[PATCH 2/2] pm: runtime: Add pm_runtime_put_autosuspend() replacement

Sakari Ailus
2024-01-09T13:36:48Z

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>
---
Documentation/power/runtime_pm.rst | 17 +++++++++++------
include/linux/pm_runtime.h | 12 ++++++++++++
2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst
index da99379071a4..6fa50e4f87ce 100644
--- a/Documentation/power/runtime_pm.rst
+++ b/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);
}
diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index 13cd526634c1..d28df13ffe4d 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -482,6 +482,18 @@ 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.
--
2.39.2