1. openwrt sdk下编译uboot（添加usb端口功能）
在ehci-ra.c的ehci_hcd_init中加入MT7620_ASIC_BOARD定义：
MT7620#usbreset
(Re)startUSB...
USB:inusb_lowlevel_init
Mediatek/_length16
Register1111NbrPorts1
USBEHCI1.00
scanningbusfordevices...2USBDevice(s)found
scanningbusforstoragedevices...1StorageDevice(s)found
MT7620#usbinfo
1:Hub,USBRevision0.2
-u-bootEHCIHostController
-Class:Hub
-PacketSize:64Configurations:1
-Vendor:0x0000Proct0x0000Version0.1
Configuration:1
-Interfaces:1SelfPowered0mA
Interface:0
-AlternateSettings0,Endpoints:1
-ClassHub
-
2:MassStorage,USBRevision2.0
-HPUSB2.0Flash00CCCBB99999
-Class:(fromInterface)MassStorage
-PacketSize:64Configurations:1
-Vendor:0x0204Proct0x6025Version1.0
Configuration:1
-Interfaces:1BusPowered100mA
Interface:0
-AlternateSettings0,Endpoints:2
-ClassMassStorage,Transp.SCSI,Bulkonly
-Endpoint1OutBulkMaxPacket512
-Endpoint1InBulkMaxPacket512