[PATCH 03/36] drm/amd/display: Program DSC before enabling link

[Rodrigo Siqueira]

From: Nikola Cornij <nikola.cornij at amd.com>

[why]
Link or DIG BE can't be exposed to a higher stream bandwidth than they
can handle. When DSC is required to fit the stream into the link
bandwidth, DSC has to be programmed before the link is enabled to ensure
this. Without it, intermittent issues such as black screen after S3 or a
hot-plug can be seen with DSC timings like 4k144Hz or 8k60Hz.

[how]
Move DSC programming from before enabling stream to before enabling link

Signed-off-by: Nikola Cornij <nikola.cornij at amd.com>
Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index 67cfff1586e9..ecbf165b5775 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -3040,6 +3040,18 @@ void core_link_enable_stream(
 		if (pipe_ctx->stream->dpms_off)
 			return;
 
+		/* Have to setup DSC before DIG FE and BE are connected (which happens before the
+		 * link training). This is to make sure the bandwidth sent to DIG BE won't be
+		 * bigger than what the link and/or DIG BE can handle. VBID[6]/CompressedStream_flag
+		 * will be automatically set at a later time when the video is enabled
+		 * (DP_VID_STREAM_EN = 1).
+		 */
+		if (pipe_ctx->stream->timing.flags.DSC) {
+			if (dc_is_dp_signal(pipe_ctx->stream->signal) ||
+					dc_is_virtual_signal(pipe_ctx->stream->signal))
+				dp_set_dsc_enable(pipe_ctx, true);
+		}
+
 		status = enable_link(state, pipe_ctx);
 
 		if (status != DC_OK) {
@@ -3067,11 +3079,6 @@ void core_link_enable_stream(
 					CONTROLLER_DP_TEST_PATTERN_VIDEOMODE,
 					COLOR_DEPTH_UNDEFINED);
 
-		if (pipe_ctx->stream->timing.flags.DSC) {
-			if (dc_is_dp_signal(pipe_ctx->stream->signal) ||
-					dc_is_virtual_signal(pipe_ctx->stream->signal))
-				dp_set_dsc_enable(pipe_ctx, true);
-		}
 		dc->hwss.enable_stream(pipe_ctx);
 
 		/* Set DPS PPS SDP (AKA "info frames") */
-- 
2.26.0