RADEON_CRTC_V_TOTAL
if( v_total > V_2PIX( RADEON_CRTC_V_TOTAL ) ) {
v_total = V_2PIX( RADEON_CRTC_V_TOTAL );
((mode->timing.v_total - 1) & RADEON_CRTC_V_TOTAL)
a = (r & RADEON_CRTC_V_TOTAL);