OTG and mini-a cable

Hi all!

I've a problem on the OTG port..
I have a mini-a <=> mini-b cable (i bought it on ebay) and when i try
to link it between the OTG and my self powered hub nothing works..

I tried to echo host > /sys/devices/platform/musb_hdrc/mode but the
file doesn't exist and return me an error..
I tried to modprobe g_zero but return me that none device is linked..

I have a C3 rev..

Another problem is that the serial is only in output (i tried the same
cable on an other device and it works perfectly!).. the only way to
use u-boot in input/output is via OTG..

Thanks a lot for the replies

Luca