PM: runtime: Update kerneldoc return codes

APIs based on __pm_runtime_idle() (pm_runtime_idle(), pm_request_idle())
do not return 1 when already suspended. They return -EAGAIN. This is
already covered in the docs, so the entry for "1" is redundant and
conflicting.

(pm_runtime_put() and pm_runtime_put_sync() were previously incorrect,
but that's fixed in "PM: runtime: pm_runtime_put{,_sync}() returns 1
when already suspended", to ensure consistency with APIs like
pm_runtime_put_autosuspend().)

RPM_GET_PUT APIs based on __pm_runtime_suspend() do return 1 when
already suspended, but the language is a little unclear -- it's not
really an "error", so it seems better to list as a clarification before
the 0/success case. Additionally, they only actually return 1 when the
refcount makes it to 0; if the usage counter is still non-zero, we
return 0.

pm_runtime_put(), etc., also don't appear at first like they can ever
see "-EAGAIN: Runtime PM usage_count non-zero", because in non-racy
conditions, pm_runtime_put() would drop its reference count, see it's
non-zero, and return early (in __pm_runtime_idle()). However, it's
possible to race with another actor that increments the usage_count
afterward, since rpm_idle() is protected by a separate lock; in such a
case, we may see -EAGAIN.

Because this case is only seen in the presence of concurrent actors, it
makes sense to clarify that this is when "usage_count **became**
non-zero", by way of some racing actor.

Lastly, pm_runtime_put_sync_suspend() duplicated some -EAGAIN language.
Fix that.

Fixes: 271ff96 ("PM: runtime: Document return values of suspend-related API functions")
Link: https://lore.kernel.org/linux-pm/aJ5pkEJuixTaybV4@google.com/
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: 6.17+ <stable@vger.kernel.org> # 6.17+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: computersforpeace

include/linux/pm_runtime.h

@@ -350,13 +350,12 @@ static inline int pm_runtime_force_resume(struct device *dev) { return -ENXIO; }
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero, Runtime PM status change ongoing
- *            or device not in %RPM_ACTIVE state.
+ * * -EAGAIN: Runtime PM usage counter non-zero, Runtime PM status change
+ *            ongoing or device not in %RPM_ACTIVE state.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  * Other values and conditions for the above values are possible as returned by
  * Runtime PM idle and suspend callbacks.
  */
@@ -370,14 +369,15 @@ static inline int pm_runtime_idle(struct device *dev)
  * @dev: Target device.
  *
  * Return:
+ * * 1: Success; device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter non-zero or Runtime PM status change
+ *            ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  * Other values and conditions for the above values are possible as returned by
  * Runtime PM suspend callbacks.
  */
@@ -396,14 +396,15 @@ static inline int pm_runtime_suspend(struct device *dev)
  * engaging its "idle check" callback.
  *
  * Return:
+ * * 1: Success; device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter non-zero or Runtime PM status change
+ *            ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  * Other values and conditions for the above values are possible as returned by
  * Runtime PM suspend callbacks.
  */
@@ -433,13 +434,12 @@ static inline int pm_runtime_resume(struct device *dev)
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero, Runtime PM status change ongoing
- *            or device not in %RPM_ACTIVE state.
+ * * -EAGAIN: Runtime PM usage counter non-zero, Runtime PM status change
+ *            ongoing or device not in %RPM_ACTIVE state.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  */
 static inline int pm_request_idle(struct device *dev)
 {
@@ -464,15 +464,16 @@ static inline int pm_request_resume(struct device *dev)
  * equivalent pm_runtime_autosuspend() for @dev asynchronously.
  *
  * Return:
+ * * 1: Success; device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter non-zero or Runtime PM status change
+ *            ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  */
 static inline int pm_request_autosuspend(struct device *dev)
 {
@@ -540,15 +541,16 @@ static inline int pm_runtime_resume_and_get(struct device *dev)
  * equal to 0, queue up a work item for @dev like in pm_request_idle().
  *
  * Return:
+ * * 1: Success. Usage counter dropped to zero, but device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter became non-zero or Runtime PM status
+ *            change ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  */
 static inline int pm_runtime_put(struct device *dev)
 {
@@ -565,15 +567,16 @@ DEFINE_FREE(pm_runtime_put, struct device *, if (_T) pm_runtime_put(_T))
  * equal to 0, queue up a work item for @dev like in pm_request_autosuspend().
  *
  * Return:
+ * * 1: Success. Usage counter dropped to zero, but device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter became non-zero or Runtime PM status
+ *            change ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  */
 static inline int __pm_runtime_put_autosuspend(struct device *dev)
 {
@@ -590,15 +593,16 @@ static inline int __pm_runtime_put_autosuspend(struct device *dev)
  * in pm_request_autosuspend().
  *
  * Return:
+ * * 1: Success. Usage counter dropped to zero, but device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter became non-zero or Runtime PM status
+ *            change ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  */
 static inline int pm_runtime_put_autosuspend(struct device *dev)
 {
@@ -619,14 +623,15 @@ static inline int pm_runtime_put_autosuspend(struct device *dev)
  * if it returns an error code.
  *
  * Return:
+ * * 1: Success. Usage counter dropped to zero, but device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter became non-zero or Runtime PM status
+ *            change ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  * Other values and conditions for the above values are possible as returned by
  * Runtime PM suspend callbacks.
  */
@@ -646,15 +651,15 @@ static inline int pm_runtime_put_sync(struct device *dev)
  * if it returns an error code.
  *
  * Return:
+ * * 1: Success. Usage counter dropped to zero, but device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
- * * -EAGAIN: usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter became non-zero or Runtime PM status
+ *            change ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  * Other values and conditions for the above values are possible as returned by
  * Runtime PM suspend callbacks.
  */
@@ -677,15 +682,16 @@ static inline int pm_runtime_put_sync_suspend(struct device *dev)
  * if it returns an error code.
  *
  * Return:
+ * * 1: Success. Usage counter dropped to zero, but device was already suspended.
  * * 0: Success.
  * * -EINVAL: Runtime PM error.
  * * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage counter became non-zero or Runtime PM status
+ *            change ongoing.
  * * -EBUSY: Runtime PM child_count non-zero.
  * * -EPERM: Device PM QoS resume latency 0.
  * * -EINPROGRESS: Suspend already in progress.
  * * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
  * Other values and conditions for the above values are possible as returned by
  * Runtime PM suspend callbacks.
  */