[PATCH v3 4/5] PM: sleep: Make async suspend handle suppliers like parents

From: Rafael J. Wysocki
Date: Fri Mar 14 2025 - 09:19:33 EST


From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Following previous changes, avoid starting "async" suspend processing
upfront for devices that have consumers and start "async" suspend
processing for the supplies of a device after suspending the device
itself.

Suggested-by: Saravana Kannan <saravanak@xxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---

New patch in v3.

---
drivers/base/power/main.c | 37 +++++++++++++++++++++++++++++++------
1 file changed, 31 insertions(+), 6 deletions(-)

--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1249,10 +1249,15 @@
return false;
}

- return true;
+ /*
+ * Since this function is required to run under dpm_list_mtx, the
+ * list_empty() below will only return true if the device's list of
+ * consumers is actually empty before calling it.
+ */
+ return list_empty(&dev->links.consumers);
}

-static void dpm_async_suspend_parent(struct device *dev, async_func_t func)
+static bool dpm_async_suspend_parent(struct device *dev, async_func_t func)
{
guard(mutex)(&dpm_list_mtx);

@@ -1264,11 +1269,31 @@
* deleted before it.
*/
if (!device_pm_initialized(dev))
- return;
+ return false;

/* Start processing the device's parent if it is "async". */
if (dev->parent)
dpm_async_with_cleanup(dev->parent, func);
+
+ return true;
+}
+
+static void dpm_async_suspend_superior(struct device *dev, async_func_t func)
+{
+ struct device_link *link;
+ int idx;
+
+ if (!dpm_async_suspend_parent(dev, func))
+ return;
+
+ idx = device_links_read_lock();
+
+ /* Start processing the device's "async" suppliers. */
+ list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
+ if (READ_ONCE(link->status) != DL_STATE_DORMANT)
+ dpm_async_with_cleanup(link->supplier, func);
+
+ device_links_read_unlock(idx);
}

/**
@@ -1392,7 +1417,7 @@
if (error || async_error)
return error;

- dpm_async_suspend_parent(dev, async_suspend_noirq);
+ dpm_async_suspend_superior(dev, async_suspend_noirq);

return 0;
}
@@ -1588,7 +1613,7 @@
if (error || async_error)
return error;

- dpm_async_suspend_parent(dev, async_suspend_late);
+ dpm_async_suspend_superior(dev, async_suspend_late);

return 0;
}
@@ -1879,7 +1904,7 @@
if (error || async_error)
return error;

- dpm_async_suspend_parent(dev, async_suspend);
+ dpm_async_suspend_superior(dev, async_suspend);

return 0;
}