de85711ee1
Each call to the FreeBSD bge_start() routine the transmit producer pointer index from the chip mailbox register BGE_MBX_TX_HOST_PROD0_LO. The local copy of that value is then updated by bge_encap() as bge_encap() encapsulates packets in the Tx ring. If bge_encap() succeds in encpuslating one or more packets, bge_start() tells the chip to start sending the newly-encinitiates writes the new value back to the chip mailbox register. However, comparison of the Linux drivers (Broadcom-supplied and open-source tg3.c) and to the OpenSolaris driver confirms that register BGE_MBX_TX_HOST_PROD0_LO is write-only to software. Thus, we can just keep a copy in the softc, and eliminate the (expensive) PCI register write on each call to bge_start(). ``Make it so''.