Hello, On Friday, August 12, 2011 2:53 PM Arnd Bergmann wrote: > On Friday 12 August 2011, Marek Szyprowski wrote: > > > > From: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > > > > Steal memory from the kernel to provide coherent DMA memory to drivers. > > This avoids the problem with multiple mappings with differing attributes > > on later CPUs. > > > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > > [m.szyprowski: rebased onto 3.1-rc1] > > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > > Hi Marek, > > Is this the same patch that Russell had to revert because it didn't > work on some of the older machines, in particular those using > dmabounce? Yes. > I thought that our discussion ended with the plan to use this only > for ARMv6+ (which has a problem with double mapping) but not on ARMv5 > and below (which don't have this problem but might need dmabounce). Ok, my fault. I've forgot to mention that this patch was almost ready during Linaro meeting, but I didn't manage to post it that time. Of course it doesn't fulfill all the agreements from that discussion. I was only unsure if we should care about the case where CMA is not enabled for ARMv6+ or not. This patch was prepared in assumption that dma_alloc_coherent should work in both cases - with and without CMA. Now I assume that for ARMv6+ the CMA should be enabled unconditionally. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>