Power Mangement on MPC8540

Hi all,
I have got u-boot-1.1.4 on MPC8540 board.I'm supposed
to put the processor in nap mode for power mangement.I have enabled the doze mode bit initially in the power mangement register which is in u-boot-1.1.4/include/asm-ppc/immap_85xx.h,but i couldnt find any change during the execution.i have disabled the unused interfaces to reduce the power,is there any code for doing putting processor in nap mode and doing power mangement? can any one help me out of this.

Thanks in advance
Revathy