[U-Boot] usbtty using i.MX6

Hello,

I'd like to know if someone has succeed in using usbtty with i.MX6. I am interested in using it for one board but been not succed, it seems:

/home/otavio/hacking/u-boot/drivers/serial/usbtty.c:553: undefined reference to `udc_init' drivers/serial/built-in.o: In function `usbtty_init_instances': /home/otavio/hacking/u-boot/drivers/serial/usbtty.c:686: undefined reference to `udc_setup_ep' /home/otavio/hacking/u-boot/drivers/serial/usbtty.c:708: undefined reference to `urb_link_init' /home/otavio/hacking/u-boot/drivers/serial/usbtty.c:709: undefined reference to `urb_link_init' /home/otavio/hacking/u-boot/drivers/serial/usbtty.c:710: undefined reference to `urb_link_init ...

Does someone got it working?