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Visitor seandresen
Registered: ‎01-23-2017

AXI DMA v7.1, SG multi channel, receive length?



I'm using AXI DMA v7.1, configured as SG multi channel. The 2-D function is not needed, so VSIZE=1, Stride=0 and HSIZE=max_buffer_length in the S2MM descriptors. Reception works, but how/where can I see how many bytes were received? I was expecting HSIZE to be updated to the actual number of bytes received. According to this post from 2014, it is not possible to retrieve this number: https://forums.xilinx.com/t5/Networking-and-Connectivity/axi-dma-receive-frame-length-in-multi-channel-mode/m-p/472542#M6071. Is this still the case today? I'm having a hard time understanding that only (predetermined) fixed size packets are relevant for multi channel applications, and that all sizes are known in advance. Let's assume that a S2MM channel is connected to a network interface. Frame sizes could be "anything". Without multi channel, the size is reflected in the descriptor (S2MM_APP4.RX_Length), but the S2MM multi channel descriptor lacks this field. Any suggestions? Thanks in advance.




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