how to make /dev/random work?

[loody <miloody@gmail.com>]

Dear all:
I made linux running on Mips machine.
Right now I found the /dev/random doesn't work properly, since I use
"dd if=/dev/random of=/tmp/random.txt", it stops working.
If I use "cat /dev/random", it will not pop out anything.

Is there any setting I forget while make menuconfig or should i add
another driver for /dev/random such that I can make /dev/random work?
appreciate your help,
miloody