PSYCHO_IOMMU_TAG
tag[i] = upa_readq(base + PSYCHO_IOMMU_TAG+off);
upa_writeq(0, base + PSYCHO_IOMMU_TAG + off);
upa_writeq(0, pbm->controller_regs + PSYCHO_IOMMU_TAG + off);
iommu->iommu_tags = pbm->controller_regs + PSYCHO_IOMMU_TAG;