drm/amd/display: fix link bw calculation for 422 and 420 encoding

Link bw required is reduced when we have chroma subsampling.
Signed-off-by: Eric Yang <Eric.Yang2@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/core/dc_link_dp.c

@@ -1378,6 +1378,11 @@ static uint32_t bandwidth_in_kbps_from_timing(
 {
 	uint32_t bits_per_channel = 0;
 	uint32_t kbps;
+
+	if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR422)
+		bits_per_channel = 12;
+	else{
+
 		switch (timing->display_color_depth) {
 
 		case COLOR_DEPTH_666:
@@ -1401,14 +1406,20 @@ static uint32_t bandwidth_in_kbps_from_timing(
 		default:
 			break;
 		}
+	}
 	ASSERT(bits_per_channel != 0);
 
 	kbps = timing->pix_clk_khz;
 	kbps *= bits_per_channel;
 
-	if (timing->flags.Y_ONLY != 1)
+	if (timing->flags.Y_ONLY != 1) {
 		/*Only YOnly make reduce bandwidth by 1/3 compares to RGB*/
 		kbps *= 3;
+		if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR420)
+			kbps /= 2;
+		else if (timing->pixel_encoding == PIXEL_ENCODING_YCBCR422)
+			kbps = kbps * 2 / 3;
+	}
 
 	return kbps;