Messages in this thread | | | From | Alex Feinman <> | Date | Mon, 20 Aug 2018 13:39:06 -0700 | Subject | Contiguous DMA buffer view for a custom device (Intel/x86) |
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Good morning. I have a custom PCI device that needs to fill memory buffers of up to 16MB in size. For various reasons I would like to avoid implementing scatter-gather support in the device and would much rather prefer a contiguous buffer view instead. The buffers are allocated using dma_alloc_coherent or dma_alloc_attrs (as I don't necessarily need coherent access)
This is on a custom Skylake/Kaby Lake platform
It is my understanding (possibly incorrect) that a) The contiguous memory space available to subsystems like videobuf2-dma-contig is limited and I won't be likely to be able tp allocate say 4 16MB contiguous buffers reliably b) IOMMU can solve this problem for me by providing a device-specific contiguous view of a fragmented physical memory allocation c) In order to enable IOMMU do the above, I need to allocate DRHDs and DMARs in BIOS initialization (I build my own BIOS)
Please, let me know if I am on the right track? Of course I realize that implementing SGDMA would be the best option, but short of that and blocking out some physical memory on boot, what are my options?
Are there any pointers of how exactly achieve this (implementation I could peruse, articles and whatnot)?
Best regards
Alex Feinman ReplyForward
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