Methods, apparatus, and systems for securely providing multiple wake-up time options for PCI Express (PCIe) devices. Under one approach, Vendor Define Messages (VDMs) are exchanged between a host application layer in a host and a device application layer in a PCIe endpoint device coupled to the host via a PCIe link to effect changes to the L1.2 Substate exit time of a PCIe device. Under another approach, Vendor-Specific Extended Capability (VSEC) structures are exchanged between a host application layer and a device application layer to effect the changes. The VDMs and VSEC structures may also be used to enable a host to read Tpower_on capability information defining power modes supported by a PCIe device. Additionally, VSEC implementations are provided that implement VSEC components in the PCIe device transaction layer or the PCIe device application layer.