Omap4 Power Management: Online/Offline CPU and their leakage currents

Hi,

I am working on Omap4460 processor on Samsung Galaxy Nexus using Linux kernel 3.0.8. I have three questions -

1] In file cpuidle44xx.c, the C4 state is defined as "C4 - CPU0 OFF + CPU1 OFF + MPU CSWR + CORE OSWR". Does CPUx OFF means a logical or physical offline of the CPU? (Logical OFF is that the CPU can't execute any more instructions but it is not hot plugged from the power source, instead it is removed from kernel's visibility, Is my understanding correct?)

2] Also, writing a zero to cpu1/online makes the CPU1 go offline (is this offline a logical or physical?). This is checked by looking at the tasks (user applications) migrating from CPU1 to CPU0. Also from /proc/interrupts it is clear that the CPU1 doesn't handle any more interrupts. However, when I do the same on CPU0, it doesn't allow me to put CPU0 to offline even when it is idle. Does this mean that CPU0 can't put in offline mode or is it because of the user's UART interrupt wakes-up CPU0  automatically?

3] From ARM Cortex A9 manual which is used in OMAP 4460 processor.. it is said that "Wait for Interrupt mode disables all the clocks of a Cortex-A9 processor, while keeping its logic powered up. This reduces the power drawn to the static leakage current." If WFI reduces the static leakage current, can I say that the static power consumption caused by the leakage currents is Zero or almost zero in case of C4 state (CPU's OFF mode) ?

Reference: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0407e/CACGJGEE.html

Thanks a ton in advance for clearing these doubts and your time.

Best Regards

Siva Penke