USB Support in U-boot for AM1806

Hello,

We are working on AM1806 processor with the BSP provided by TI . U-Boot's version is 2011.09. We have a NAND flash memory of 128Mb and 64Mb of external RAM.We need to provide field up gradability of firmware , using USB interface.

We want to understand all the  possible options in U-BOOT, to upgrade firmware over USB interface –

1. USB with virtual COM port (USB CDC class) ?
2. USB Device Firmware Upgrade (USB DFU class) ?
3. Virtual Ethernet over USB ?

Please provide further details in this regard.

Thanks and Regards,

Subrahmanyam.