[PATCH] drm/amd/display: Keep linebuffer pixel depth at 30bpp for DCE-11.0.

[Mario Kleiner]

Testing on AMD Carizzo with DCE-11.0 display engine showed that
it doesn't like a 36 bpp linebuffer very much. The display just
showed a solid green.

Testing on RavenRidge DCN-1.0, Polaris11 with DCE-11.2 and Kabini
with DCE-8.3 did not expose any problems, so for now only revert
to 30 bpp linebuffer depth on asics with DCE-11.0 display engine.

Reported-by: Tom StDenis <Tom.StDenis at amd.com>
Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
Cc: Alex Deucher <alexander.deucher at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_resource.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

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 b2ee3cd77b4e..a4f1ae8930a4 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
@@ -1213,9 +1213,16 @@ bool resource_build_scaling_params(struct pipe_ctx *pipe_ctx)
 	 * on certain displays, such as the Sharp 4k. 36bpp is needed
 	 * to support SURFACE_PIXEL_FORMAT_GRPH_ARGB16161616 and
 	 * SURFACE_PIXEL_FORMAT_GRPH_ABGR16161616 with actual > 10 bpc
-	 * precision on at least DCN display engines.
+	 * precision on at least DCN display engines. However, at least
+	 * Carrizo with DCE_VERSION_11_0 does not like 36 bpp lb depth,
+	 * so use only 30 bpp on DCE_VERSION_11_0. Testing with DCE 11.2 and 8.3
+	 * did not show such problems, so this seems to be the exception.
 	 */
-	pipe_ctx->plane_res.scl_data.lb_params.depth = LB_PIXEL_DEPTH_36BPP;
+	if (plane_state->ctx->dce_version != DCE_VERSION_11_0)
+		pipe_ctx->plane_res.scl_data.lb_params.depth = LB_PIXEL_DEPTH_36BPP;
+	else
+		pipe_ctx->plane_res.scl_data.lb_params.depth = LB_PIXEL_DEPTH_30BPP;
+
 	pipe_ctx->plane_res.scl_data.lb_params.alpha_en = plane_state->per_pixel_alpha;
 
 	pipe_ctx->plane_res.scl_data.recout.x += timing->h_border_left;
-- 
2.25.1