/* * JMC250 can't handle Tx checksum offload/TSO if frame length * is larger than its FIFO size(2K). It's also good idea to not * use jumbo frame if hardware is running at half-duplex media. * Because the jumbo frame may not fit into the Tx FIFO, * collisions make hardware fetch frame from host memory with * DMA again which in turn slows down Tx performance * significantly. */