[U-Boot] u-boot prompt on serial over usb console ttyACM0

[Sumit]

Hi,

I've serial over usb support for my board which is using usbtty class 
driver in u-boot.

When I load this u-boot on my board, after enumeration is done, it 
creates /dev/ttyACM0 on host. Now when I start another serial terminal 
with /dev/ttyACM0 it initialize the terminal but u-boot does not give 
any prompt (i.e. it does not display anything except terminal 
initialization).

I am using minicom as console terminal.

Also after enumeration is done, I do #setenv stdout 'usbtty' as well.

Any help in this regard would be really helpful.
Am I missing in configuring any thing in u-boot??

Thanks,
Sumit