Hi, The following series with the final patch will add support for sDMA Linked List transfer support. Linked List is supported by sDMA in OMAP3630+ (OMAP4/5, dra7 family). If the descriptor load feature is present we can create the descriptors for each SG beforehand and let sDMA to walk them through. This way the number of sDMA interrupts the kernel need to handle will drop dramatically. I have gathered some numbers to show the difference. Booting up the board with filesystem on SD card for example: # cat /proc/interrupts | grep dma W/o LinkedList support: 27: 4436 0 WUGEN 13 Level omap-dma-engine Same board/filesystem with this patch: 27: 1027 0 WUGEN 13 Level omap-dma-engine Or copying files from SD card to eMCC: # du -h /usr 2.1G /usr/ # find /usr/ -type f | wc -l 232001 # cp -r /usr/* /mnt/emmc/tmp/ W/o LinkedList we see ~761069 DMA interrupts. With LinkedList support it is down to ~269314 DMA interrupts. With the decreased DMA interrupt number the CPU load is dropping significantly as well. The series depends on the interleaved transfer support patch I have sent couple of days ago: https://lkml.org/lkml/2016/7/12/216 Regards, Peter --- Peter Ujfalusi (7): dmaengine: omap-dma: Simplify omap_dma_start_sg parameter list dmaengine: omap-dma: Complete the cookie first on transfer completion dmaengine: omap-dma: Simplify omap_dma_callback dmaengine: omap-dma: Dynamically allocate memory for lch_map dmaengine: omap-dma: Add more debug information when freeing channel dmaengine: omap-dma: Use pointer to omap_sg in slave_sg setup's loop dmaengine: omap-dma: Support for LinkedList transfer of slave_sg drivers/dma/omap-dma.c | 234 +++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 207 insertions(+), 27 deletions(-) -- 2.9.1 -- 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
