On Mon, 23 May 2011, Russell King - ARM Linux wrote:

> On Mon, May 23, 2011 at 02:37:19PM +0100, Frank Hofmann wrote:
>> What I've found necessary to save/restore via swsusp_arch_suspend/resume
>> are the SYSTEM_MODE and SVC_MODE registers.
>> Yesterday, I had thought that cpu_init() resets SVC_MODE sufficiently but
>> that doesn't seem to be the case, if I leave that out, resume-from-disk
>> doesn't work anymore.
>
> You will be running in SVC mode, so the SVC mode registers are your
> current register set.  At some point you need to do an effective
> "context switch" between the kernel doing the resume and the kernel
> which was running.  That involves restoring the saved register state.
>
> System mode on the other hand is unused by the kernel.
>

Ah, and I had it the other way round ... that's why. Thanks !

I've tried that, saving/restoring just CPSR/SPSR and the reg set - and 
that seems sufficient, works fine !


All this means that the basic code has again become smaller.
Attached is a new version, integrating all the feedback so far:

* save/restore only those parts of the register set that the kernel cannot
   reinitialize from scratch

* take care of FIQ disable/enable bracketing

* use traditional stmfd/ldmfd instead of push/pop

* don't rely on thread state, current->active_mm, but use global &init_mm

* dump arch_prepare_suspend (skipping ahead of Rafael's suggested fix)

* ditch the vmlinux.lds changes as they're not needed


What other outstanding things are there to address for this ?

All the best,
FrankH.