drm/amd/display: Revert to old formula in set_vtg_params

[Why]
New formula + cursor change causing underflow
on certain configs

[How]
Rever to old formula

Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Reviewed-by: Yongqiang Sun <yongqiang.sun@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.c
index 17d96ec..ec0ab42 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_optc.c
@@ -299,6 +299,7 @@ void optc1_set_vtg_params(struct timing_generator *optc,
        uint32_t asic_blank_end;
        uint32_t v_init;
        uint32_t v_fp2 = 0;
+       int32_t vertical_line_start;
 
        struct optc *optc1 = DCN10TG_FROM_TG(optc);
 
@@ -315,8 +316,9 @@ void optc1_set_vtg_params(struct timing_generator *optc,
                        patched_crtc_timing.v_border_top;
 
        /* if VSTARTUP is before VSYNC, FP2 is the offset, otherwise 0 */
-       if (optc1->vstartup_start > asic_blank_end)
-               v_fp2 = optc1->vstartup_start - asic_blank_end;
+       vertical_line_start = asic_blank_end - optc1->vstartup_start + 1;
+       if (vertical_line_start < 0)
+               v_fp2 = -vertical_line_start;
 
        /* Interlace */
        if (REG(OTG_INTERLACE_CONTROL)) {