[PATCH 11/18] drm/amd/display: Fix possible underflow for displays with large vblank

[Tom Chung]

From: Daniel Miess <daniel.mi...@amd.com>

[Why]
Underflow observed when using a display with a large vblank region
and low refresh rate

[How]
Simplify calculation of vblank_nom

Increase value for VBlankNomDefaultUS to 800us

Fixed a null pointer from previous commit of this change

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlaus...@amd.com>
Acked-by: Tom Chung <chiahsuan.ch...@amd.com>
Signed-off-by: Daniel Miess <daniel.mi...@amd.com>
---
 .../amd/display/dc/dml/dcn314/dcn314_fpu.c    | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dml/dcn314/dcn314_fpu.c 
b/drivers/gpu/drm/amd/display/dc/dml/dcn314/dcn314_fpu.c
index 1d00eb9e73c6..554152371eb5 100644
--- a/drivers/gpu/drm/amd/display/dc/dml/dcn314/dcn314_fpu.c
+++ b/drivers/gpu/drm/amd/display/dc/dml/dcn314/dcn314_fpu.c
@@ -33,7 +33,7 @@
 #include "dml/display_mode_vba.h"
 
 struct _vcs_dpi_ip_params_st dcn3_14_ip = {
-       .VBlankNomDefaultUS = 668,
+       .VBlankNomDefaultUS = 800,
        .gpuvm_enable = 1,
        .gpuvm_max_page_table_levels = 1,
        .hostvm_enable = 1,
@@ -286,7 +286,7 @@ int dcn314_populate_dml_pipes_from_context_fpu(struct dc 
*dc, struct dc_state *c
        struct resource_context *res_ctx = &context->res_ctx;
        struct pipe_ctx *pipe;
        bool upscaled = false;
-       bool isFreesyncVideo = false;
+       const unsigned int max_allowed_vblank_nom = 1023;
 
        dc_assert_fp_enabled();
 
@@ -300,16 +300,11 @@ int dcn314_populate_dml_pipes_from_context_fpu(struct dc 
*dc, struct dc_state *c
                pipe = &res_ctx->pipe_ctx[i];
                timing = &pipe->stream->timing;
 
-               isFreesyncVideo = pipe->stream->adjust.v_total_max == 
pipe->stream->adjust.v_total_min;
-               isFreesyncVideo = isFreesyncVideo && 
pipe->stream->adjust.v_total_min > timing->v_total;
-
-               if (!isFreesyncVideo) {
-                       pipes[pipe_cnt].pipe.dest.vblank_nom =
-                               dcn3_14_ip.VBlankNomDefaultUS / 
(timing->h_total / (timing->pix_clk_100hz / 10000.0));
-               } else {
-                       pipes[pipe_cnt].pipe.dest.vtotal = 
pipe->stream->adjust.v_total_min;
-                       pipes[pipe_cnt].pipe.dest.vblank_nom = timing->v_total 
- pipes[pipe_cnt].pipe.dest.vactive;
-               }
+               pipes[pipe_cnt].pipe.dest.vtotal = 
pipe->stream->adjust.v_total_min;
+               pipes[pipe_cnt].pipe.dest.vblank_nom = timing->v_total - 
pipes[pipe_cnt].pipe.dest.vactive;
+               pipes[pipe_cnt].pipe.dest.vblank_nom = 
min(pipes[pipe_cnt].pipe.dest.vblank_nom, dcn3_14_ip.VBlankNomDefaultUS);
+               pipes[pipe_cnt].pipe.dest.vblank_nom = 
max(pipes[pipe_cnt].pipe.dest.vblank_nom, timing->v_sync_width);
+               pipes[pipe_cnt].pipe.dest.vblank_nom = 
min(pipes[pipe_cnt].pipe.dest.vblank_nom, max_allowed_vblank_nom);
 
                if (pipe->plane_state &&
                                (pipe->plane_state->src_rect.height < 
pipe->plane_state->dst_rect.height ||
-- 
2.25.1