Hi, Regarding ARM hibernation / suspend-to-disk, now that the glue part of the code has "settled" it's probably time to think about the gory low-level things, what's been delegated to the __save/__restore_processor_state() hooks. Russell King did the cpu_suspend / cpu_resume cleanup in Feb/2011, http://lists.arm.linux.org.uk/lurker/message/20110211.161754.78371a42.en.html which cleansed the mach-.../ sleep code in favour of moving these things into processor type support hooks in arch/arm/mm/proc-*.S instead. The key thing here was the addition of cpu_do_suspend/cpu_do_resume hooks which save/restore state to/from a caller-supplied buffer, and then return to their callers. I.e. pure auxilliary, "no side effects" (other than, for resume, of course, what's desired). The power-down / enter-low-power parts were separated from that. >From my point of view, all platforms that use these should be able to do the cpu-specific parts of hibernation via a simple addition, say, to arch/arm/kernel/sleep.S (that's already using <asm/glue-proc.h> so cpu_do_... exists), of something like: #if defined(CONFIG_HAS_ARM_GENERIC_CPU_SUSPEND_SUPPORT) && defined(CONFIG_HIBERNATION) ENTRY(__save_processor_state) b cpu_do_suspend ENDPROC(__save_processor_state) ENTRY(__restore_processor_state) stmfd sp!,{r4-r11,lr} bl cpu_do_resume ldmfd sp!,{r4-r11,pc} ENDPROC(__restore_processor_state) #endif and "select HAS_ARM_GENERIC_CPU_SUSPEND_SUPPORT if CONFIG_PM" for the CPU architectures that compile suitable mm/proc-*.S in. That would do because the cpu_do_suspend/resume hooks perform the same CP reg save/restore operations as the "illustration patches" I've posted for OMAP3 and samsung 64xx (in fact, the latter is one of the platforms changed via Russell's patch series). >From my point of view, this assumes the following: - cpu_do_suspend() takes one argument, a virtual address of the buffer to save the state into. It is a "well-behaved" EABI-compliant func that preserves nonvolatile regs. It returns to LR. - cpu_do_resume() assumes it can clobber registers; it takes one argument, the address (not necessarily virtual) of the buffer to restore state from. The function does not depend on the MMU being OFF (could be called with the MMU on, it'll "just clobber the state"). It also returns to LR. Do these assumptions hold ? If so, then would it be ok to create a patch for 2.6.39 onwards (baselined against ARM devel-stable), along the lines just mentioned ? How would one best test something as sweeping as that ? The above suggestion still leaves a hole out for machine-specific implementations - unselect the GENERIC config and implement the hook yourself. Seems desireable ? Regarding pre-2.6.38 kernels, are there any plans to backport the cpu_suspend changes to any -stable series ? Thanks in advance for comments / suggestions / corrections, FrankH. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
