Re: [PATCH 2/4] ACPI hibernate: Add a mechanism to save/restore ACPI NVS memory (rev. 2)

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Hi.

On Thu, 2008-10-23 at 07:47 +0200, Rafael J. Wysocki wrote:
> On Thursday, 23 of October 2008, Nigel Cunningham wrote:
> > On Thu, 2008-10-23 at 01:08 +0200, Rafael J. Wysocki wrote:
> > > On Thursday, 23 of October 2008, Nigel Cunningham wrote:
> > > > On Wed, 2008-10-22 at 22:52 +0200, Rafael J. Wysocki wrote:
> > > > > From: Rafael J. Wysocki <rjw@xxxxxxx>
> [--snip--]
> > > > > +/**
> > > > > + *	hibernate_nvs_save - save NVS memory regions
> > > > > + */
> > > > > +void hibernate_nvs_save(void)
> > > > > +{
> > > > > +	struct nvs_page *entry;
> > > > > +
> > > > > +	printk(KERN_INFO "PM: Saving platform NVS memory\n");
> > > > > +
> > > > > +	list_for_each_entry(entry, &nvs_list, node)
> > > > > +		if (entry->data) {
> > > > > +			entry->kaddr = ioremap(entry->phys_start, entry->size);
> > > > > +			memcpy(entry->data, entry->kaddr, entry->size);
> > > > 
> > > > Why not unmap here? (I know you're delaying the unmap until the free,
> > > > but it's probably clearer to map and unmap each time the memory is
> > > > accessed (ie in restore too).
> > > 
> > > Ah, this one is tricky.  We cannot unmap from atomic context. :-)
> > 
> > Maybe a comment then, lest someone get the same idea in future and be as
> > ignorant as me? :)
> 
> Well, I was considering to add one, now changed the kerneldoc comment to
> mention that.

Terrific. Thanks.

> Please find updated patch below.
> 
> ---
> From: Rafael J. Wysocki <rjw@xxxxxxx>
> 
> ACPI hibernate: Add a mechanism to save/restore ACPI NVS memory (rev. 2)
> 
> 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@xxxxxxx>
> Acked-by: Nigel Cunningham <nigel@xxxxxxxxxxxx>
> Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
> ---
>  drivers/acpi/sleep/main.c |   50 +++++++++++++++---
>  include/linux/suspend.h   |   13 ++++
>  kernel/power/swsusp.c     |  124 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 180 insertions(+), 7 deletions(-)
> 
> Index: linux-2.6/drivers/acpi/sleep/main.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/sleep/main.c
> +++ linux-2.6/drivers/acpi/sleep/main.c
> @@ -321,8 +321,23 @@ void __init acpi_no_s4_hw_signature(void
>  
>  static int acpi_hibernation_begin(void)
>  {
> -	acpi_target_sleep_state = ACPI_STATE_S4;
> -	return 0;
> +	int error;
> +
> +	error = hibernate_nvs_alloc();
> +	if (!error)
> +		acpi_target_sleep_state = ACPI_STATE_S4;
> +
> +	return error;
> +}
> +
> +static int acpi_hibernation_pre_snapshot(void)
> +{
> +	int error = acpi_pm_prepare();
> +
> +	if (!error)
> +		hibernate_nvs_save();
> +
> +	return error;
>  }
>  
>  static int acpi_hibernation_enter(void)
> @@ -343,6 +358,12 @@ static int acpi_hibernation_enter(void)
>  	return ACPI_SUCCESS(status) ? 0 : -EFAULT;
>  }
>  
> +static void acpi_hibernation_finish(void)
> +{
> +	hibernate_nvs_free();
> +	acpi_pm_finish();
> +}
> +
>  static void acpi_hibernation_leave(void)
>  {
>  	/*
> @@ -358,6 +379,8 @@ static void acpi_hibernation_leave(void)
>  			"cannot resume!\n");
>  		panic("ACPI S4 hardware signature mismatch");
>  	}
> +	/* Restore the NVS memory area */
> +	hibernate_nvs_restore();
>  }
>  
>  static void acpi_pm_enable_gpes(void)
> @@ -368,8 +391,8 @@ static void acpi_pm_enable_gpes(void)
>  static struct platform_hibernation_ops acpi_hibernation_ops = {
>  	.begin = acpi_hibernation_begin,
>  	.end = acpi_pm_end,
> -	.pre_snapshot = acpi_pm_prepare,
> -	.finish = acpi_pm_finish,
> +	.pre_snapshot = acpi_hibernation_pre_snapshot,
> +	.finish = acpi_hibernation_finish,
>  	.prepare = acpi_pm_prepare,
>  	.enter = acpi_hibernation_enter,
>  	.leave = acpi_hibernation_leave,
> @@ -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;
> +}
> +
> +static int acpi_hibernation_pre_snapshot_old(void)
> +{
> +	int error = acpi_pm_disable_gpes();
> +
>  	if (!error)
> -		acpi_target_sleep_state = ACPI_STATE_S4;
> +		hibernate_nvs_save();
> +
>  	return error;
>  }
>  
> @@ -399,8 +435,8 @@ static int acpi_hibernation_begin_old(vo
>  static struct platform_hibernation_ops acpi_hibernation_ops_old = {
>  	.begin = acpi_hibernation_begin_old,
>  	.end = acpi_pm_end,
> -	.pre_snapshot = acpi_pm_disable_gpes,
> -	.finish = acpi_pm_finish,
> +	.pre_snapshot = acpi_hibernation_pre_snapshot_old,
> +	.finish = acpi_hibernation_finish,
>  	.prepare = acpi_pm_disable_gpes,
>  	.enter = acpi_hibernation_enter,
>  	.leave = acpi_hibernation_leave,
> Index: linux-2.6/include/linux/suspend.h
> ===================================================================
> --- linux-2.6.orig/include/linux/suspend.h
> +++ linux-2.6/include/linux/suspend.h
> @@ -233,6 +233,11 @@ extern unsigned long get_safe_page(gfp_t
>  extern void hibernation_set_ops(struct platform_hibernation_ops *ops);
>  extern int hibernate(void);
>  extern bool system_entering_hibernation(void);
> +extern int hibernate_nvs_register(unsigned long start, unsigned long size);
> +extern int hibernate_nvs_alloc(void);
> +extern void hibernate_nvs_free(void);
> +extern void hibernate_nvs_save(void);
> +extern void hibernate_nvs_restore(void);
>  #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 */
>  
>  #ifdef CONFIG_PM_SLEEP
> 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 +262,127 @@ int swsusp_shrink_memory(void)
>  
>  	return 0;
>  }
> +
> +/*
> + * Platforms, like ACPI, may want us to save some memory used by them during

