drm/amd/display: Add dc cap to restrict VSR downscaling src size

- Adds int max_downscale_src_width in dc struct
- Checks and does not support if downscale size is more than 4k (width > 3840)
Signed-off-by: Xingyue Tao <xingyue.tao@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc.h

@@ -203,6 +203,7 @@ struct dc_debug {
 	bool clock_trace;
 	bool validation_trace;
 	bool bandwidth_calcs_trace;
+	int max_downscale_src_width;
 
 	/* stutter efficiency related */
 	bool disable_stutter;

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_dpp.c

@@ -145,12 +145,18 @@ bool dpp_get_optimal_number_of_taps(
 	else
 		pixel_width = scl_data->viewport.width;
 
-	/* Some ASICs does not support  FP16 scaling, so we reject modes require this*/
 	if (scl_data->viewport.width  != scl_data->h_active &&
-		scl_data->viewport.height != scl_data->v_active &&
-		dpp->caps->dscl_data_proc_format == DSCL_DATA_PRCESSING_FIXED_FORMAT &&
-		scl_data->format == PIXEL_FORMAT_FP16)
-		return false;
+		scl_data->viewport.height != scl_data->v_active) {
+
+		/* Some ASICs does not support  FP16 scaling, so we reject modes require this*/
+		if (dpp->caps->dscl_data_proc_format == DSCL_DATA_PRCESSING_FIXED_FORMAT &&
+			scl_data->format == PIXEL_FORMAT_FP16)
+			return false;
+
+		if (dpp->ctx->dc->debug.max_downscale_src_width != 0 &&
+			scl_data->viewport.width > dpp->ctx->dc->debug.max_downscale_src_width)
+			return false;
+	}
 
 	/* TODO: add lb check */
 

drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c

@@ -447,6 +447,7 @@ static const struct dc_debug debug_defaults_drv = {
 		.performance_trace = false,
 		.az_endpoint_mute_only = true,
 		.recovery_enabled = false, /*enable this by default after testing.*/
+		.max_downscale_src_width = 3840,
 };
 
 static const struct dc_debug debug_defaults_diags = {