Revert "drm/amd/display: Add writeback enable/disable in dc"

This reverts commit c6d3c7b6.

[WHY & HOW]
The writeback series cause a regression in thunderbolt display.
Signed-off-by: Alex Hung <alex.hung@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -467,25 +467,6 @@ bool dc_stream_add_writeback(struct dc *dc,
 		struct dwbc *dwb = dc->res_pool->dwbc[wb_info->dwb_pipe_inst];
 		dwb->otg_inst = stream_status->primary_otg_inst;
 	}
-
-	if (!dc->hwss.update_bandwidth(dc, dc->current_state)) {
-		dm_error("DC: update_bandwidth failed!\n");
-		return false;
-	}
-
-	/* enable writeback */
-	if (dc->hwss.enable_writeback) {
-		struct dwbc *dwb = dc->res_pool->dwbc[wb_info->dwb_pipe_inst];
-
-		if (dwb->funcs->is_enabled(dwb)) {
-			/* writeback pipe already enabled, only need to update */
-			dc->hwss.update_writeback(dc, wb_info, dc->current_state);
-		} else {
-			/* Enable writeback pipe from scratch*/
-			dc->hwss.enable_writeback(dc, wb_info, dc->current_state);
-		}
-	}
-
 	return true;
 }
 
@@ -530,20 +511,6 @@ bool dc_stream_remove_writeback(struct dc *dc,
 	}
 	stream->num_wb_info = j;
 
-	/* recalculate and apply DML parameters */
-	if (!dc->hwss.update_bandwidth(dc, dc->current_state)) {
-		dm_error("DC: update_bandwidth failed!\n");
-		return false;
-	}
-
-	/* disable writeback */
-	if (dc->hwss.disable_writeback) {
-		struct dwbc *dwb = dc->res_pool->dwbc[dwb_pipe_inst];
-
-		if (dwb->funcs->is_enabled(dwb))
-			dc->hwss.disable_writeback(dc, dwb_pipe_inst);
-	}
-
 	return true;
 }
 

drivers/gpu/drm/amd/display/dc/hwss/dcn30/dcn30_hwseq.c

@@ -367,10 +367,6 @@ void dcn30_enable_writeback(
 	DC_LOG_DWB("%s dwb_pipe_inst = %d, mpcc_inst = %d",\
 		__func__, wb_info->dwb_pipe_inst,\
 		wb_info->mpcc_inst);
-
-	/* Warmup interface */
-	dcn30_mmhubbub_warmup(dc, 1, wb_info);
-
 	/* Update writeback pipe */
 	dcn30_set_writeback(dc, wb_info, context);