... > +#ifdef CONFIG_PCI > + if (!iommu_present(&pci_bus_type)) { In the previous reply you said that you're borrowing this check from the arm-smmu driver, but arm-smmu also has a similar check for platform_bus_type, while Tegra SMMU driver doesn't have it. Hence I'm objecting the necessity of having this check. Please give a rationale for having this check in the code. And please note that cargo cult isn't a rationale to me.