drm/amd/display: Added negative check for vertical line start.

	In case of vstartup happens before vsync, set vertical line
	start to 0.

Signed-off-by: Yongqiang Sun <yongqiang.sun@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_timing_generator.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_timing_generator.c
index 405f595..2d3dd9a 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_timing_generator.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_timing_generator.c
@@ -118,7 +118,7 @@ static void tgn10_program_timing(
        uint32_t start_point = 0;
        uint32_t field_num = 0;
        uint32_t h_div_2;
-       uint32_t vertial_line_start;
+       int32_t vertical_line_start;
 
        struct dcn10_timing_generator *tgn10 = DCN10TG_FROM_TG(tg);
 
@@ -216,9 +216,13 @@ static void tgn10_program_timing(
        /* Use OTG_VERTICAL_INTERRUPT2 replace VUPDATE interrupt,
         * program the reg for interrupt postition.
         */
-       vertial_line_start = asic_blank_end - tg->dlg_otg_param.vstartup_start + 1;
+       vertical_line_start = asic_blank_end - tg->dlg_otg_param.vstartup_start + 1;
+       if (vertical_line_start < 0) {
+               ASSERT(0);
+               vertical_line_start = 0;
+       }
        REG_SET(OTG_VERTICAL_INTERRUPT2_POSITION, 0,
-                       OTG_VERTICAL_INTERRUPT2_LINE_START, vertial_line_start);
+                       OTG_VERTICAL_INTERRUPT2_LINE_START, vertical_line_start);
 
        /* v_sync polarity */
        v_sync_polarity = patched_crtc_timing.flags.VSYNC_POSITIVE_POLARITY ?