On 03/08/2017 08:59 PM, Russell King - ARM Linux wrote: > On Wed, Mar 08, 2017 at 08:48:31PM +0100, Lars-Peter Clausen wrote: >> When the DMA memory is mapped for reading from the device the associated >> cachelines are invalidated without writeback. There is no guarantee that >> the changes made to the devres_node have made it to main memory yet, or >> is there? > > That is incorrect. > > Overlapping cache lines are always written back on transitions from CPU > to device ownership of the buffer (eg, dma_map_*().) On ARM. But my understanding is that this is not a universal requirement according to DMA-API.txt. It says that mappings must be cache line aligned and otherwise behavior is undefined. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
