[5/9] drm/i915/dp: Implement the POST_LT_ADJ_REQ sequence

Commit Message

Ville Syrjala Feb. 24, 2025, 5:26 p.m. UTC

From: Ville Syrjälä <[e-mail]>

Implement the POST_LT_ADJ_REQ sequence, which should be used
to further fine tune the link if TPS4 is not supported.
The POST_LT_ADJ_REQ sequence will be performed after
the normal link training has succeeded.

Only the final hop between the last LTTPR and DPRX will
perform the POST_LT_ADJ_REQ adjustment. The earlier hops
will use TPS4 instead since it's mandatory for LTTPRs.

start The sequence will terminate when the sink clears the
"in progress" flag, the vswing/pre-emphasis values have
changed six times, or the vswing/pre-emphasis values have
remained unchanged for 200 ms.

Signed-off-by: Ville Syrjälä <[e-mail]>
---
 .../drm/i915/display/intel_dp_link_training.c | 128 +++++++++++++++++-
 .../drm/i915/display/intel_dp_link_training.h |   2 +-
 drivers/gpu/drm/i915/display/intel_dp_mst.c   |   2 +-
 3 files changed, 128 insertions(+), 4 deletions(-)

Patch

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 2506996bf16d..8863fc2c44ff 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -738,11 +738,14 @@  static void intel_dp_update_downspread_ctrl(struct intel_dp *intel_dp,
 
 void intel_dp_link_training_set_bw(struct intel_dp *intel_dp,
 				   int link_bw, int rate_select, int lane_count,
-				   bool enhanced_framing)
+				   bool enhanced_framing, bool post_lt_adj_req)
 {
 	if (enhanced_framing)
 		lane_count |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
 
+	if (post_lt_adj_req)
+		lane_count |= DP_POST_LT_ADJ_REQ_GRANTED;
+
 	if (link_bw) {
 		/* DP and eDP v1.3 and earlier link bw set method. */
 		u8 link_config[] = { link_bw, lane_count };
@@ -764,12 +767,25 @@  void intel_dp_link_training_set_bw(struct intel_dp *intel_dp,
 	}
 }
 
+static u32 intel_dp_training_pattern(struct intel_dp *intel_dp,
+				     const struct intel_crtc_state *crtc_state,
+				     enum drm_dp_phy dp_phy);
+
+static bool intel_dp_use_post_lt_adj_req(struct intel_dp *intel_dp,
+					 const struct intel_crtc_state *crtc_state)
+{
+	return intel_dp->set_idle_link_train &&
+		drm_dp_post_lt_adj_req_supported(intel_dp->dpcd) &&
+		intel_dp_training_pattern(intel_dp, crtc_state, DP_PHY_DPRX) != DP_TRAINING_PATTERN_4;
+}
+
 static void intel_dp_update_link_bw_set(struct intel_dp *intel_dp,
 					const struct intel_crtc_state *crtc_state,
 					u8 link_bw, u8 rate_select)
 {
 	intel_dp_link_training_set_bw(intel_dp, link_bw, rate_select, crtc_state->lane_count,
-				      crtc_state->enhanced_framing);
+				      crtc_state->enhanced_framing,
+				      intel_dp_use_post_lt_adj_req(intel_dp, crtc_state));
 }
 
 /*
@@ -1087,6 +1103,109 @@  intel_dp_link_training_channel_equalization(struct intel_dp *intel_dp,
 	return channel_eq;
 }
 
