Re: [linux-pm] [PATCH 2/4] ACPI hibernate: Add a mechanism to save/restore ACPI NVS memory

Rafael J. Wysocki
2008-10-26T12:18:57Z

On Sunday, 26 of October 2008, Pavel Machek wrote:
> Hi!
>
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> >
> > ACPI hibernate: Add a mechanism to save/restore ACPI NVS memory
> >
> > According to the ACPI Specification 3.0b, Section 15.3.2,
> > "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." For this reason, implement a mechanism allowing us to save
> > the NVS memory during hibernation and to restore it during the
> > subsequent resume.
> >
> > Based on a patch by Zhang Rui.
> >
> > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> > Cc: Zhang Rui <rui.zhang@intel.com>
> > ---
> > drivers/acpi/sleep/main.c | 50 ++++++++++++++++---
> > include/linux/suspend.h | 13 ++++
> > kernel/power/swsusp.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 177 insertions(+), 7 deletions(-)
> >
>
>
> > @@ -387,8 +410,21 @@ static int acpi_hibernation_begin_old(vo
> > {
> > int error = acpi_sleep_prepare(ACPI_STATE_S4);
> >
> > + if (!error) {
> > + error = hibernate_nvs_alloc();
> > + if (!error)
> > + acpi_target_sleep_state = ACPI_STATE_S4;
> > + }
> > + return error;
> > +}
>
> You can chain this without nesting...
>
> If sleep_prepare() succeeds but nvs_alloc() fails, you should undo
> sleep_prepare here, right?

No. acpi_hibernation_finish() will undo it anyway.

> > #else /* CONFIG_HIBERNATION */
> > static inline int swsusp_page_is_forbidden(struct page *p) { return 0; }
> > static inline void swsusp_set_page_free(struct page *p) {}
> > @@ -241,6 +246,14 @@ static inline void swsusp_unset_page_fre
> > static inline void hibernation_set_ops(struct platform_hibernation_ops *ops) {}
> > static inline int hibernate(void) { return -ENOSYS; }
> > static inline bool system_entering_hibernation(void) { return false; }
> > +static inline int hibernate_nvs_register(unsigned long a, unsigned long b)
> > +{
> > + return 0;
> > +}
> > +static inline int hibernate_nvs_alloc(void) { return 0; }
> > +static inline void hibernate_nvs_free(void) {}
> > +static inline void hibernate_nvs_save(void) {}
> > +static inline void hibernate_nvs_restore(void) {}
> > #endif /* CONFIG_HIBERNATION */
>
> Can someone call these for !hibernation case?

Not at the moment, but why not to add them?

> Should they fake success if they do call them?
>
>
> > Index: linux-2.6/kernel/power/swsusp.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/power/swsusp.c
> > +++ linux-2.6/kernel/power/swsusp.c
> > @@ -262,3 +262,124 @@ int swsusp_shrink_memory(void)
> >
> > return 0;
> > }
> > +
> > +/*
> > + * Platforms, like ACPI, may want us to save some memory used by them during
> > + * hibernation and to restore the contents of this memory during the subsequent
> > + * resume. The code below implements a mechanism allowing us to do that.
> > + */
> > +
> > +struct nvs_page {
> > + unsigned long phys_start;
> > + unsigned int size;
> > + void *kaddr;
> > + void *data;
> > + struct list_head node;
> > +};
>
> Maybe separate nvs.c file would be good? I believe this _is_ acpi
> specific, altrough in theory it may not be.

No, I don't think so. The patch is correct IMO.

Thanks,
Rafael