PM: runtime: Add pm_runtime_put_autosuspend() replacement

Add __pm_runtime_put_autosuspend() that replaces
pm_runtime_put_autosuspend() for new users. The intent is to later
re-purpose pm_runtime_put_autosuspend() to also mark the device's last
busy stamp---which is what the vast majority of users actually need.

This is also described in pm_runtime_put_autosuspend() documentation.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/power/runtime_pm.rst

@@ -154,7 +154,7 @@ suspending the device are satisfied) and to queue up a suspend request for the
 device in that case.  If there is no idle callback, or if the callback returns
 0, then the PM core will attempt to carry out a runtime suspend of the device,
 also respecting devices configured for autosuspend.  In essence this means a
-call to pm_runtime_autosuspend() (do note that drivers needs to update the
+call to __pm_runtime_autosuspend() (do note that drivers needs to update the
 device last busy mark, pm_runtime_mark_last_busy(), to control the delay under
 this circumstance).  To prevent this (for example, if the callback routine has
 started a delayed suspend), the routine must return a non-zero value.  Negative
@@ -409,6 +409,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
       pm_request_idle(dev) and return its result
 
   `int pm_runtime_put_autosuspend(struct device *dev);`
+    - does the same as __pm_runtime_put_autosuspend() for now, but in the
+      future, will also call pm_runtime_mark_last_busy() as well, DO NOT USE!
+
+  `int __pm_runtime_put_autosuspend(struct device *dev);`
     - decrement the device's usage counter; if the result is 0 then run
       pm_request_autosuspend(dev) and return its result
 
@@ -539,6 +543,7 @@ It is safe to execute the following helper functions from interrupt context:
 - pm_runtime_put_noidle()
 - pm_runtime_put()
 - pm_runtime_put_autosuspend()
+- __pm_runtime_put_autosuspend()
 - pm_runtime_enable()
 - pm_suspend_ignore_children()
 - pm_runtime_set_active()
@@ -864,9 +869,9 @@ automatically be delayed until the desired period of inactivity has elapsed.
 
 Inactivity is determined based on the power.last_busy field.  Drivers should
 call pm_runtime_mark_last_busy() to update this field after carrying out I/O,
-typically just before calling pm_runtime_put_autosuspend().  The desired length
-of the inactivity period is a matter of policy.  Subsystems can set this length
-initially by calling pm_runtime_set_autosuspend_delay(), but after device
+typically just before calling __pm_runtime_put_autosuspend().  The desired
+length of the inactivity period is a matter of policy.  Subsystems can set this
+length initially by calling pm_runtime_set_autosuspend_delay(), but after device
 registration the length should be controlled by user space, using the
 /sys/devices/.../power/autosuspend_delay_ms attribute.
 
@@ -877,7 +882,7 @@ instead of the non-autosuspend counterparts::
 
 	Instead of: pm_runtime_suspend    use: pm_runtime_autosuspend;
 	Instead of: pm_schedule_suspend   use: pm_request_autosuspend;
-	Instead of: pm_runtime_put        use: pm_runtime_put_autosuspend;
+	Instead of: pm_runtime_put        use: __pm_runtime_put_autosuspend;
 	Instead of: pm_runtime_put_sync   use: pm_runtime_put_sync_autosuspend.
 
 Drivers may also continue to use the non-autosuspend helper functions; they
@@ -916,7 +921,7 @@ Here is a schematic pseudo-code example::
 		lock(&foo->private_lock);
 		if (--foo->num_pending_requests == 0) {
 			pm_runtime_mark_last_busy(&foo->dev);
-			pm_runtime_put_autosuspend(&foo->dev);
+			__pm_runtime_put_autosuspend(&foo->dev);
 		} else {
 			foo_process_next_request(foo);
 		}

include/linux/pm_runtime.h

@@ -448,6 +448,18 @@ static inline int pm_runtime_put(struct device *dev)
 	return __pm_runtime_idle(dev, RPM_GET_PUT | RPM_ASYNC);
 }
 
+/**
+ * __pm_runtime_put_autosuspend - Drop device usage counter and queue autosuspend if 0.
+ * @dev: Target device.
+ *
+ * Decrement the runtime PM usage counter of @dev and if it turns out to be
+ * equal to 0, queue up a work item for @dev like in pm_request_autosuspend().
+ */
+static inline int __pm_runtime_put_autosuspend(struct device *dev)
+{
+	return __pm_runtime_suspend(dev, RPM_GET_PUT | RPM_ASYNC | RPM_AUTO);
+}
+
 /**
  * pm_runtime_put_autosuspend - Drop device usage counter and queue autosuspend if 0.
  * @dev: Target device.