[RFC PATCH v4] ARM hibernation/suspend-to-disk support
Russell King - ARM Linux
linux at arm.linux.org.uk
Thu Jun 9 12:50:29 EDT 2011
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.
More information about the linux-arm-kernel