2 files changed, 26 insertions, 2 deletions

diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 0e856088db7c..5336149f831b 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -789,6 +789,16 @@ will behave normally, not taking the autosuspend delay into account.
 Similarly, if the power.use_autosuspend field isn't set then the autosuspend
 helper functions will behave just like the non-autosuspend counterparts.
 
+Under some circumstances a driver or subsystem may want to prevent a device
+from autosuspending immediately, even though the usage counter is zero and the
+autosuspend delay time has expired.  If the ->runtime_suspend() callback
+returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is
+in the future (as it normally would be if the callback invoked
+pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
+autosuspend.  The ->runtime_suspend() callback can't do this rescheduling
+itself because no suspend requests of any kind are accepted while the device is
+suspending (i.e., while the callback is running).
+
 The implementation is well suited for asynchronous use in interrupt contexts.
 However such use inevitably involves races, because the PM core can't
 synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 18ef87e525fa..124dbf60c9bf 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -293,6 +293,9 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
  * the callback was running then carry it out, otherwise send an idle
  * notification for its parent (if the suspend succeeded and both
  * ignore_children of parent->power and irq_safe of dev->power are not set).
+ * If ->runtime_suspend failed with -EAGAIN or -EBUSY, and if the RPM_AUTO
+ * flag is set and the next autosuspend-delay expiration time is in the
+ * future, schedule another autosuspend attempt.
  *
  * This function must be called under dev->power.lock with interrupts disabled.
  */
@@ -413,10 +416,21 @@ static int rpm_suspend(struct device *dev, int rpmflags)
         if (retval) {
                 __update_runtime_status(dev, RPM_ACTIVE);
                 dev->power.deferred_resume = false;
-                if (retval == -EAGAIN || retval == -EBUSY)
+                if (retval == -EAGAIN || retval == -EBUSY) {
                         dev->power.runtime_error = 0;
-                else
+
+                        /*
+                         * If the callback routine failed an autosuspend, and
+                         * if the last_busy time has been updated so that there
+                         * is a new autosuspend expiration time, automatically
+                         * reschedule another autosuspend.
+                         */
+                        if ((rpmflags & RPM_AUTO) &&
+                            pm_runtime_autosuspend_expiration(dev) != 0)
+                                goto repeat;
+                } else {
                         pm_runtime_cancel_pending(dev);
+                }
                 wake_up_all(&dev->power.wait_queue);
                 goto out;
         }