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imx6d fec buffer descriptor update incoherent

Question asked by Klaus Gusenleitner on Sep 22, 2016
Latest reply on Mar 8, 2017 by Klaus Gusenleitner

Using Linux 4.8-rc3 we have some trouble with fec ethernet on our imx6 board. Our driver instrumentation in fec_main.c shows that sporadically the BD_ENET_RX_EMPTY bit in the current receive buffer descriptor state word is kept set in case of a receive interrupt. On the next frame receptions the next buffer descriptors are updated correctly. After a few seconds the BD_ENET_RX_EMPTY bit disappears and the driver continues frame rx processing.
Also, for txing frames, BD_ENET_TX_READY is kept set but the frame is on wire. I think this is the cause for the kernel warning "NETDEV WATCHDOG: eth0 (fec): transmit queue 0 timed".
Any help would be greatly appreciated.