On Mon, Mar 27, 2017 at 8:16 PM, Rob Herring <robh@xxxxxxxxxx> wrote: > On Sat, Mar 25, 2017 at 12:31 AM, Oza Pawandeep <oza.oza@xxxxxxxxxxxx> wrote: >> it is possible that PCI device supports 64-bit DMA addressing, >> and thus it's driver sets device's dma_mask to DMA_BIT_MASK(64), >> however PCI host bridge may have limitations on the inbound >> transaction addressing. As an example, consider NVME SSD device >> connected to iproc-PCIe controller. >> >> Currently, the IOMMU DMA ops only considers PCI device dma_mask >> when allocating an IOVA. This is particularly problematic on >> ARM/ARM64 SOCs where the IOMMU (i.e. SMMU) translates IOVA to >> PA for in-bound transactions only after PCI Host has forwarded >> these transactions on SOC IO bus. This means on such ARM/ARM64 >> SOCs the IOVA of in-bound transactions has to honor the addressing >> restrictions of the PCI Host. >> >> current pcie frmework and of framework integration assumes dma-ranges >> in a way where memory-mapped devices define their dma-ranges. >> dma-ranges: (child-bus-address, parent-bus-address, length). >> >> but iproc based SOCs and even Rcar based SOCs has PCI world dma-ranges. >> dma-ranges = <0x43000000 0x00 0x00 0x00 0x00 0x80 0x00>; > > If you implement a common function, then I expect to see other users > converted to use it. There's also PCI hosts in arch/powerpc that parse > dma-ranges. the common function should be similar to what of_pci_get_host_bridge_resources is doing right now. it parses ranges property right now. the new function would look look following. of_pci_get_dma_ranges(struct device_node *dev, struct list_head *resources) where resources would return the dma-ranges. but right now if you see the patch, of_dma_configure calls the new function, which actually returns the largest possible size. so this new function has to be generic in a way where other PCI hosts can use it. but certainly iproc(Broadcom SOC) , rcar based SOCs can use it for sure. although having powerpc using it; is a separate exercise, since I do not have any access to other PCI hosts such as powerpc. but we can workout with them on thsi forum if required. so overall, of_pci_get_dma_ranges has to serve following 2 purposes. 1) it has to return largest possible size to of_dma_configure to generate largest possible dma_mask. 2) it also has to return resources (dma-ranges) parsed, to the users. so to address above needs of_pci_get_dma_ranges(struct device_node *dev, struct list_head *resources, u64 *size) dev -> device node. resources -> dma-ranges in allocated list. size -> highest possible size to generate possible dma_mask for of_dma_configure. let em know how this sounds. Regards, Oza.
