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, 46 insertions, 10 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 47882bfa610e..fa3b43b7206d 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -54,7 +54,8 @@ static struct hibernation_ops *hibernation_ops;
 
 void hibernation_set_ops(struct hibernation_ops *ops)
 {
-        if (ops && !(ops->prepare && ops->enter && ops->finish)) {
+        if (ops && !(ops->prepare && ops->enter && ops->finish
+            && ops->pre_restore && ops->restore_cleanup)) {
                 WARN_ON(1);
                 return;
         }
@@ -92,6 +93,31 @@ static void platform_finish(int platform_mode)
 }
 
 /**
+ *      platform_pre_restore - prepare the platform for the restoration from a
+ *      hibernation image.  If the restore fails after this function has been
+ *      called, platform_restore_cleanup() must be called.
+ */
+
+static int platform_pre_restore(int platform_mode)
+{
+        return (platform_mode && hibernation_ops) ?
+                hibernation_ops->pre_restore() : 0;
+}
+
+/**
+ *      platform_restore_cleanup - switch the platform to the normal mode of
+ *      operation after a failing restore.  If platform_pre_restore() has been
+ *      called before the failing restore, this function must be called too,
+ *      regardless of the result of platform_pre_restore().
+ */
+
+static void platform_restore_cleanup(int platform_mode)
+{
+        if (platform_mode && hibernation_ops)
+                hibernation_ops->restore_cleanup();
+}
+
+/**
  *      hibernation_snapshot - quiesce devices and create the hibernation
  *      snapshot image.
  *      @platform_mode - if set, use the platform driver, if available, to
@@ -141,11 +167,13 @@ int hibernation_snapshot(int platform_mode)
 /**
  *      hibernation_restore - quiesce devices and restore the hibernation
  *      snapshot image.  If successful, control returns in hibernation_snaphot()
+ *      @platform_mode - if set, use the platform driver, if available, to
+ *                       prepare the platform frimware for the transition.
  *
  *      Must be called with pm_mutex held
  */
 
-int hibernation_restore(void)
+int hibernation_restore(int platform_mode)
 {
         int error;
 
@@ -155,11 +183,14 @@ int hibernation_restore(void)
         if (error)
                 goto Finish;
 
-        error = disable_nonboot_cpus();
-        if (!error)
-                error = swsusp_resume();
-
-        enable_nonboot_cpus();
+        error = platform_pre_restore(platform_mode);
+        if (!error) {
+                error = disable_nonboot_cpus();
+                if (!error)
+                        error = swsusp_resume();
+                enable_nonboot_cpus();
+        }
+        platform_restore_cleanup(platform_mode);
  Finish:
         device_resume();
         resume_console();
@@ -260,8 +291,12 @@ int hibernate(void)
         }
         error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
         if (in_suspend && !error) {
+                unsigned int flags = 0;
+
+                if (hibernation_mode == HIBERNATION_PLATFORM)
+                        flags |= SF_PLATFORM_MODE;
                 pr_debug("PM: writing image.\n");
-                error = swsusp_write();
+                error = swsusp_write(flags);
                 swsusp_free();
                 if (!error)
                         power_down();
@@ -295,6 +330,7 @@ int hibernate(void)
 static int software_resume(void)
 {
         int error;
+        unsigned int flags;
 
         mutex_lock(&pm_mutex);
         if (!swsusp_resume_device) {
@@ -342,9 +378,9 @@ static int software_resume(void)
 
         pr_debug("PM: Reading swsusp image.\n");
 
-        error = swsusp_read();
+        error = swsusp_read(&flags);
         if (!error)
-                hibernation_restore();
+                hibernation_restore(flags & SF_PLATFORM_MODE);
 
         printk(KERN_ERR "PM: Restore failed, recovering.\n");
         swsusp_free();