1 files changed, 28 insertions, 8 deletions

diff --git a/include/linux/pm.h b/include/linux/pm.h
index d915d0345fa1..72c0fe098a27 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -93,13 +93,23 @@ typedef struct pm_message {
  *      been registered) to recover from the race condition.
  *      This method is executed for all kinds of suspend transitions and is
  *      followed by one of the suspend callbacks: @suspend(), @freeze(), or
- *      @poweroff().  The PM core executes subsystem-level @prepare() for all
- *      devices before starting to invoke suspend callbacks for any of them, so
- *      generally devices may be assumed to be functional or to respond to
- *      runtime resume requests while @prepare() is being executed.  However,
- *      device drivers may NOT assume anything about the availability of user
- *      space at that time and it is NOT valid to request firmware from within
- *      @prepare() (it's too late to do that).  It also is NOT valid to allocate
+ *      @poweroff().  If the transition is a suspend to memory or standby (that
+ *      is, not related to hibernation), the return value of @prepare() may be
+ *      used to indicate to the PM core to leave the device in runtime suspend
+ *      if applicable.  Namely, if @prepare() returns a positive number, the PM
+ *      core will understand that as a declaration that the device appears to be
+ *      runtime-suspended and it may be left in that state during the entire
+ *      transition and during the subsequent resume if all of its descendants
+ *      are left in runtime suspend too.  If that happens, @complete() will be
+ *      executed directly after @prepare() and it must ensure the proper
+ *      functioning of the device after the system resume.
+ *      The PM core executes subsystem-level @prepare() for all devices before
+ *      starting to invoke suspend callbacks for any of them, so generally
+ *      devices may be assumed to be functional or to respond to runtime resume
+ *      requests while @prepare() is being executed.  However, device drivers
+ *      may NOT assume anything about the availability of user space at that
+ *      time and it is NOT valid to request firmware from within @prepare()
+ *      (it's too late to do that).  It also is NOT valid to allocate
  *      substantial amounts of memory from @prepare() in the GFP_KERNEL mode.
  *      [To work around these limitations, drivers may register suspend and
  *      hibernation notifiers to be executed before the freezing of tasks.]
@@ -112,7 +122,16 @@ typedef struct pm_message {
  *      of the other devices that the PM core has unsuccessfully attempted to
  *      suspend earlier).
  *      The PM core executes subsystem-level @complete() after it has executed
- *      the appropriate resume callbacks for all devices.
+ *      the appropriate resume callbacks for all devices.  If the corresponding
+ *      @prepare() at the beginning of the suspend transition returned a
+ *      positive number and the device was left in runtime suspend (without
+ *      executing any suspend and resume callbacks for it), @complete() will be
+ *      the only callback executed for the device during resume.  In that case,
+ *      @complete() must be prepared to do whatever is necessary to ensure the
+ *      proper functioning of the device after the system resume.  To this end,
+ *      @complete() can check the power.direct_complete flag of the device to
+ *      learn whether (unset) or not (set) the previous suspend and resume
+ *      callbacks have been executed for it.
  *
  * @suspend: Executed before putting the system into a sleep state in which the
  *      contents of main memory are preserved.  The exact action to perform
@@ -546,6 +565,7 @@ struct dev_pm_info {
         bool                    is_late_suspended:1;
         bool                    ignore_children:1;
         bool                    early_init:1;   /* Owned by the PM core */
+        bool                    direct_complete:1;      /* Owned by the PM core */
         spinlock_t              lock;
 #ifdef CONFIG_PM_SLEEP
         struct list_head        entry;