Specialized boot path for speeding up resume from sleep state

摘要

A specialized boot path for speeding up resume from a sleep state is discussed. In a UEFI-compliant system, a specially constructed alternate firmware volume is created which contains only the code modules used during resumption from an S3 sleep state. This alternate firmware volume is copied into Random Access Memory (RAM) during a normal boot. When the system subsequently enters the S3 sleep state and then begins the resume boot process, code in the boot sequence detects it is a resume from an S3 sleep state, restores a RAM configuration and jumps execution to a Pre-EFI Initialization (PEI) core entry point in the alternate firmware volume in RAM instead of to a firmware volume in ROM. This alternate firmware volume performs specified S3 resume tasks and then returns control to the operating system.

主权项

1. A computing device-implemented method, comprising:
performing a first boot sequence for the computing device; copying an alternate firmware volume containing firmware modules used during an S3 sleep state resume sequence into Random Access Memory (RAM); storing in non-volatile memory a RAM configuration for the computing device; entering an S3 sleep state for the computing device subsequent to the completion of the first boot sequence; resuming execution of the computing device after entering the S3 sleep state by beginning a second boot sequence in response to detection of a wake event; detecting that the second boot sequence is a resumption from the S3 sleep state and restoring the RAM configuration; retrieving a previously recorded address of the alternate firmware volume, the address recorded prior to the computing device completing the entering of the S3 sleep state, and diverting the execution of the second boot sequence to a Pre-Extensible Firmware Interface Initialization (PEI) core entry point in the alternate firmware volume in RAM using the retrieved address prior to the computing device resuming an operating mode controlled by an operating system.