[PATCH v6 4/5] PM: hibernate: add new api pm_hibernate_is_recovering()

[Samuel Zhang <guoqing.zhang@amd.com>]

dev_pm_ops.thaw() is called in following cases:
* normal case: after hibernation image has been created.
* error case 1: creation of a hibernation image has failed.
* error case 2: restoration from a hibernation image has failed.

For normal case, it is called mainly for resume storage devices for
saving the hibernation image. Other devices that are not involved
in the image saving do not need to resume the device. But since there's
no api to know which case thaw() is called, device drivers can't
conditionally resume device in thaw().

The new pm_hibernate_is_recovering() is such a api to query if thaw() is
called in normal case.

Signed-off-by: Samuel Zhang <guoqing.zhang@amd.com>
---
 drivers/base/power/main.c | 14 ++++++++++++++
 include/linux/suspend.h   |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 24ebe7a635a7..c4817b379230 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -66,6 +66,20 @@ static pm_message_t pm_transition;
 static DEFINE_MUTEX(async_wip_mtx);
 static int async_error;
 
+/**
+ * pm_hibernate_is_recovering - if recovering from hibernate due to error.
+ *
+ * Used to query if dev_pm_ops.thaw() is called for normal hibernation case or
+ * recovering from some error.
+ *
+ * Return: true for error case, false for normal case.
+ */
+bool pm_hibernate_is_recovering(void)
+{
+	return pm_transition.event == PM_EVENT_RECOVER;
+}
+EXPORT_SYMBOL_GPL(pm_hibernate_is_recovering);
+
 static const char *pm_verb(int event)
 {
 	switch (event) {
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 6a3f92098872..d11a124b7a91 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -426,6 +426,8 @@ int is_hibernate_resume_dev(dev_t dev);
 static inline int is_hibernate_resume_dev(dev_t dev) { return 0; }
 #endif
 
+bool pm_hibernate_is_recovering(void);
+
 /* Hibernation and suspend events */
 #define PM_HIBERNATION_PREPARE	0x0001 /* Going to hibernate */
 #define PM_POST_HIBERNATION	0x0002 /* Hibernation finished */
-- 
2.43.5