Messages in this thread | | | Subject | Re: [Question] devm_kmalloc() for DMA ? | From | Lars-Peter Clausen <> | Date | Wed, 8 Mar 2017 21:44:17 +0100 |
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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.
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