drm/amd/display: support proper mst payload removal when link is not in mst mode in dc

[why]
When user unplugs mst hubs, the current code will forcefully zero
entire mst payload allocation table structure stored in link before we
deallocate actual payload when disabling stream.

During the first disable stream sequence, we will use current mst
payload allocation table to determine if link should be turned off.
Because we zero out it before we are disabling stream, the payload
allocation table stored in link doesn't represent the actual allocation status,
so we turn off link at the first disable stream without waiting until all
streams' payloads have been deallocated. This avoilates the designed
deallocation sequence and caused system hang in DP2 scenario.

[how]
Remove payload during deallocation and never zero payload allocation structure
without actually deallocating payload.
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -848,20 +848,13 @@ static bool discover_dp_mst_topology(struct dc_link *link, enum dc_detect_reason
 
 bool reset_cur_dp_mst_topology(struct dc_link *link)
 {
-	bool result = false;
 	DC_LOGGER_INIT(link->ctx->logger);
 
 	LINK_INFO("link=%d, mst branch is now Disconnected\n",
 		  link->link_index);
 
 	revert_dpia_mst_dsc_always_on_wa(link);
-	result = dm_helpers_dp_mst_stop_top_mgr(link->ctx, link);
-
-	link->mst_stream_alloc_table.stream_count = 0;
-	memset(link->mst_stream_alloc_table.stream_allocations,
-			0,
-			sizeof(link->mst_stream_alloc_table.stream_allocations));
-	return result;
+	return dm_helpers_dp_mst_stop_top_mgr(link->ctx, link);
 }
 
 static bool should_prepare_phy_clocks_for_link_verification(const struct dc *dc,
@@ -3570,6 +3563,35 @@ static void update_mst_stream_alloc_table(
 				work_table[i];
 }
 
+static void remove_stream_from_alloc_table(
+		struct dc_link *link,
+		struct stream_encoder *dio_stream_enc,
+		struct hpo_dp_stream_encoder *hpo_dp_stream_enc)
+{
+	int i = 0;
+	struct link_mst_stream_allocation_table *table =
+			&link->mst_stream_alloc_table;
+
+	if (hpo_dp_stream_enc) {
+		for (; i < table->stream_count; i++)
+			if (hpo_dp_stream_enc == table->stream_allocations[i].hpo_dp_stream_enc)
+				break;
+	} else {
+		for (; i < table->stream_count; i++)
+			if (dio_stream_enc == table->stream_allocations[i].stream_enc)
+				break;
+	}
+
+	if (i < table->stream_count) {
+		i++;
+		for (; i < table->stream_count; i++)
+			table->stream_allocations[i-1] = table->stream_allocations[i];
+		memset(&table->stream_allocations[table->stream_count-1], 0,
+				sizeof(struct link_mst_stream_allocation));
+		table->stream_count--;
+	}
+}
+
 static void dc_log_vcp_x_y(const struct dc_link *link, struct fixed31_32 avg_time_slots_per_mtp)
 {
 	const uint32_t VCP_Y_PRECISION = 1000;
@@ -3987,26 +4009,32 @@ static enum dc_status deallocate_mst_payload(struct pipe_ctx *pipe_ctx)
 				&empty_link_settings,
 				avg_time_slots_per_mtp);
 
-	/* TODO: which component is responsible for remove payload table? */
 	if (mst_mode) {
+		/* when link is in mst mode, reply on mst manager to remove
+		 * payload
+		 */
 		if (dm_helpers_dp_mst_write_payload_allocation_table(
 				stream->ctx,
 				stream,
 				&proposed_table,
-				false)) {
+				false))
 
 			update_mst_stream_alloc_table(
 					link,
 					pipe_ctx->stream_res.stream_enc,
 					pipe_ctx->stream_res.hpo_dp_stream_enc,
 					&proposed_table);
-		}
-		else {
+		else
 			DC_LOG_WARNING("Failed to update"
 					"MST allocation table for"
 					"pipe idx:%d\n",
 					pipe_ctx->pipe_idx);
-		}
+	} else {
+		/* when link is no longer in mst mode (mst hub unplugged),
+		 * remove payload with default dc logic
+		 */
+		remove_stream_from_alloc_table(link, pipe_ctx->stream_res.stream_enc,
+				pipe_ctx->stream_res.hpo_dp_stream_enc);
 	}
 
 	DC_LOG_MST("%s"