5V and 3V3 backpower is untested

Problem environment

Host devices may be powered by the 5V and 3V3 power circuits. In some cases this power supply method is documented and depends on conditions.

Steps to reproduce

1. Refer to the schematic
2. Locate power interfaces
3. Examine connections to host

Expected result

The power supply method when backpowering connected host devices conforms to best practices and host documented conditions.

Actual result

Backpowering is untested and undocumented.

Workaround

A backpowering configuration (indication and current rating) may be written to the EEPROM data structure to build a appropriate device tree at host boot.

Severity level

This is low priority because project requirements do not state a (back) power strategy.

Partially implemented in 55b3621 to support selective (via JP7) testing.