[Intel-gfx] [PATCH] drm/i915: Enable 5.4Ghz (HBR2) link rate for Displayport 1.2-capable devices

[Todd Previte]

For HSW+ platforms, enable the 5.4Ghz (HBR2) link rate for devices that support it. The
sink device must report that is supports Displayport 1.2 and the HBR2 bit rate in the
DPCD in order to use HBR2.
---
 drivers/gpu/drm/i915/intel_dp.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 7df5085..f92d1c0 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -102,7 +102,10 @@ intel_dp_max_link_bw(struct intel_dp *intel_dp)
 	case DP_LINK_BW_2_7:
 		break;
 	case DP_LINK_BW_5_4: /* 1.2 capable displays may advertise higher bw */
-		max_link_bw = DP_LINK_BW_2_7;
+        if (intel_dp->dpcd[DP_DPCD_REV] == 0x12)
+            max_link_bw = DP_LINK_BW_5_4;
+        else
+            max_link_bw = DP_LINK_BW_2_7;
 		break;
 	default:
 		WARN(1, "invalid max DP link bw val %x, using 1.62Gbps\n",
@@ -805,9 +808,10 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	struct intel_connector *intel_connector = intel_dp->attached_connector;
 	int lane_count, clock;
 	int max_lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
-	int max_clock = intel_dp_max_link_bw(intel_dp) == DP_LINK_BW_2_7 ? 1 : 0;
+    /* Conveniently, the link BW constants become indices with a shift...*/
+    int max_clock = intel_dp_max_link_bw(intel_dp) >> 3;
 	int bpp, mode_rate;
-	static int bws[2] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7 };
+	static int bws[] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 };
 	int link_avail, link_clock;
 
 	if (HAS_PCH_SPLIT(dev) && !HAS_DDI(dev) && port != PORT_A)
@@ -2621,10 +2625,15 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
 	bool channel_eq = false;
 	int tries, cr_tries;
 	uint32_t DP = intel_dp->DP;
+    uint32_t training_pattern = DP_TRAINING_PATTERN_2;
+
+    /* Training Pattern 3 for HBR2 */
+    if (intel_dp->link_bw == DP_LINK_BW_5_4)
+        training_pattern = DP_TRAINING_PATTERN_3;
 
 	/* channel equalization */
 	if (!intel_dp_set_link_train(intel_dp, &DP,
-				     DP_TRAINING_PATTERN_2 |
+				     training_pattern |
 				     DP_LINK_SCRAMBLING_DISABLE)) {
 		DRM_ERROR("failed to start channel equalization\n");
 		return;
@@ -2652,7 +2661,7 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
 		if (!drm_dp_clock_recovery_ok(link_status, intel_dp->lane_count)) {
 			intel_dp_start_link_train(intel_dp);
 			intel_dp_set_link_train(intel_dp, &DP,
-						DP_TRAINING_PATTERN_2 |
+						training_pattern |
 						DP_LINK_SCRAMBLING_DISABLE);
 			cr_tries++;
 			continue;
@@ -2668,7 +2677,7 @@ intel_dp_complete_link_train(struct intel_dp *intel_dp)
 			intel_dp_link_down(intel_dp);
 			intel_dp_start_link_train(intel_dp);
 			intel_dp_set_link_train(intel_dp, &DP,
-						DP_TRAINING_PATTERN_2 |
+						training_pattern |
 						DP_LINK_SCRAMBLING_DISABLE);
 			tries = 0;
 			cr_tries++;
-- 
1.8.1.2