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ERR005783: Ethernet Overruns with short frames

Question asked by kal on Jun 25, 2013

I'm seeing Ethernet overruns on the iMX6 which I suspect are due to ERR005783, described in the errata as "When the MAC receives shorter frames (size 64 bytes) at a rate exceeding the average line-rate burst traffic of 400 Mbps the DMA is able to absorb, the receiver may drop incoming frames before a Pause frame is issued."


The workaround then goes on to imply that it it applies up to packet sizes of 800 bytes. So is it the case that you can expect overruns if your Ethernet frame sizes are between 64 and 800 bytes, or does it only apply to frame sizes of up to 64 bytes?



I am using the Boundary 4.0.0 kernel to take advantage of FEC patches that already improved the reliability considerably (by treating truncated frames as overruns instead of passing them up the stack). Unfortunately it seems that either these truncated frames or ERR005783 are causing fairly significant packet loss, which might be tolerable on TCP connections but not for protocols without flow control.


Any advice much appreciated.