[PATCH 1/5] dmr/i915: Displayport - Add a function to set the training pattern

[Todd Previte <tprevite@gmail.com>]

Adds a function to set the training pattern for Displayport. This is
functionality required to establish more fine-grained control over
the Displayport interface, both for operational reliability and
compliance testing.

Signed-off-by: Todd Previte <tprevite@gmail.com>
---
 drivers/gpu/drm/i915/i915_reg.h |  2 ++
 drivers/gpu/drm/i915/intel_dp.c | 70 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index adcb9c7..0f0d549 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5303,6 +5303,8 @@ enum punit_power_well {
 #define  DP_TP_CTL_LINK_TRAIN_NORMAL		(3<<8)
 #define  DP_TP_CTL_SCRAMBLE_DISABLE		(1<<7)
 
+#define DP_TRAINING_PATTERN_MASK_1P2	0x7
+
 /* DisplayPort Transport Status */
 #define DP_TP_STATUS_A			0x64044
 #define DP_TP_STATUS_B			0x64144
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 6f767e5..64c9803 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2356,6 +2356,76 @@ intel_dp_set_signal_levels(struct intel_dp *intel_dp, uint32_t *DP)
 	*DP = (*DP & ~mask) | signal_levels;
 }
 
+uint32_t 
+intel_dp_set_training_pattern(uint8_t training_pattern, 
+							  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;
+	uint8_t buf[sizeof(intel_dp->train_set) + 1];
+	int ret, len;
+
+	uint32_t reg_value, ctrl_reg, tp_select = 0;
+	uint32_t tp_mask = DP_TRAINING_PATTERN_MASK;
+
+	if (HAS_DDI(dev))
+		ctrl_reg = DP_TP_CTL(port);
+	else
+		ctrl_reg = intel_dp->output_reg;
+
+	reg_value = I915_READ(ctrl_reg);
+
+	// Check DPCD revision to enable TP3
+	if (intel_dp->dpcd[0] >= 12)
+		tp_mask = DP_TRAINING_PATTERN_MASK_1P2;
+
+	// Mask selection above ensures TP3 does not get enabled for < DP 1.2
+	switch (training_pattern & tp_mask) {
+		case DP_TRAINING_PATTERN_DISABLE:
+			tp_select = DP_TP_CTL_LINK_TRAIN_NORMAL;
+			break;
+		case DP_TRAINING_PATTERN_1:
+			tp_select = DP_TP_CTL_LINK_TRAIN_PAT1;
+			break;
+		case DP_TRAINING_PATTERN_2:
+			tp_select = DP_TP_CTL_LINK_TRAIN_PAT2;
+			break;
+		case DP_TRAINING_PATTERN_3:
+			tp_select = DP_TP_CTL_LINK_TRAIN_PAT3;
+			break;
+	}
+
+	if (HAS_DDI(dev) || (HAS_PCH_CPT(dev) && (IS_GEN7(dev) || port != PORT_A))) {
+		reg_value &= ~(tp_mask << 8);
+		reg_value |= tp_select;
+	}
+	else {
+		reg_value &= ~(tp_mask << 28);
+		reg_value |= tp_select << 20;
+	}
+
+	I915_WRITE(ctrl_reg, reg_value);
+	POSTING_READ(ctrl_reg);
+
+	buf[0] = training_pattern;
+	if ((training_pattern & tp_mask) ==
+		 DP_TRAINING_PATTERN_DISABLE) {
+		/* don't write DP_TRAINING_LANEx_SET on disable */
+		len = 1;
+	} else {
+		/* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
+		memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
+		len = intel_dp->lane_count + 1;
+	}
+
+	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
+				buf, len);
+
+	return ret == len;
+}
+
 static bool
 intel_dp_set_link_train(struct intel_dp *intel_dp,
 			uint32_t *DP,
-- 
1.8.3.2