+static bool
+intel_dp_post_lt_adj_req(struct intel_dp *intel_dp,
+			 const struct intel_crtc_state *crtc_state)
+{
+	u8 link_status[DP_LINK_STATUS_SIZE];
+	unsigned long deadline;
+	bool timeout = false;
+	bool success = false;
+	int changes = 0;
+
+	if (!intel_dp_use_post_lt_adj_req(intel_dp, crtc_state))
+		return true;
+
+	if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
+					     link_status) < 0) {
+		lt_err(intel_dp, DP_PHY_DPRX, "Failed to get link status\n");
+		return false;
+	}
+
+	deadline = jiffies + msecs_to_jiffies_timeout(200);
+
+	for (;;) {
+		/* Make sure clock is still ok */
+		if (!drm_dp_clock_recovery_ok(link_status,
+					      crtc_state->lane_count)) {
+			intel_dp_dump_link_status(intel_dp, DP_PHY_DPRX, link_status);
+			lt_dbg(intel_dp, DP_PHY_DPRX,
+			       "Clock recovery check failed, cannot continue POST_LT_ADJ_REQ\n");
+			break;
+		}
+
+		if (!drm_dp_channel_eq_ok(link_status,
+					  crtc_state->lane_count)) {
+			intel_dp_dump_link_status(intel_dp, DP_PHY_DPRX, link_status);
+			lt_dbg(intel_dp, DP_PHY_DPRX, "Channel EQ check failed. cannot continue POST_LT_ADJ_REQ\n");
+			break;
+		}
+
+		if (!drm_dp_post_lt_adj_req_in_progress(link_status)) {
+			success = true;
+			intel_dp_dump_link_status(intel_dp, DP_PHY_DPRX, link_status);
+			lt_dbg(intel_dp, DP_PHY_DPRX,
+			       "POST_LT_ADJ_REQ done (%d changes). DP Training successful\n", changes);
+			break;
+		}
+
+		if (changes == 6) {
+			success = true;
+			intel_dp_dump_link_status(intel_dp, DP_PHY_DPRX, link_status);
+			lt_dbg(intel_dp, DP_PHY_DPRX,
+			       "POST_LT_ADJ_REQ limit reached (%d changes). DP Training successful\n", changes);
+			break;
+		}
+
+		if (timeout) {
+			success = true;
+			intel_dp_dump_link_status(intel_dp, DP_PHY_DPRX, link_status);
+			lt_dbg(intel_dp, DP_PHY_DPRX,
+			       "POST_LT_ADJ_REQ timeout reached (%d changes). DP Training successful\n", changes);
+			break;
+		}
+
+		fsleep(5000);
+
+		if (drm_dp_dpcd_read_phy_link_status(&intel_dp->aux, DP_PHY_DPRX,
+						     link_status) < 0) {
+			lt_err(intel_dp, DP_PHY_DPRX, "Failed to get link status\n");
+			break;
+		}
+
+		/* Update training set as requested by target */
+		if (intel_dp_get_adjust_train(intel_dp, crtc_state, DP_PHY_DPRX, link_status)) {
+			deadline = jiffies + msecs_to_jiffies_timeout(200);
+			changes++;
+
+			if (!intel_dp_update_link_train(intel_dp, crtc_state, DP_PHY_DPRX)) {
+				lt_err(intel_dp, DP_PHY_DPRX, "Failed to update link training\n");
+				break;
+			}
+		} else if (time_after(jiffies, deadline)) {
+			timeout = true;
+		}
+	}
+
+	return success;
+}
+
+static void intel_dp_stop_post_lt_adj_req(struct intel_dp *intel_dp,
+					  const struct intel_crtc_state *crtc_state)
+{
+	u8 lane_count;
+
+	if (!intel_dp_use_post_lt_adj_req(intel_dp, crtc_state))
+		return;
+
+	/* clear DP_POST_LT_ADJ_REQ_GRANTED */
+	lane_count = crtc_state->lane_count;
+	if (crtc_state->enhanced_framing)
+		lane_count |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
+
+	drm_dp_dpcd_writeb(&intel_dp->aux, DP_LANE_COUNT_SET, lane_count);
+}
+
 static bool intel_dp_disable_dpcd_training_pattern(struct intel_dp *intel_dp,
 						   enum drm_dp_phy dp_phy)
 {
@@ -1372,6 +1491,11 @@  intel_dp_link_train_all_phys(struct intel_dp *intel_dp,
 		intel_dp->set_idle_link_train(intel_dp, crtc_state);
 	}
 
+	if (ret)
+		ret = intel_dp_post_lt_adj_req(intel_dp, crtc_state);
+
+	intel_dp_stop_post_lt_adj_req(intel_dp, crtc_state);
+
 	return ret;
 }
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.h b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
index 1ba22ed6db08..33dcbde6a408 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.h
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
@@ -21,7 +21,7 @@  void intel_dp_link_training_set_mode(struct intel_dp *intel_dp,
 				     int link_rate, bool is_vrr);
 void intel_dp_link_training_set_bw(struct intel_dp *intel_dp,
 				   int link_bw, int rate_select, int lane_count,
-				   bool enhanced_framing);
+				   bool enhanced_framing, bool post_lt_adj_req);
 
 bool intel_dp_get_adjust_train(struct intel_dp *intel_dp,
 			       const struct intel_crtc_state *crtc_state,
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 167e4a70ab12..d937143ed10f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -2109,7 +2109,7 @@  void intel_dp_mst_prepare_probe(struct intel_dp *intel_dp)
 
 	intel_dp_link_training_set_mode(intel_dp, link_rate, false);
 	intel_dp_link_training_set_bw(intel_dp, link_bw, rate_select, lane_count,
-				      drm_dp_enhanced_frame_cap(intel_dp->dpcd));
+				      drm_dp_enhanced_frame_cap(intel_dp->dpcd), false);
 
 	intel_mst_set_probed_link_params(intel_dp, link_rate, lane_count);
 }