The following series adds support to EDMA driver to enable DMA of scatter-gather lists of arbitrary length, but still make use of only a certain MAX number of slots at a time for a given channel. Thus free-ing up the rest of the slots to other slaves/channels. With this there is no need for slave drivers to query the EDMA driver about how much is the MAX it can send at a time as done in [1]. Drivers can send SG lists of any number of entries to DMA. Reference discussion at [2]. Tested omap-aes and omap_hsmmc drivers with different MAX number of slots, even just 1. In the case where it is 1, only 1-slot is used to DMA an entire scatter list of arbitrary length. Since this series touches EDMA private API code also shared with davinci-pcm, playback of a 16-bit 44.1KHz audio file with davinci-pcm has been tested. Sample test run with 1 vs 16 (MAX number of slots/SG) in omap-aes driver: MAX slots = 1: (128 bit key, 8192 byte blocks): 1266 operations in 1 seconds (10371072 bytes) MAX slots = 16: (128 bit key, 8192 byte blocks): 1601 operations in 1 seconds (13115392 bytes) Note: For the above test, 8K buffer is mapped into SG list of size 2 so only 2 slots are required. So beyond size 2, there will not be any noticeable performance improvement. But using 1 slot is even managed by just DMA'ing 1 SG entry at a time. [1] https://lkml.org/lkml/2013/7/18/432 [2] http://marc.info/?l=linux-omap&m=137416733628831&w=2 Joel Fernandes (9): dma: edma: Setup parameters to DMA MAX_NR_SG at a time dma: edma: Write out and handle MAX_NR_SG at a given time ARM: edma: Add function to manually trigger an EDMA channel dma: edma: Find missed events and issue them dma: edma: Leave linked to Null slot instead of DUMMY slot dma: edma: Detect null slot errors and handle them correctly ARM: edma: Don't clear EMR of channel in edma_stop dma: edma: Link to dummy slot only for last SG list split dma: edma: remove limits on number of slots arch/arm/common/edma.c | 22 ++++- drivers/dma/edma.c | 157 +++++++++++++++++++++++++++--------- include/linux/platform_data/edma.h | 2 + 3 files changed, 142 insertions(+), 39 deletions(-) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
