Devicetree

APX and EFI Devicetree for Surface RT.

Please be careful with random device trees. They could contain wrong power management settings which could destroy your board.

APX vs UEFI

Why do we need 2 different devicetrees for the same device?

APX can use the full potential of the device. Therefore APX can boot with the full devicetree which enables all currently supported features.

UEFI Firmware on the other hand blocks access to some power related features like PMIC regulators, L2 Cache and Dynamic Voltage Frequency Scaling. Therefore UEFI devicetree only removes features from the APX devicetree and only adds features which are currently UEFI exclusive. Furthermore the UEFI devicetree provides fixed regulators which in place of the PMIC regulators which are needed by other features. (e.g. µSD voltage switching from 3V3 to 1V8)