On Fri, 10 Oct 2008 16:45:08 -0600 Grant Grundler <grundler@xxxxxxxxxxxxxxxx> wrote: > On Fri, Oct 10, 2008 at 11:40:56AM +0900, FUJITA Tomonori wrote: > > IIRC, except for one SGI architecture, coherent_dma_mask is > > meaningless, dma_mask is always equal to coherent_dma_mask. > > Not correct. Several PCI-X devices can only do 32-bit DMA to control > data but can do 64-bit DMA for payload data. I don't have the list off > the top of my head but that is the origin of coherent DMA mask. Thanks. I misunderstood coherent_dma_mask. I needed to read several old mails (posted in 2002 and 2003) in ia64 mailing list. > > Lots of > > IOMMU implementations ignore coherent_dma_mask and use dma_mask for > > alloc_coherent(). > > That sounds like a bug. And I don't think it's "lots". Maybe it's not "lots" but seems that only IA64 and x86 non-hardware IOMMU code (pci-nommu.c and GART) use coherent_dma_mask for alloc_coherent. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
