Messages in this thread | | | Date | Thu, 23 May 2002 16:24:25 -0700 | From | William Jhun <> | Subject | Possible discrepancy regarding streaming DMA mappings in DMA-mapping.txt? |
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In the explanation of streaming DMA mappings and holding onto a mapping for multiple DMA operations, the file Documentation/DMA-mapping.txt (line 507) says the following:
If you need to use the same streaming DMA region multiple times and touch the data in between the DMA transfers, just map it with pci_map_{single,sg}, and after each DMA transfer call either:
pci_dma_sync_single(dev, dma_handle, size, direction);
or:
pci_dma_sync_sg(dev, sglist, nents, direction);
as appropriate.
However, shouldn't pci_dma_sync_*() be called *before* each PCI_DMA_TODEVICE DMA transfer (after the CPU write, of course) and *after* each PCI_DMA_FROMDEVICE DMA transfer (before CPU access)? And, of course, before and after a "bidirectional" DMA, if appropriate.
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