On Mon, 13 Jul 2009 21:17:21 -0500 Becky Bruce <beckyb@xxxxxxxxxxxxxxxxxxx> wrote: > > On Jul 9, 2009, at 8:04 PM, FUJITA Tomonori wrote: > > > swiotlb_bus_to_virt is unncessary; we can use swiotlb_bus_to_phys and > > phys_to_virt instead. > > phys_to_virt (also, virt_to_phys) is invalid for highmem addresses on > ppc. In most of the uses in this file, it doesn't matter, as the > iotlb buffers themselves are alloc'd out of lowmem, Right, > but the > dma_mark_clean() calls could happen on a highmem addr. Currently, on > powerpc, dma_mark_clean() doesn't do anything, so it isn't a > functional problem. Oops, I overlooked this. However, as you said, this is not a problem with the current code. > I'm fine with the bulk of this patch, because in > reality, if I need to do something with a virtual address of a highmem > page, I have to get a kmap for the page. So the existing > swiotlb_bus_to_virt isn't really helping. > > What is dma_mark_clean used for? Could it be made to take a paddr, > and let the implementation deal with making sure there's a valid vaddr > for the actual "clean" operation? I think that it's IA64's optimization (it's a NULL function on X86 like POWERPC). It's defined in arch/ia64/mm/init.c. Looks like POWERPC could use this optimization, I guess. dma_mark_clean() just modifies the page flag (what it needs is struct page) so I think that we can make it take a paddr. > I'd also like to see a comment with swiotlb_virt_to_bus() that notes > that it should only be called on addresses in lowmem. Ok, I'll do. Thanks, -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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