[RFC PATCH v4] ARM hibernation/suspend-to-disk support
frank.hofmann at tomtom.com
Thu Jun 9 12:53:53 EDT 2011
On Thu, 9 Jun 2011, Russell King - ARM Linux wrote:
> On Tue, Jun 07, 2011 at 05:48:17PM +0100, Frank Hofmann wrote:
>> There are a few dependencies this patch brings in:
>> * due to the use of cpu_suspend / cpu_resume, it'll only apply as-is
>> to kernels no older than f6b0fa02e8b0708d17d631afce456524eadf87ff,
>> where Russell King introduced the generic interface.
>> Patching these into older kernels is a little work.
>> * it temporarily uses swapper_pg_dir and establishes 1:1 mappings there
>> for a MMU-off transition, which is necessary before resume.
>> In order to tear these down afterwards, identity_mapping_del() needs
>> to be called; for some reason that's #ifdef CONFIG_SMP ...
>> * it needs to "catch" sleep_save_sp after cpu_suspend() so that resume
>> can be provided with the proper starting point.
>> This requires an ENTRY(sleep_save_sp) in arch/arm/kernel/sleep.S so
>> that the symbol becomes public.
>> * it assumes cpu_reset will disable the MMU. cpu_v6_reset/cpu_v7_reset
>> are currently not doing so (amongst some other minor chip types).
>> * there's kind of a circular dependency between CONFIG_HIBERNATION and
>> CONFIG_PM_SLEEP, on ARM. The latter is necessary so that cpu_suspend
>> and cpu_resume are compiled in, but it cannot be selected via
>> ARCH_HIBERNATION_POSSIBLE because CONFIG_PM_SLEEP depends on
>> CONFIG_HIBERNATION_INTERFACE - selected by CONFIG_HIBERNATION.
> Another issue is that it uses PHYS_OFFSET in assembly code which is not
> permissible with P2V patching.
Would calling something like:
unsigned long __swsusp_arch_get_vpoffset(void *addr)
return (virt_to_phys(addr) - (unsigned long)addr);
from the assembly be ok ?
(That's what I've gone for at the moment to address this; a generic func
somewhere to query for this would obviously be ok as well)
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