NV_PCRTC_ENGINE_CTRL
regp->crtc_eng_ctrl = NVReadCRTC(dev, head, NV_PCRTC_ENGINE_CTRL);
NVWriteCRTC(dev, head, NV_PCRTC_ENGINE_CTRL, regp->crtc_eng_ctrl);
nvif_mask(dev, NV_PCRTC_ENGINE_CTRL + soff, NV_CRTC_FSEL_OVERLAY, NV_CRTC_FSEL_OVERLAY);
nvif_mask(dev, NV_PCRTC_ENGINE_CTRL + soff2, NV_CRTC_FSEL_OVERLAY, 0);