Open Source Summit + ELC Europe 2018

Debugging power management issues is traditionally done via the serial console, Android USB/ADB, or SSH eventually. Besides being tedious, it is also intrusive debugging (CPU “regular” execution flow periodically interrupted to log traces over the UART, a rather slow interface with blind windows during CPU power transitions). But there is another option: the JTAG port. Well known for deep kernel debugging, it used to be less popular for power debugging. Well, until now! JTAG port offers the only non-intrusive solution to monitor system activities. Leveraging already-available python libraries, it is now possible to monitor key power indicators (clock rates/states, power states, voltages, bus stats, etc) without altering the use-case power profile, from your host PC.

Motivations, challenges, benefits, and results will be further exposed, including a demo of a “power dashboard” application.