[PATCH] drm/i915: hsw: fix link training for DP/eDP on port-A

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

According to BSpec the link training sequence on HSW port-A should be as
follows:

1. link training: clock recovery
2. link training: equalization
3. display pipe enable
4. link training: disable (set normal mode)

Contrary to this at the moment we do step 4. already after step 2. Fix
this by adding a new intel_dp_stop_link_training function, so that we'll
end up with the following functions corresponding to the above steps:

intel_dp_start_link_train    -> step 1.
intel_dp_complete_link_train -> step 2.
intel_dp_stop_link_train     -> step 4.

For port-A we'll call intel_dp_stop_link_train only after enabling the
pipe for everything else we'll call it right after
intel_dp_complete_link_train to preserve the current behavior.

Tested on HSW/HSW-ULT.

Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/intel_ddi.c |    5 ++++
 drivers/gpu/drm/i915/intel_dp.c  |   49 ++++++++++++++++++++++++++------------
 drivers/gpu/drm/i915/intel_drv.h |    1 +
 3 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index eef450b..d7da1ca 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1265,6 +1265,8 @@ static void intel_ddi_pre_enable(struct intel_encoder *intel_encoder)
 		intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
 		intel_dp_start_link_train(intel_dp);
 		intel_dp_complete_link_train(intel_dp);
+		if (port != PORT_A)
+			intel_dp_stop_link_train(intel_dp);
 	}
 }
 
@@ -1326,6 +1328,9 @@ static void intel_enable_ddi(struct intel_encoder *intel_encoder)
 	} else if (type == INTEL_OUTPUT_EDP) {
 		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 
+		if (port == PORT_A)
+			intel_dp_stop_link_train(intel_dp);
+
 		ironlake_edp_backlight_on(intel_dp);
 	}
 
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index dd4100f..57f4585 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1389,6 +1389,7 @@ static void intel_enable_dp(struct intel_encoder *encoder)
 	ironlake_edp_panel_on(intel_dp);
 	ironlake_edp_panel_vdd_off(intel_dp, true);
 	intel_dp_complete_link_train(intel_dp);
+	intel_dp_stop_link_train(intel_dp);
 	ironlake_edp_backlight_on(intel_dp);
 
 	if (IS_VALLEYVIEW(dev)) {
@@ -1887,10 +1888,9 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	enum port port = intel_dig_port->port;
 	int ret;
-	uint32_t temp;
 
 	if (HAS_DDI(dev)) {
-		temp = I915_READ(DP_TP_CTL(port));
+		uint32_t temp = I915_READ(DP_TP_CTL(port));
 
 		if (dp_train_pat & DP_LINK_SCRAMBLING_DISABLE)
 			temp |= DP_TP_CTL_SCRAMBLE_DISABLE;
@@ -1900,18 +1900,6 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
 		temp &= ~DP_TP_CTL_LINK_TRAIN_MASK;
 		switch (dp_train_pat & DP_TRAINING_PATTERN_MASK) {
 		case DP_TRAINING_PATTERN_DISABLE:
-
-			if (port != PORT_A) {
-				temp |= DP_TP_CTL_LINK_TRAIN_IDLE;
-				I915_WRITE(DP_TP_CTL(port), temp);
-
-				if (wait_for((I915_READ(DP_TP_STATUS(port)) &
-					      DP_TP_STATUS_IDLE_DONE), 1))
-					DRM_ERROR("Timed out waiting for DP idle patterns\n");
-
-				temp &= ~DP_TP_CTL_LINK_TRAIN_MASK;
-			}
-
 			temp |= DP_TP_CTL_LINK_TRAIN_NORMAL;
 
 			break;
@@ -1987,6 +1975,27 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
 	return true;
 }
 
+static void intel_dp_idle_link_train(struct intel_dp *intel_dp)
+{
+	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
+	struct drm_device *dev = intel_dig_port->base.base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	enum port port = intel_dig_port->port;
+	uint32_t l;
+
+	if (!HAS_DDI(dev) || port == PORT_A)
+		return;
+
+	l = I915_READ(DP_TP_CTL(port));
+	l &= ~DP_TP_CTL_LINK_TRAIN_MASK;
+	l |= DP_TP_CTL_LINK_TRAIN_IDLE;
+	I915_WRITE(DP_TP_CTL(port), l);
+
+	if (wait_for((I915_READ(DP_TP_STATUS(port)) & DP_TP_STATUS_IDLE_DONE),
+		     1))
+		DRM_ERROR("Timed out waiting for DP idle patterns\n");
+}
+
 /* Enable corresponding port and start training pattern 1 */
 void
 intel_dp_start_link_train(struct intel_dp *intel_dp)
@@ -2129,10 +2138,19 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
 		++tries;
 	}
 
+	intel_dp_idle_link_train(intel_dp);
+
+	intel_dp->DP = DP;
+
 	if (channel_eq)
 		DRM_DEBUG_KMS("Channel EQ done. DP Training successfull\n");
 
-	intel_dp_set_link_train(intel_dp, DP, DP_TRAINING_PATTERN_DISABLE);
+}
+
+void intel_dp_stop_link_train(struct intel_dp *intel_dp)
+{
+	intel_dp_set_link_train(intel_dp, intel_dp->DP,
+				DP_TRAINING_PATTERN_DISABLE);
 }
 
 static void
@@ -2340,6 +2358,7 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 			      drm_get_encoder_name(&intel_encoder->base));
 		intel_dp_start_link_train(intel_dp);
 		intel_dp_complete_link_train(intel_dp);
+		intel_dp_stop_link_train(intel_dp);
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 66922f8..684a90e 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -525,6 +525,7 @@ extern void intel_dp_init_connector(struct intel_digital_port *intel_dig_port,
 extern void intel_dp_init_link_config(struct intel_dp *intel_dp);
 extern void intel_dp_start_link_train(struct intel_dp *intel_dp);
 extern void intel_dp_complete_link_train(struct intel_dp *intel_dp);
+extern void intel_dp_stop_link_train(struct intel_dp *intel_dp);
 extern void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);
 extern void intel_dp_encoder_destroy(struct drm_encoder *encoder);
 extern void intel_dp_check_link_status(struct intel_dp *intel_dp);
-- 
1.7.10.4