[U-Boot] usb host problem

[wu yufan]

hello all
           I am working on access files from USB disk . The u-boot has
implementing a mass storage operation with USB OHCI. I have added the
porting code. All things seems right except MMU.When
the MMU is closed,the result is right.But if I turn on the MMU,the returned
message is not right. I think maybe the MMU has affected USB host,even I
assigned HCCA in no-cached area.
         What should I do?Does anybody can give me some suggestion?Thanks in
advance!
         My Regards
         zzwuyu