[U-Boot] Multiple USB controller support under Uboot

Hello,

I am using ISP156x USB PCI controller with Uboot. Right now, the code can find only 1 root hub when I use "usb inf" or "usb tree" command to check the USB tree. If I list the PCI device, it shows there are 2 OHCI and 1 EHCI host controller. Anyone knows why I have only one root hub? What shall the USB tree looks like for ISP156x USB PCI host controller? Thanks,

Mike