On Sun, 15 Aug 2010 09:23:28 +0100 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Sun, Aug 15, 2010 at 02:42:51PM +0900, FUJITA Tomonori wrote: > > On Sat, 14 Aug 2010 19:46:05 +0100 > > Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > > > > > On Sat, Aug 14, 2010 at 06:30:37PM +0900, FUJITA Tomonori wrote: > > > > On Fri, 13 Aug 2010 22:54:13 +0100 > > > > Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > > > > > This means that when dmabounce comes to allocate the replacement > > > > > buffer, it gets a buffer which won't be accessible to the DMA > > > > > controller > > > > > > > > Really? looks like dmabounce does nothing for coherent memory that > > > > dma_alloc_coherent() allocates. > > > > > > > > The following very hacky patch works? > > > > > > So what happens if you use a driver which uses dma_alloc_coherent() > > > directly? Should the driver really be passed memory which is > > > inaccessible to the device because its outside the host bridge PCI > > > window? > > > > I'm not sure what you mean. > > > > A driver which uses dma_alloc_coherent() directly should > > work. dma_alloc_coherent() allocates memory with GFP_DMA with that > > patch for dmabounce devices. So the driver gets the access-able > > memory. > > > > The memory that dma_alloc_coherent() returns should be always > > consistent. We can't bounce it. All we can do is returning a memory > > that a device (and its bus) can access to. > > > > Krzysztof, can you try the patch? > > Why bother when we both agree that the patch is a dirty hack? > > Come up with something cleaner first. Because this fix needs to go to stable trees too. A simple patch is better even if it's hacky. For example, we can unify dma_needs_bounce functions in arm with a clean solution, I think. But dma_needs_bounce() was changed after 2.6.35 so it would be difficult to backport a clean solution. btw, will we have more like this case? If so, I think that it's worth having a generic solution for this case instead of having the arch (arm and powerpc) specific solution. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html