Both commas should be removed from the line above.

> + * 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;
> +};
> +
> +static LIST_HEAD(nvs_list);
> +
> +/**
> + *	hibernate_nvs_register - register platform NVS memory region to save
> + *	@start - physical address of the region
> + *	@size - size of the region
> + *
> + *	The NVS region need not be page-aligned (both ends) and we arrange
> + *	things so that the data from page-aligned addresses in this region will
> + *	be copied into separate RAM pages.
> + */
> +int hibernate_nvs_register(unsigned long start, unsigned long size)
> +{
> +	struct nvs_page *entry, *next;
> +
> +	while (size > 0) {
> +		unsigned int nr_bytes;
> +
> +		entry = kzalloc(sizeof(struct nvs_page), GFP_KERNEL);
> +		if (!entry)
> +			goto Error;
> +
> +		list_add_tail(&entry->node, &nvs_list);
> +		entry->phys_start = start;
> +		nr_bytes = PAGE_SIZE - (start & ~PAGE_MASK);
> +		entry->size = (size < nr_bytes) ? size : nr_bytes;
> +
> +		start += entry->size;
> +		size -= entry->size;
> +	}
> +	return 0;
> +
> + Error:
> +	list_for_each_entry_safe(entry, next, &nvs_list, node) {
> +		list_del(&entry->node);
> +		kfree(entry);
> +	}
> +	return -ENOMEM;
> +}
> +
> +/**
> + *	hibernate_nvs_free - free data pages allocated for saving NVS regions
> + *
> + *	It is allowed to call this function many times in a row.

"This function may safely be called multiple times." .... maybe just do
without the comment?

> + */
> +void hibernate_nvs_free(void)
> +{
> +	struct nvs_page *entry;
> +
> +	list_for_each_entry(entry, &nvs_list, node)
> +		if (entry->data) {
> +			free_page((unsigned long)entry->data);
> +			entry->data = NULL;
> +			if (entry->kaddr) {
> +				iounmap(entry->kaddr);
> +				entry->kaddr = NULL;
> +			}
> +		}
> +}
> +
> +/**
> + *	hibernate_nvs_alloc - allocate memory necessary for saving NVS regions
> + */
> +int hibernate_nvs_alloc(void)
> +{
> +	struct nvs_page *entry;
> +
> +	list_for_each_entry(entry, &nvs_list, node) {
> +		entry->data = (void *)__get_free_page(GFP_KERNEL);
> +		if (!entry->data) {
> +			hibernate_nvs_free();
> +			return -ENOMEM;
> +		}
> +	}
> +	return 0;
> +}
> +
> +/**
> + *	hibernate_nvs_save - save NVS memory regions
> + */
> +void hibernate_nvs_save(void)
> +{
> +	struct nvs_page *entry;
> +
> +	printk(KERN_INFO "PM: Saving platform NVS memory\n");
> +
> +	list_for_each_entry(entry, &nvs_list, node)
> +		if (entry->data) {
> +			entry->kaddr = ioremap(entry->phys_start, entry->size);
> +			memcpy(entry->data, entry->kaddr, entry->size);
> +		}
> +}
> +
> +/**
> + *	hibernate_nvs_restore - restore NVS memory regions
> + *
> + *	This function is going to be called with interrupts disabled, so it
> + *	cannot iounmap the virtual addresses used to access the NVS region.
> + */
> +void hibernate_nvs_restore(void)
> +{
> +	struct nvs_page *entry;
> +
> +	printk(KERN_INFO "PM: Restoring platform NVS memory\n");
> +
> +	list_for_each_entry(entry, &nvs_list, node)
> +		if (entry->data)
> +			memcpy(entry->kaddr, entry->data, entry->size);
> +}

Regards,

Nigel

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