On Thu, 2009-08-06 at 22:59 -0700, David Xiao wrote: > The V7 speculative prefetching will then probably apply to DMA coherency > issue in general, both kernel and user space DMAs. Could this be > addressed by inside the dma_unmap_sg/single() calling dma_cache_maint() > when the direction is DMA_FROM_DEVICE/DMA_BIDIRECTIONAL, to basically > invalidate the related cache lines in case any filled by prefetching? > Assuming dma_unmap_sg/single() is called after each DMA operation is > completed. Theoretically, with speculative prefetching on ARMv7 and the FROM_DEVICE case we need to invalidate the corresponding D-cache lines both before and after the DMA transfer, i.e. in both dma_map_sg and dma_unmap_sg, otherwise there is a risk of stale data in the cache. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
