Update: after more suspend/resume cycles it turned out that Intel Idle Driver is not to blame. Unless SpeedStep is disabled in BIOS the laptop does not realiabily resume on battery power. Since SpeedStep is about P-states rather than C-states; could someone write an experimental patch which would set P-states to a fixed value during S3 resume process, in other words something that would cause the system to behave as if SpeedStep was disabled during S3 resume?
Update: after more suspend/resume cycles it turned out that Intel Idle Driver is not to blame. Unless SpeedStep is disabled in BIOS the laptop does not realiabily resume on battery power. Since SpeedStep is about P-states rather than C-states; could someone write an experimental patch which would set P-states to a fixed value during S3 resume process, in other words something that would cause the system to behave as if SpeedStep was disabled during S3 resume?