On Tuesday 19 May 2009 17:01:27 Grant Grundler wrote: > On Tue, May 19, 2009 at 9:22 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > I've reviewed the first bit and it looks fine (so far to me). > Two related bugs: > 1) dma_alloc_coherent() is not respecting the coherent_dma_mask field > in device.h:struct device. Hmm, I've taken that function unchanged from powerpc. I guess that means that powerpc is broken here as well, right? > 2) dma_map_single() is not respecting dma_mask in struct pci_dev (and > pointer from struct device). What should it do with the mask? All the architectures I've looked at as well as arch/parisc/kernel/pci-dma.c ignore it. Should dma_map_* just fail in case of an address exceeding dma_mask? > > +/** > > + * dma_alloc_coherent - allocate consistent memory for DMA > > + * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices > > + * @size: required memory size > > + * @handle: bus-specific DMA address > > + * > > + * Allocate some uncached, unbuffered memory for a device for > > + * performing DMA. This function allocates pages, and will > > + * return the CPU-viewed address, and sets @handle to be the > > + * device-viewed address. > > Key here is the DMA is coherent, bi-directional, and the DMA address fit in > the coherent_dma_mask. "uncached/unbuffered" is one way of doing this and > is how we've implemented "DMA coherency" on parisc platforms that don't > have an IOMMU (which all have PA1.1 CPUs) - see arch/parisc/kernel/pci-dma.c All the architectures I've looked at come with their own version of _alloc_coherent that works in similar ways to allocate an uncached mapping. Now that you mention this, I realize that there is a bug on cris, which after my patch either has two conflicting implementations of dma_{alloc,free}_coherent, or is missing the dma_coherent_dev() function that is hidden inside of the same #ifdef. The one in arch/cris/arch-v32/drivers/pci/dma.c does seem to be correct though. Arnd <>< -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html