Robert Jarzmik <robert.jarzmik@xxxxxxx> writes: > This patch attempts to enhance the case of a transfer submitted multiple > times, and where the cost of creating the descriptors chain is not > negligible. > > This happens with big video buffers (several megabytes, ie. several > thousands of linked descriptors in one scatter-gather list). In these > cases, a video driver would want to do : > - tx = dmaengine_prep_slave_sg() > - dma_engine_submit(tx); > - dma_async_issue_pending() > - wait for video completion > - read video data (or not, skipping a frame is also possible) > - dma_engine_submit(tx) > => here, the descriptors chain recalculation will take time > => the dma coherent allocation over and over might create holes in > the dma pool, which is counter-productive. > - dma_async_issue_pending() > - etc ... > > In order to cope with this case, virt-dma is modified to prevent freeing > the descriptors upon completion if DMA_CTRL_REUSE flag is set in the > transfer. > > This patch is a respin of the former DMA_CTRL_ACK approach, which was > reverted due to a regression in audio drivers. > > Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx> > --- > Since v1: added doxygen commit to vchan_tx_desc_free Hi Vinod, Is this serie good for you or do you have remaining comments to be addressed ? Cheers. -- Robert -- 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
