+ *   - link_recovery_has_no_fallback()
  *   - link_recovery_mark_train_failure()
+ *   - link_recovery_mark_no_fallback()
  *   - link_recovery_reset()
  */
 enum intel_dp_link_recovery_state {
@@ -101,6 +109,7 @@ enum intel_dp_link_recovery_state {
 	INTEL_DP_LINK_RECOVERY_IDLE,
 	INTEL_DP_LINK_RECOVERY_AUTORETRAIN_PENDING,
 	INTEL_DP_LINK_RECOVERY_AUTORETRAIN_DISABLED,
+	INTEL_DP_LINK_RECOVERY_NO_FALLBACK,
 };
 
 struct intel_dp_link_training {
@@ -108,7 +117,6 @@ struct intel_dp_link_training {
 
 	enum intel_dp_link_recovery_state recovery_state;
 
-	bool retrain_disabled;
 	int force_train_failure;
 	bool force_retrain;
 };
@@ -1317,6 +1325,22 @@ link_recovery_autoretrain_allowed(struct intel_dp_link_training *link_training)
 	return link_training->recovery_state < INTEL_DP_LINK_RECOVERY_AUTORETRAIN_DISABLED;
 }
 
+/**
+ * link_recovery_has_no_fallback - check whether fallback is unavailable
+ * @link_training: link training state
+ *
+ * Check whether link fallback configurations are unavailable.
+ *
+ * Return:
+ * - %true  if fallback is unavailable.
+ * - %false otherwise.
+ */
+static bool
+link_recovery_has_no_fallback(struct intel_dp_link_training *link_training)
+{
+	return link_training->recovery_state == INTEL_DP_LINK_RECOVERY_NO_FALLBACK;
+}
+
 /**
  * link_recovery_mark_train_failure - record a link training failure
  * @link_training: link training state
@@ -1344,6 +1368,17 @@ link_recovery_mark_train_failure(struct intel_dp_link_training *link_training)
 	return link_recovery_autoretrain_allowed(link_training);
 }
 
+/**
+ * link_recovery_mark_no_fallback - record that fallback is unavailable
+ * @link_training: link training state
+ *
+ * Record that no more link fallback configuration is available.
+ */
+static void
+link_recovery_mark_no_fallback(struct intel_dp_link_training *link_training)
+{
+	link_training->recovery_state = INTEL_DP_LINK_RECOVERY_NO_FALLBACK;
+}
 
 /**
  * link_recovery_reset - reset the link recovery state
@@ -1950,7 +1985,7 @@ void intel_dp_start_link_train(struct intel_atomic_state *state,
 	if (intel_dp_schedule_fallback_link_training(state, intel_dp, crtc_state))
 		return;
 
-	link_training->retrain_disabled = true;
+	link_recovery_mark_no_fallback(link_training);
 
 	if (!passed)
 		lt_err(intel_dp, DP_PHY_DPRX, "Can't reduce link training parameters after failure\n");
@@ -2550,7 +2585,8 @@ static int i915_dp_link_retrain_disabled_show(struct seq_file *m, void *data)
 
 	intel_dp_flush_connector_commits(connector);
 
-	seq_printf(m, "%s\n", str_yes_no(link_training->retrain_disabled));
+	/* TODO: Expose this via a debugfs entry reflecting what the state represents. */
+	seq_printf(m, "%s\n", str_yes_no(link_recovery_has_no_fallback(link_training)));
 
 	drm_modeset_unlock(&display->drm->mode_config.connection_mutex);
 
@@ -2590,7 +2626,6 @@ void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
 
 void intel_dp_link_training_reset(struct intel_dp_link_training *link_training)
 {
-	link_training->retrain_disabled = false;
 	link_recovery_reset(link_training);
 }
 
-- 
2.49.1