apart from this you need to be aware of your cache type used in system On Sat, Feb 8, 2014 at 8:41 PM, Miles MH Chen <orca.chen@xxxxxxxxx> wrote: > Hi, > > dma_map_xxx / dma_unmap_xxx pair are used to do cache coherency. > see Documentation/DMA-API.txt. > > dma_map_xxx: "Maps a piece of processor virtual memory so it can be accessed > by the device and returns the physical handle of the memory." > dma_unmap_xxx: "Unmaps the region previously mapped. All the parameters > passed in must be identical to those passed in (and returned) by the mapping > API." > > Assuming you are doing DMA_TO_DEVICE synchronization: > > cpu accesses buffer > dma_map_xxx (after this point, cpu cannot touch the buffer) > device accesses buffer > > > device accesses buffer > dma_unmap_xxx (after this point, device cannot touch the buffer) > cpu accesses buffer > > Regards, > MH > > > On Sat, Feb 8, 2014 at 4:16 PM, m silverstri > <michael.j.silverstri@xxxxxxxxx> wrote: >> >> Hi, >> >> I create DMA buffer in my kernel driver. >> I would like to know what is cache coherency guidelines for DMA >> buffer referred by this post? >> >> http://stackoverflow.com/questions/5564326/linux-kernel-device-driver-to-dma-into-kernel-space >> >> Both my kernel driver and HW writes to the DMA buffer. I wnat to know >> how to make sure cache coherency. >> >> Thank you. >> >> _______________________________________________ >> Kernelnewbies mailing list >> Kernelnewbies@xxxxxxxxxxxxxxxxx >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
