VSYNC_START_MASK
u32 vsync_start = REG_FIELD_GET(VSYNC_START_MASK, vsync) + 1;
adjusted_mode->crtc_vsync_start = REG_FIELD_GET(VSYNC_START_MASK, tmp) + 1;
#define VSYNC_START(vsync_start) REG_FIELD_PREP(VSYNC_START_MASK, (vsync_start))