Novena power characterization

A power draw of 106 mA @ 12V was observed on multiple boards during suspend. Other i.MX6 boards report much lower current consumption, for example 40 mA @ 5V. In order to determine the sources of current drain, components are selectively depopulated and current draw is measured.

For this test, components are removed and then the board is booted. The board is running linux-3.16-rc4. The serial port is set as a wakeup source, although the difference in current draw is negligible when the serial port is not set as a wakeup source, or when the serial cable is detached.

The shell script that performe the suspend is as follows:

echo enabled > /sys/devices/soc0/soc/2100000.aips-bus/21e8000.serial/tty/ttymxc1/power/wakeup echo mem > /sys/power/state
 * 1) !/bin/sh

The board is awakened by sending any character out the debug serial port