Use ARM wait-for-interrupt (WFI) instruction instead of nop loop?

[satoshinm]

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0360e/CHDEEIJB.html

WFI (Wait For Interrupt) makes the processor suspend execution (Clock is stopped) until one of the following events take place:

An IRQ interrupt

An FIQ interrupt

A Debug Entry request made to the processor.