drivers/pm: PM: Decrease the power state in the reverse order. Since the child driver need power off before parent driver.

drivers/power/pm.h

@@ -154,12 +154,12 @@ struct pm_global_s
 
   sem_t regsem;
 
-  /* registry is a singly-linked list of registered power management
+  /* registry is a doubly-linked list of registered power management
    * callback structures.  To ensure mutually exclusive access, this list
    * must be locked by calling pm_lock() before it is accessed.
    */
 
-  sq_queue_t registry;
+  dq_queue_t registry;
 };
 
 /****************************************************************************

drivers/power/pm_changestate.c

@@ -76,14 +76,16 @@
 
 static int pm_prepall(int domain, enum pm_state_e newstate)
 {
-  FAR sq_entry_t *entry;
+  FAR dq_entry_t *entry;
   int ret = OK;
 
-  /* Visit each registered callback structure. */
+  if (newstate <= g_pmglobals.domain[domain].state)
+    {
+      /* Visit each registered callback structure in normal order. */
 
-  for (entry = sq_peek(&g_pmglobals.registry);
+      for (entry = dq_peek(&g_pmglobals.registry);
            entry && ret == OK;
-       entry = sq_next(entry))
+           entry = dq_next(entry))
         {
           /* Is the prepare callback supported? */
 
@@ -95,6 +97,26 @@ static int pm_prepall(int domain, enum pm_state_e newstate)
               ret = cb->prepare(cb, domain, newstate);
             }
         }
+    }
+  else
+    {
+      /* Visit each registered callback structure in reverse order. */
+
+      for (entry = dq_tail(&g_pmglobals.registry);
+           entry && ret == OK;
+           entry = dq_prev(entry))
+        {
+          /* Is the prepare callback supported? */
+
+          FAR struct pm_callback_s *cb = (FAR struct pm_callback_s *)entry;
+          if (cb->prepare)
+            {
+              /* Yes.. prepare the driver */
+
+              ret = cb->prepare(cb, domain, newstate);
+            }
+        }
+    }
 
   return ret;
 }
@@ -120,11 +142,13 @@ static int pm_prepall(int domain, enum pm_state_e newstate)
 
 static inline void pm_changeall(int domain, enum pm_state_e newstate)
 {
-  FAR sq_entry_t *entry;
+  FAR dq_entry_t *entry;
 
-  /* Visit each registered callback structure. */
+if (newstate <= g_pmglobals.domain[domain].state)
+    {
+      /* Visit each registered callback structure in normal order. */
 
-  for (entry = sq_peek(&g_pmglobals.registry); entry; entry = sq_next(entry))
+      for (entry = dq_peek(&g_pmglobals.registry); entry; entry = dq_next(entry))
         {
           /* Is the notification callback supported? */
 
@@ -136,6 +160,24 @@ static inline void pm_changeall(int domain, enum pm_state_e newstate)
               cb->notify(cb, domain, newstate);
             }
         }
+    }
+  else
+    {
+      /* Visit each registered callback structure in reverse order. */
+
+    for (entry = dq_tail(&g_pmglobals.registry); entry; entry = dq_prev(entry))
+        {
+          /* Is the notification callback supported? */
+
+          FAR struct pm_callback_s *cb = (FAR struct pm_callback_s *)entry;
+          if (cb->notify)
+            {
+              /* Yes.. notify the driver */
+
+              cb->notify(cb, domain, newstate);
+            }
+        }
+    }
 }
 
 /****************************************************************************

drivers/power/pm_initialize.c

@@ -86,7 +86,7 @@ void pm_initialize(void)
    * data structure here.
    */
 
-  sq_init(&g_pmglobals.registry);
+  dq_init(&g_pmglobals.registry);
   nxsem_init(&g_pmglobals.regsem, 0, 1);
 }
 

drivers/power/pm_register.c

@@ -79,7 +79,7 @@ int pm_register(FAR struct pm_callback_s *callbacks)
   ret = pm_lock();
   if (ret == OK)
     {
-      sq_addlast(&callbacks->entry, &g_pmglobals.registry);
+      dq_addlast(&callbacks->entry, &g_pmglobals.registry);
       pm_unlock();
     }
 

drivers/power/pm_unregister.c

@@ -79,7 +79,7 @@ int pm_unregister(FAR struct pm_callback_s *callbacks)
   ret = pm_lock();
   if (ret == OK)
     {
-      sq_rem(&callbacks->entry, &g_pmglobals.registry);
+      dq_rem(&callbacks->entry, &g_pmglobals.registry);
       pm_unlock();
     }
 

include/nuttx/power/pm.h

@@ -277,7 +277,7 @@ enum pm_state_e
 
 struct pm_callback_s
 {
-  struct sq_entry_s entry;   /* Supports a singly linked list */
+  struct dq_entry_s entry;   /* Supports a doubly linked list */
 
   /**************************************************************************
    * Name: prepare