There is an errata on the GigE controller that is related to the Rx path. The errata describes conditions whereby the Rx path of GigE becomes completely unresponsive with heavy Rx traffic of small sized packets. The condition occurrence is rare; however a software reset of the Rx logic in the controller is required when such a condition occurs. This API must be called periodically (approximately every 100 milliseconds using a timer or thread) from user applications to ensure that the Rx path never becomes unresponsive for more than 100 milliseconds.
void xemacpsif_resetrx_on_no_rxdata(struct netif *netif);