I think for our purposes we want to try to use UART since we want to try to send data directly to the PRU so that we can off load as much work from the ARM processor as possible. The more that I look around the more that it seems like we should be trying to use the L3 interconnect to pass the data to a buffer in the DDR3 RAM. From there I’m not sure if the ARM processor should try to read out the data from the the DDR3 directly or if we should be trying to move data from DDR3 to the ARM’s internal 64KB with the EDMA. We don’t really need the timestamps like you did, but the main goal for us would be to offload as much work from the ARM processor as possible and to reduce the latencies for data transfer between memory regions as much as possible.
I did find some good info here: Fastes way to copy large amounts of data from pru to arm