[PATCH 07/47] drm/amd/display: Change dither policy for 10bpc to round

[Rodrigo Siqueira]

From: Krunoslav Kovac <krunoslav.kovac at amd.com>

We use spatial dither by default for all output bpc (6/8/10). While it
makes some sense for FP16, for ARGB2101010 surfaces it makes little
sense as even if we skip color pipeline to preserve bit accuracy,
spatial dither adds random noise so a few percent pixels are 1 bit off.
This commit chages the 10bpc out dither policy to rounding.

Also, in Polaris/Vega times, policy used to be round for 10bpc out; it
looks like it got inadvertently changed for Navi. Difference is only
detectable with capture cards.

Reviewed-by: Aric Cyr <aric.cyr at amd.com>
Reviewed-by: Anthony Koo <anthony.koo at amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira at amd.com>
Signed-off-by: Krunoslav Kovac <krunoslav.kovac at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_resource.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
index f3a9fdd2340d..0a63dcd1cff3 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
@@ -4773,7 +4773,7 @@ void resource_build_bit_depth_reduction_params(struct dc_stream_state *stream,
 			option = DITHER_OPTION_SPATIAL8;
 			break;
 		case COLOR_DEPTH_101010:
-			option = DITHER_OPTION_SPATIAL10;
+			option = DITHER_OPTION_TRUN10;
 			break;
 		default:
 			option = DITHER_OPTION_DISABLE;
@@ -4799,6 +4799,8 @@ void resource_build_bit_depth_reduction_params(struct dc_stream_state *stream,
 			option == DITHER_OPTION_TRUN10_SPATIAL8_FM6) {
 		fmt_bit_depth->flags.TRUNCATE_ENABLED = 1;
 		fmt_bit_depth->flags.TRUNCATE_DEPTH = 2;
+		if (option == DITHER_OPTION_TRUN10)
+			fmt_bit_depth->flags.TRUNCATE_MODE = 1;
 	}
 
 	/* special case - Formatter can only reduce by 4 bits at most.
-- 
2.42.0