In following text, khibernation is the abbreviation of "kexec based hibernation". 1. Kexec/kdump and ACPI With Linux kernel 2.6.23-rc6-mm1 + khibernation patches on my IBM T42, khibernation works well with ACPI. That is, the following is possible with ACPI enabled. a. Boot kernel A with ACPI on b. Put devices in quiescent and low power state c. Kexec a new kernel B with ACPI on d. Jump back to kernel A I think it should be a standard feature that the kexeced kernel can be booted properly with devices been put in low power state. Because, if the dynamic power management is enabled, some idle devices will be put into low power state even in G0, when a crash dump is triggered, the crash dump kernel should be booted properly even with devices been put in low power state. If this not supported, the crash dump can not work on system with dynamic power management on. 2. Khibernation and ACPI Khibernation can work with ACPI even without feature above, because image-writing kernel with initramfs can be booted independent of device state. The scheme is as follow: a. Boot kernel A with ACPI on b. Put all devices in quiescent and low power state c. Execute _PTS of ACPI d. Kexec a new kernel B with ACPI on. The root filesystem is initramfs, so that, the only devices needed by kernel B is timer. e. In kernel B, put needed devices back to normal state. f. Write memory image of kernel A out g. Put all devices in quiescent and low power state h. Execute acpi_enter_sleep_state(ACPI_STATE_S4) Any comment is welcome. Best Regards, Huang Ying _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
