I am trying to port usb_ohci code (u-boot-1.1.3 version) from
cpu/arm920t/s3c24x0 to our chip NEC 720101 chip

and it is found that it is hanging when we run usb tree call, even though we havnot out any usb devices.

ATS1.0> usb start
(Re)start USB...
USB:   scanning bus for devices... 1 USB Devices found
ATS1.0> usb info
1: Hub, USB Revision 1.10
- OHCI Root Hub
- Class: Hub
- PacketSize: 8 Configurations: 1
- Vendor: 0x0000 Product 0x0000 Version 0.0
   Configuration: 1
   - Interfaces: 1 Self Powered 0mA
     Interface: 0
     - Alternate Settings 0, Endpoints: 1
     - Class Hub
     - Endpoint 1 In Interrupt MaxPacket 2 Interval 255ms