RADEON_CRTC2_V_TOTAL_DISP
vbl = (RREG32(RADEON_CRTC2_V_TOTAL_DISP) &
crtc2_v_total_disp = RREG32(RADEON_CRTC2_V_TOTAL_DISP);
WREG32(RADEON_CRTC2_V_TOTAL_DISP, 0x00080001);
WREG32(RADEON_CRTC2_V_TOTAL_DISP, crtc2_v_total_disp);