[PATCH AUTOSEL 4.20 221/304] drm/amd/display: fix YCbCr420 blank color

[Sasha Levin <sashal@kernel.org>]

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

[ Upstream commit 12750d1647f118496f1da727146f255f5e44d500 ]

[Why]
YCbCr420 packing format uses two chanels for luma, and 1
channel for both chroma component. Our previous implementation
did not account for this and results in every other pixel having
very high luma value, showing greyish color instead of black.

YCbCr444 = <Y1, Cb1, Cr1>; <Y2, Cb2, Cr2> .....
YCbCr420 = <Y1, Y2,  Cb1>; <Y3, Y4,  Cr1> .....

[How]
Program the second channel with the black color value for luma
as well.

Signed-off-by: Eric Yang <Eric.Yang2@amd.com>
Reviewed-by: Hugo Hu <Hugo.Hu@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .../drm/amd/display/dc/dce110/dce110_hw_sequencer.c   | 11 ++++++++++-
 .../gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c |  9 +++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
index a6bcb90e8419..4443a916a0fb 100644
--- a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
@@ -1268,10 +1268,19 @@ static void program_scaler(const struct dc *dc,
 		pipe_ctx->plane_res.scl_data.lb_params.depth,
 		&pipe_ctx->stream->bit_depth_params);
 
-	if (pipe_ctx->stream_res.tg->funcs->set_overscan_blank_color)
+	if (pipe_ctx->stream_res.tg->funcs->set_overscan_blank_color) {
+		/*
+		 * The way 420 is packed, 2 channels carry Y component, 1 channel
+		 * alternate between Cb and Cr, so both channels need the pixel
+		 * value for Y
+		 */
+		if (pipe_ctx->stream->timing.pixel_encoding == PIXEL_ENCODING_YCBCR420)
+			color.color_r_cr = color.color_g_y;
+
 		pipe_ctx->stream_res.tg->funcs->set_overscan_blank_color(
 				pipe_ctx->stream_res.tg,
 				&color);
+	}
 
 	pipe_ctx->plane_res.xfm->funcs->transform_set_scaler(pipe_ctx->plane_res.xfm,
 		&pipe_ctx->plane_res.scl_data);
diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
index 32e4c653b1b4..220ba828748d 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
@@ -2165,6 +2165,15 @@ static void dcn10_blank_pixel_data(
 	color_space = stream->output_color_space;
 	color_space_to_black_color(dc, color_space, &black_color);
 
+	/*
+	 * The way 420 is packed, 2 channels carry Y component, 1 channel
+	 * alternate between Cb and Cr, so both channels need the pixel
+	 * value for Y
+	 */
+	if (stream->timing.pixel_encoding == PIXEL_ENCODING_YCBCR420)
+		black_color.color_r_cr = black_color.color_g_y;
+
+
 	if (stream_res->tg->funcs->set_blank_color)
 		stream_res->tg->funcs->set_blank_color(
 				stream_res->tg,
-- 
2.19.1