linux-kernel - [PATCH v2] PM: sleep: Adjust check before setting power.must

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Message-ID: <3353728.44csPzL39Z@rjwysocki.net>
Date: Thu, 27 Feb 2025 11:53:50 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Alan Stern <stern@...land.harvard.edu>, Ulf Hansson <ulf.hansson@...aro.org>,
 Johan Hovold <johan@...nel.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Jon Hunter <jonathanh@...dia.com>
Subject: [PATCH v2] PM: sleep: Adjust check before setting power.must_resume

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

The check before setting power.must_resume in device_suspend_noirq()
does not take power.child_count into account, but it should do that, so
use pm_runtime_need_not_resume() in it for this purpose and adjust the
comment next to it accordingly.

Fixes: 107d47b2b95e ("PM: sleep: core: Simplify the SMART_SUSPEND flag handling")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

The previous version of this patch is here:

https://lore.kernel.org/linux-pm/3548152.QJadu78ljV@rjwysocki.net/

v1 -> v2:
   * Changelog rewrite.
   * Added the Fixes: tag.
   * Refined the comment adjustment.

---
 drivers/base/power/main.c    |   13 ++++++-------
 drivers/base/power/runtime.c |    2 +-
 include/linux/pm_runtime.h   |    2 ++
 3 files changed, 9 insertions(+), 8 deletions(-)

--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1382,14 +1382,13 @@
 	dev->power.is_noirq_suspended = true;
 
 	/*
-	 * Skipping the resume of devices that were in use right before the
-	 * system suspend (as indicated by their PM-runtime usage counters)
-	 * would be suboptimal.  Also resume them if doing that is not allowed
-	 * to be skipped.
+	 * Devices must be resumed unless they are explicitly allowed to be left
+	 * in suspend, but even in that case skipping the resume of devices that
+	 * were in use right before the system suspend (as indicated by their
+	 * runtime PM usage counters and child counters) would be suboptimal.
 	 */
-	if (atomic_read(&dev->power.usage_count) > 1 ||
-	    !(dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME) &&
-	      dev->power.may_skip_resume))
+	if (!(dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME) &&
+	      dev->power.may_skip_resume) || !pm_runtime_need_not_resume(dev))
 		dev->power.must_resume = true;
 
 	if (dev->power.must_resume)
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -1897,7 +1897,7 @@
 	pm_request_idle(link->supplier);
 }
 
-static bool pm_runtime_need_not_resume(struct device *dev)
+bool pm_runtime_need_not_resume(struct device *dev)
 {
 	return atomic_read(&dev->power.usage_count) <= 1 &&
 		(atomic_read(&dev->power.child_count) == 0 ||
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -66,6 +66,7 @@
 
 extern int pm_generic_runtime_suspend(struct device *dev);
 extern int pm_generic_runtime_resume(struct device *dev);
+extern bool pm_runtime_need_not_resume(struct device *dev);
 extern int pm_runtime_force_suspend(struct device *dev);
 extern int pm_runtime_force_resume(struct device *dev);
 
@@ -254,6 +255,7 @@
 
 static inline int pm_generic_runtime_suspend(struct device *dev) { return 0; }
 static inline int pm_generic_runtime_resume(struct device *dev) { return 0; }
+static inline bool pm_runtime_need_not_resume(struct device *dev) {return true; }
 static inline int pm_runtime_force_suspend(struct device *dev) { return 0; }
 static inline int pm_runtime_force_resume(struct device *dev) { return 0; }