On Tue, 2008-06-24 at 18:18 +0800, Rafael J. Wysocki wrote:
> On Tuesday, 24 of June 2008, Zhang Rui wrote:
> > According to the ACPI spec, ACPI NVS memory region is required to be
> > saved/restored by OS during hibernation.
> >
> > Section 15.3.2 ACPI Spec 3.0b,
> > "OSPM will call the _PTS control method some time before entering a
> sleeping state,
> > to allow the platform’s AML code to update this memory image before
> entering the
> > sleeping state. After the system awakes from an S4 state, OSPM will
> restore this memory
> > area and call the _WAK control method to enable the BIOS to reclaim
> its memory image."
> >
> > Add the mechanism to save/restore ACPI NVS memory during
> hibernation.
> >
> > Note: now Linux save ACPI NVS memory in
> acpi_hibernation_pre_snapshot, and restore it in
> > acpi_hibernation_leave. Both of these functions will be
> invoked only once during
> > the hibernate and resume.
> > Note: in Section 14.3 ACPI spec 3.0b, I only get
> > "EfiACPIMemoryNVS: The OS and loader must preserve this memory
> range in
> > the working and ACPI S1–S3 states."
> > whether we should save/restore this piece of memory is not
> cleared.
> >
> > Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
>
> Well, I know what the specification says, but we tried that in the
> past and it
> caused regressions.
Yes, Shaohua generated the prototype patches a couple of years ago.
But this is slightly different from the original one, e.g. not touching
ACPI DATA memory, saving ACPI NVS memory after _PTS and restore it
before _WAK strictly, etc.
We generate this patch set and hope it be helpful for some hibernate
specific issues.
> > +
> > +static int
> > +acpi_hibernation_notifier_cb(struct notifier_block *nb,
> > + unsigned long val, void *data)
> > +{
> > + int result = 0;
> > +
> > + switch (val) {
> > + case PM_HIBERNATION_PREPARE:
> > + result = acpi_hibernation_allocate_nvs_pages();
> > + break;
> > + case PM_POST_RESTORE: /* Failed */
> > + case PM_POST_HIBERNATION:
> > + acpi_hibernation_free_nvs_pages();
> > + }
> > + return result;
> > +}
> > +
> > +struct notifier_block acpi_hibernation_nb = {
> > + .notifier_call = acpi_hibernation_notifier_cb,
> > +};
>
> This is over the top, IMO. Please put the appropriate call into
> acpi_hibernation_begin() and create acpi_hibernation_end() with the
> call to
> acpi_hibernation_free_nvs_pages() (it must do what acpi_pm_end() does
> apart
> from this).
Pages for ACPI NVS must be allocated before swsusp_shrink_memory.
And none platform hibernation ops can be used in this case.
thanks,
rui
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