[PATCH 20/25] drm/amd/display: add workaround for 4k video underflow

[sunpeng.li at amd.com]

From: Eric Yang <Eric.Yang2 at amd.com>

[Why]
On DCN1, there is an issue where on high BW config on single channel
systems, underflow will be observed if DCC is disabled. This issue
can be observed on several use cases. For this particular case,
it is observed when playing 4k video on 4k desktop with video downscaled
to a certain size.

[How]
Block MPO for this particular case, this will prevent extra BW consumed
from downscaling, working around the underflow.

Signed-off-by: Eric Yang <Eric.Yang2 at amd.com>
Reviewed-by: Yongqiang Sun <yongqiang.sun at amd.com>
Acked-by: Leo Li <sunpeng.li at amd.com>
---
 .../gpu/drm/amd/display/dc/dcn10/dcn10_resource.c  | 51 ++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c
index 3e6a602..ea0628b 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_resource.c
@@ -1131,6 +1131,56 @@ static enum dc_status dcn10_validate_plane(const struct dc_plane_state *plane_st
 	return DC_OK;
 }
 
+static enum dc_status dcn10_validate_global(struct dc *dc, struct dc_state *context)
+{
+	int i, j;
+	bool video_down_scaled = false;
+	bool video_large = false;
+	bool desktop_large = false;
+	bool dcc_disabled = false;
+
+	for (i = 0; i < context->stream_count; i++) {
+		if (context->stream_status[i].plane_count == 0)
+			continue;
+
+		if (context->stream_status[i].plane_count > 2)
+			return false;
+
+		for (j = 0; j < context->stream_status[i].plane_count; j++) {
+			struct dc_plane_state *plane =
+				context->stream_status[i].plane_states[j];
+
+
+			if (plane->format >= SURFACE_PIXEL_FORMAT_VIDEO_BEGIN) {
+
+				if (plane->src_rect.width > plane->dst_rect.width ||
+						plane->src_rect.height > plane->dst_rect.height)
+					video_down_scaled = true;
+
+				if (plane->src_rect.width >= 3840)
+					video_large = true;
+
+			} else {
+				if (plane->src_rect.width >= 3840)
+					desktop_large = true;
+				if (!plane->dcc.enable)
+					dcc_disabled = true;
+			}
+		}
+	}
+
+	/*
+	 * Workaround: On DCN10 there is UMC issue that causes underflow when
+	 * playing 4k video on 4k desktop with video downscaled and single channel
+	 * memory
+	 */
+	if (video_large && desktop_large && video_down_scaled && dcc_disabled &&
+			dc->dcn_soc->number_of_channels == 1)
+		return DC_FAIL_SURFACE_VALIDATE;
+
+	return DC_OK;
+}
+
 static enum dc_status dcn10_get_default_swizzle_mode(struct dc_plane_state *plane_state)
 {
 	enum dc_status result = DC_OK;
@@ -1159,6 +1209,7 @@ static const struct resource_funcs dcn10_res_pool_funcs = {
 	.validate_bandwidth = dcn_validate_bandwidth,
 	.acquire_idle_pipe_for_layer = dcn10_acquire_idle_pipe_for_layer,
 	.validate_plane = dcn10_validate_plane,
+	.validate_global = dcn10_validate_global,
 	.add_stream_to_ctx = dcn10_add_stream_to_ctx,
 	.get_default_swizzle_mode = dcn10_get_default_swizzle_mode
 };
-- 
2.7.4