drm/amd/display: Implement end of training for hop in DPIA display path

[Why & How]
Clear training pattern sequence for hop in display path once clock
recovery and equalization phases of DP tunnel link training completed.
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Wayne Lin <Wayne.Lin@amd.com>
Acked-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -2389,14 +2389,21 @@ bool perform_link_training_with_retries(
 			dc_link_dp_perform_link_training_skip_aux(link, &current_setting);
 			return true;
 		} else {
-			if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA)
+			/** @todo Consolidate USB4 DP and DPx.x training. */
+			if (link->ep_type == DISPLAY_ENDPOINT_USB4_DPIA) {
 				status = dc_link_dpia_perform_link_training(link,
 									    &current_setting,
 									    skip_video_pattern);
-			else
+
+				/* Transmit idle pattern once training successful. */
+				if (status == LINK_TRAINING_SUCCESS)
+					dp_set_hw_test_pattern(link, DP_TEST_PATTERN_VIDEO_MODE,
+							       NULL, 0);
+			} else {
 				status = dc_link_dp_perform_link_training(link,
 									  &current_setting,
 									  skip_video_pattern);
+			}
 
 			if (status == LINK_TRAINING_SUCCESS)
 				return true;

drivers/gpu/drm/amd/display/dc/core/dc_link_dpia.c

@@ -737,13 +737,84 @@ static enum link_training_result dpia_training_eq_phase(struct dc_link *link,
 }
 
 /* End training of specified hop in display path. */
+static enum dc_status dpcd_clear_lt_pattern(struct dc_link *link, uint32_t hop)
+{
+	union dpcd_training_pattern dpcd_pattern = { {0} };
+	uint32_t dpcd_tps_offset = DP_TRAINING_PATTERN_SET;
+	enum dc_status status;
+
+	if (hop != DPRX)
+		dpcd_tps_offset = DP_TRAINING_PATTERN_SET_PHY_REPEATER1 +
+			((DP_REPEATER_CONFIGURATION_AND_STATUS_SIZE) * (hop - 1));
+
+	status = core_link_write_dpcd(link,
+			DP_TRAINING_PATTERN_SET,
+			&dpcd_pattern.raw,
+			sizeof(dpcd_pattern.raw));
+
+	return status;
+}
+
+/* End training of specified hop in display path.
+ *
+ * In transparent LTTPR mode:
+ * - driver clears training pattern for the specified hop in DPCD.
+ * In non-transparent LTTPR mode:
+ * - in addition to clearing training pattern, driver issues USB4 tunneling
+ * (SET_CONFIG) messages to notify DPOA when training is done for first hop
+ * (DPTX-to-DPIA) and last hop (DPRX).
+ *
+ * @param link DPIA link being trained.
+ * @param hop The Hop in display path. DPRX = 0.
+ */
 static enum link_training_result dpia_training_end(struct dc_link *link,
 		uint32_t hop)
 {
-	enum link_training_result result;
+	enum link_training_result result = LINK_TRAINING_SUCCESS;
+	uint8_t repeater_cnt = 0; /* Number of hops/repeaters in display path. */
+	enum dc_status status;
+
+	if (link->lttpr_mode == LTTPR_MODE_NON_TRANSPARENT) {
+		repeater_cnt = dp_convert_to_count(link->dpcd_caps.lttpr_caps.phy_repeater_cnt);
 
-	/** @todo Fail until implemented. */
-	result = LINK_TRAINING_ABORT;
+		if (hop == repeater_cnt) { /* DPTX-to-DPIA */
+			/* Send SET_CONFIG(SET_TRAINING:0xff) to notify DPOA that
+			 * DPTX-to-DPIA hop trained. No DPCD write needed for first hop.
+			 */
+			status = core_link_send_set_config(link,
+					DPIA_SET_CFG_SET_TRAINING,
+					DPIA_TS_UFP_DONE);
+			if (status != DC_OK)
+				result = LINK_TRAINING_ABORT;
+		} else { /* DPOA-to-x */
+			/* Write 0x0 to TRAINING_PATTERN_SET */
+			status = dpcd_clear_lt_pattern(link, hop);
+			if (status != DC_OK)
+				result = LINK_TRAINING_ABORT;
+		}
+
+		/* Notify DPOA that non-transparent link training of DPRX done. */
+		if (hop == DPRX && result != LINK_TRAINING_ABORT) {
+			status = core_link_send_set_config(link,
+					DPIA_SET_CFG_SET_TRAINING,
+					DPIA_TS_DPRX_DONE);
+			if (status != DC_OK)
+				result = LINK_TRAINING_ABORT;
+		}
+
+	} else { /* non-LTTPR or transparent LTTPR. */
+		/* Write 0x0 to TRAINING_PATTERN_SET */
+		status = dpcd_clear_lt_pattern(link, hop);
+		if (status != DC_OK)
+			result = LINK_TRAINING_ABORT;
+	}
+
+	DC_LOG_HW_LINK_TRAINING("%s\n DPIA(%d) end\n - hop(%d)\n - result(%d)\n - LTTPR mode(%d)\n",
+				__func__,
+				link->link_id.enum_id - ENUM_ID_1,
+				hop,
+				result,
+				link->lttpr_mode);
 
 	return result;
 }