OTX_CPT_PF_VFX_MBOXX
mbx.msg = readq(cpt->reg_base + OTX_CPT_PF_VFX_MBOXX(vf, 0));
mbx.data = readq(cpt->reg_base + OTX_CPT_PF_VFX_MBOXX(vf, 1));
writeq(mbx->data, cpt->reg_base + OTX_CPT_PF_VFX_MBOXX(vf, 1));
writeq(mbx->msg, cpt->reg_base + OTX_CPT_PF_VFX_MBOXX(vf, 0));