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

Pavel Machek
2008-10-26T12:09:11Z

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?

> #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? 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.
--
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