On Wed, Sep 30, 2020 at 08:10:00AM +0300, Dmitry Osipenko wrote: > 30.09.2020 03:30, Nicolin Chen пишет: > ... > > +#ifdef CONFIG_PCI > > + if (!iommu_present(&pci_bus_type)) { > > Could you please explain why this check is needed? That's referencing what's in the arm-smmu.c file, since it does not hurt to have a check.