On Wed, 2008-06-11 at 04:21 -0400, Len Brown wrote: > On Wed, 11 Jun 2008, Huang, Ying wrote: > > On Tue, 2008-06-10 at 14:01 -0400, Len Brown wrote: > > > > > > On Tue, 10 Jun 2008, Huang, Ying wrote: > > > > > > > This patch implements devices state save/restore before after kexec. > > > > > > > > > > > > This patch together with features in kexec_jump patch can be used for > > > > following: > > > > > > > > - A simple hibernation implementation without ACPI support. You can > > > > kexec a hibernating kernel, save the memory image of original system > > > > and shutdown the system. When resuming, you restore the memory image > > > > of original system via ordinary kexec load then jump back. > > > > > > What part of ACPI's role in hibernation are you trying to avoid > > > 1. enabling wake devices > > > 2. removing power from the system > > > 3. something else? > > > > ACPI S5 is used instead of S4 for this simple hibernation > > implementation. That is, before creating the hibernation image, the ACPI > > _PTS is not executed, devices are not put into low power state and wake > > devices are not enabled. After creating the hibernation image, the image > > is saved to disk and system is shutdown (go to S5). When resuming from > > hibernated image, ACPI _BFS and _WAK are not executed too. > > Doesn't that resume the devices and their drivers into an unknown state? device_suspend(PMSG_FREEZE) and device_power_down(PMSG_FREEZE) are called before hibernation; device_power_up(PMSG_RESTORE) and device_resume(PMSG_RESTORE) are called after restore. The new hibernation/restore device driver callbacks introduced by Rafael is used. So I think the device/driver state will be saved/restored properly. It is planed to support ACPI S4 in the future. But I think a hibernation scheme without ACPI may be useful in some situation too. Best Regards, Huang Ying _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
