On Thu, Jun 20, 2013 at 12:10:04AM +0900, Inki Dae wrote: > On the other hand, the below shows how we could enhance the conventional > way with my approach (just example): > > CPU -> DMA, > ioctl(qbuf command) ioctl(streamon) > | | > | | > qbuf <- dma_buf_sync_get start streaming <- syncpoint > > dma_buf_sync_get just registers a sync buffer(dmabuf) to sync object. And > the syncpoint is performed by calling dma_buf_sync_lock(), and then DMA > accesses the sync buffer. > > And DMA -> CPU, > ioctl(dqbuf command) > | > | > dqbuf <- nothing to do > > Actual syncpoint is when DMA operation is completed (in interrupt handler): > the syncpoint is performed by calling dma_buf_sync_unlock(). > Hence, my approach is to move the syncpoints into just before dma access > as long as possible. What you've just described does *not* work on architectures such as ARMv7 which do speculative cache fetches from memory at any time that that memory is mapped with a cacheable status, and will lead to data corruption. -- 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
