On 3 October 2016 at 12:08, Peter Ujfalusi <peter.ujfalusi@xxxxxx> wrote: > What happens if you set ACNT to 2? content of dma descriptor after edma transfer for various combinations of destination offset and length (ACNT): 10 11 12 13 ff ff ff ff ff ff ff ff ff ff ff ff (off=0, len=1..4) 10 11 12 13 14 15 16 17 ff ff ff ff ff ff ff ff (off=0, len=5..8) 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f (off=0, len=9..16) 00 00 00 10 ff ff ff ff ff ff ff ff ff ff ff ff (off=3, len=1) 00 00 00 10 11 12 13 10 ff ff ff ff ff ff ff ff (off=3, len=2..4) 00 00 00 10 11 12 13 14 ff ff ff ff ff ff ff ff (off=3, len=5) 00 00 00 10 11 12 13 14 15 16 17 10 11 12 13 14 (off=3, len=6..8) 00 00 00 10 11 12 13 14 15 16 17 18 19 1a 1b 1c (off=3, len=9..13) ff ff ff ff 00 00 00 10 ff ff ff ff ff ff ff ff (off=7, len=1) 00 00 00 00 00 00 00 10 11 12 13 10 11 12 13 10 (off=7, len=2) > There is no alignment restriction in eDMA. Yes and no. It supports arbitrary alignment, but the way in which it implemented this is not compatible with all targets. This is mostly something to beware of since a transfer may seem aligned if you consider only the target and not edma. > There might be restriction on the L3/L4 boundary for the ethernet Nope, L3 error logs show the transfers already have these sizes when they traverse the L3. It might be possible that it's due to the interfacing of edma to the L3, I can't really make that distinction. > How did you set up the DMA to do this? Can you paste the relevant code > snippets which does the request of the DMA channel, set up for the transfer, etc? Not easily. I use an old DM814x-based prototype board which is running a baremetal forth system I wrote which includes an edma-based memcpy command. It's extremely convenient for experimenting directly with hardware, which is why I still use it for such purposes even though we abandoned the DM814x. Matthijs -- 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
