The iProc host controller allows only a subset of physical address space as
target of inbound PCI memory transaction addresses.
PCI device memory transactions targeting memory regions that are not
allowed for inbound transactions in the host controller are rejected by the
host controller and cannot reach the upstream buses.
The firmware device tree description defines the DMA ranges that are
addressable by devices DMA transactions; parse the device tree dma-ranges
property and add its ranges to the PCI host bridge dma_ranges list; the
iova_reserve_pci_windows() call executed at iommu_dma_init_domain() will
reserve the IOVA address ranges that are not addressable (ie memory holes
in the dma-ranges set) so that they are not allocated to PCI devices for
DMA transfers.
All allowed address ranges are listed in the dma-ranges DT parameter. For
example: