diff mbox series

[v2,2/6] drm/i915: Simplify the link training functions

Message ID 20200924184805.294493-3-imre.deak@intel.com
State New, archived
Headers show
Series drm/i915: Add support for LTTPR non-transparent link training mode | expand

Commit Message

Imre Deak Sept. 24, 2020, 6:48 p.m. UTC
Split the prepare, link training, fallback-handling steps into their own
functions for clarity and as a preparation for the upcoming LTTPR
changes.

While at it also:
- Unexport and inline intel_dp_set_idle_link_train(), which is used at a
  single place.
- Add some documentation to functions that are exported or that can use
  a better description about which part of the LT sequence they
  implement.

v2: (Ville)
- Unexport/inline intel_dp_set_idle_link_train()
- Make the documentation of
  intel_dp_prepare_link_train()/intel_dp_stop_link_train() more accurate
  wrt. HW specific details.

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>
---
 drivers/gpu/drm/i915/display/intel_dp.c       |  6 --
 drivers/gpu/drm/i915/display/intel_dp.h       |  1 -
 .../drm/i915/display/intel_dp_link_training.c | 90 ++++++++++++++-----
 3 files changed, 70 insertions(+), 27 deletions(-)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index bba9669e0e57..b21f42193a11 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4508,12 +4508,6 @@  intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
 	intel_dp->set_link_train(intel_dp, dp_train_pat);
 }
 
-void intel_dp_set_idle_link_train(struct intel_dp *intel_dp)
-{
-	if (intel_dp->set_idle_link_train)
-		intel_dp->set_idle_link_train(intel_dp);
-}
-
 static void
 intel_dp_link_down(struct intel_encoder *encoder,
 		   const struct intel_crtc_state *old_crtc_state)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index 08a1c0aa8b94..ca8319d6c63c 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -95,7 +95,6 @@  intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
 				       u8 dp_train_pat);
 void
 intel_dp_set_signal_levels(struct intel_dp *intel_dp);
-void intel_dp_set_idle_link_train(struct intel_dp *intel_dp);
 void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
 			   u8 *link_bw, u8 *rate_select);
 bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
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 0e1472b1f868..78b0f165fadd 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -146,14 +146,13 @@  static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
 	return true;
 }
 
-/* Enable corresponding port and start training pattern 1 */
-static bool
-intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
+/*
+ * Prepare link training by configuring the link parameters. On DDI platforms
+ * also enable the port here.
+ */
+static void intel_dp_prepare_link_train(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
-	u8 voltage;
-	int voltage_tries, cr_tries, max_cr_tries;
-	bool max_vswing_reached = false;
 	u8 link_config[2];
 	u8 link_bw, rate_select;
 
@@ -187,6 +186,16 @@  intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
 	drm_dp_dpcd_write(&intel_dp->aux, DP_DOWNSPREAD_CTRL, link_config, 2);
 
 	intel_dp->DP |= DP_PORT_EN;
+}
+
+/* Perform the link training clock recovery phase using training pattern 1. */
+static bool
+intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+	u8 voltage;
+	int voltage_tries, cr_tries, max_cr_tries;
+	bool max_vswing_reached = false;
 
 	/* clock recovery */
 	if (!intel_dp_reset_link_train(intel_dp,
@@ -309,6 +318,10 @@  static u32 intel_dp_training_pattern(struct intel_dp *intel_dp)
 	return DP_TRAINING_PATTERN_2;
 }
 
+/*
+ * Perform the link training channel equalization phase using one of training
+ * pattern 2, 3 or 4 depending on the source and sink capabilities.
+ */
 static bool
 intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 {
@@ -373,12 +386,27 @@  intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp)
 			    "Channel equalization failed 5 times\n");
 	}
 
-	intel_dp_set_idle_link_train(intel_dp);
+	if (intel_dp->set_idle_link_train)
+		intel_dp->set_idle_link_train(intel_dp);
 
 	return channel_eq;
-
 }
 
+/**
+ * intel_dp_stop_link_train - stop link training
+ * @intel_dp: DP struct
+ *
+ * Stop the link training of the @intel_dp port, disabling the test pattern
+ * symbol generation on the port and disabling the training pattern in
+ * the sink's DPCD.
+ *
+ * What symbols are output on the port after this point is
+ * platform specific: On DDI/VLV/CHV platforms it will be the idle pattern
+ * with the pipe being disabled, on older platforms it's HW specific if/how an
+ * idle pattern is generated, as the pipe is already enabled here for those.
+ *
+ * This function must be called after intel_dp_start_link_train().
+ */
 void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 {
 	intel_dp->link_trained = true;
@@ -387,30 +415,37 @@  void intel_dp_stop_link_train(struct intel_dp *intel_dp)
 				DP_TRAINING_PATTERN_DISABLE);
 }
 
-void
-intel_dp_start_link_train(struct intel_dp *intel_dp)
+static bool
+intel_dp_link_train(struct intel_dp *intel_dp)
 {
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
+	bool ret = false;
+
+	intel_dp_prepare_link_train(intel_dp);
 
 	if (!intel_dp_link_training_clock_recovery(intel_dp))
-		goto failure_handling;
+		goto out;
+
 	if (!intel_dp_link_training_channel_equalization(intel_dp))
-		goto failure_handling;
+		goto out;
 
-	drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
-		    "[CONNECTOR:%d:%s] Link Training Passed at Link Rate = %d, Lane count = %d",
-		    intel_connector->base.base.id,
-		    intel_connector->base.name,
-		    intel_dp->link_rate, intel_dp->lane_count);
-	return;
+	ret = true;
 
- failure_handling:
+out:
 	drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
-		    "[CONNECTOR:%d:%s] Link Training failed at link rate = %d, lane count = %d",
+		    "[CONNECTOR:%d:%s] Link Training %s at Link Rate = %d, Lane count = %d",
 		    intel_connector->base.base.id,
 		    intel_connector->base.name,
+		    ret ? "passed" : "failed",
 		    intel_dp->link_rate, intel_dp->lane_count);
 
+	return ret;
+}
+
+static void intel_dp_schedule_fallback_link_training(struct intel_dp *intel_dp)
+{
+	struct intel_connector *intel_connector = intel_dp->attached_connector;
+
 	if (intel_dp->hobl_active) {
 		drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
 			    "Link Training failed with HOBL active, not enabling it from now on");
@@ -424,3 +459,18 @@  intel_dp_start_link_train(struct intel_dp *intel_dp)
 	/* Schedule a Hotplug Uevent to userspace to start modeset */
 	schedule_work(&intel_connector->modeset_retry_work);
 }
+
+/**
+ * intel_dp_start_link_train - start link training
+ * @intel_dp: DP struct
+ *
+ * Start the link training of the @intel_dp port, scheduling a fallback
+ * retraining with reduced link rate/lane parameters if the link training
+ * fails.
+ * After calling this function intel_dp_stop_link_train() must be called.
+ */
+void intel_dp_start_link_train(struct intel_dp *intel_dp)
+{
+	if (!intel_dp_link_train(intel_dp))
+		intel_dp_schedule_fallback_link_training(intel_dp);
+}