swsusp: introduce restore platform operations

At least on some machines it is necessary to prepare the ACPI firmware for the
restoration of the system memory state from the hibernation image if the
"platform" mode of hibernation has been used.  Namely, in that cases we need
to disable the GPEs before replacing the "boot" kernel with the "frozen"
kernel (cf.  http://bugzilla.kernel.org/show_bug.cgi?id=7887).  After the
restore they will be re-enabled by hibernation_ops->finish(), but if the
restore fails, they have to be re-enabled by the restore code explicitly.

For this purpose we can introduce two additional hibernation operations,
called pre_restore() and restore_cleanup() and call them from the restore code
path.  Still, they should be called if the "platform" mode of hibernation has
been used, so we need to pass the information about the hibernation mode from
the "frozen" kernel to the "boot" kernel in the image header.

Apparently, we can't drop the disabling of GPEs before the restore because of
Bug #7887 .   We also can't do it unconditionally, because the GPEs wouldn't
have been enabled after a successful restore if the suspend had been done in
the 'shutdown' or 'reboot' mode.

In principle we could (and probably should) unconditionally disable the GPEs
before each snapshot creation *and* before the restore, but then we'd have to
unconditionally enable them after the snapshot creation as well as after the
restore (or restore failure)   Still, for this purpose we'd need to modify
acpi_enter_sleep_state_prep() and acpi_leave_sleep_state() and we'd have to
introduce some mechanism synchronizing the disablind/enabling of the GPEs with
the device drivers' .suspend()/.resume() routines and with
disable_/enable_nonboot_cpus().   However, this would have affected the
suspend (ie.  s2ram) code as well as the hibernation, which I'd like to avoid
in this patch series.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/kernel/power/power.h b/kernel/power/power.h
index 70c378b..eab3603 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -27,7 +27,7 @@ struct swsusp_info {
 
 /* kernel/power/disk.c */
 extern int hibernation_snapshot(int platform_mode);
-extern int hibernation_restore(void);
+extern int hibernation_restore(int platform_mode);
 extern int hibernation_platform_enter(void);
 #endif
 
@@ -155,13 +155,20 @@ extern sector_t alloc_swapdev_block(int swap);
 extern void free_all_swap_pages(int swap);
 extern int swsusp_swap_in_use(void);
 
+/*
+ * Flags that can be passed from the hibernatig hernel to the "boot" kernel in
+ * the image header.
+ */
+#define SF_PLATFORM_MODE	1
+
+/* kernel/power/disk.c */
 extern int swsusp_check(void);
 extern int swsusp_shrink_memory(void);
 extern void swsusp_free(void);
 extern int swsusp_suspend(void);
 extern int swsusp_resume(void);
-extern int swsusp_read(void);
-extern int swsusp_write(void);
+extern int swsusp_read(unsigned int *flags_p);
+extern int swsusp_write(unsigned int flags);
 extern void swsusp_close(void);
 extern int suspend_enter(suspend_state_t state);