linux-kernel - [PATCH v1] PM: sleep: core: Synchronize runtime PM status of parents and children

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Message-ID: <12619233.O9o76ZdvQC@rjwysocki.net>
Date: Tue, 28 Jan 2025 20:24:41 +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>, Bjorn Helgaas <helgaas@...nel.org>,
 Linux PCI <linux-pci@...r.kernel.org>, Ulf Hansson <ulf.hansson@...aro.org>,
 Johan Hovold <johan@...nel.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Kevin Xie <kevin.xie@...rfivetech.com>
Subject:
 [PATCH v1] PM: sleep: core: Synchronize runtime PM status of parents and
 children

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

Commit 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the
resume phase") overlooked the case in which the parent of a device with
DPM_FLAG_SMART_SUSPEND set did not use that flag and could be runtime-
suspended before a transition into a system-wide sleep state.  In that
case, if the child is resumed during the subsequent transition from
that state into the working state, its runtime PM status will be set to
RPM_ACTIVE, but the runtime PM status of the parent will not be updated
accordingly, even though the parent will be resumed too, because of the
dev_pm_skip_suspend() check in device_resume_noirq().

Address this problem by tracking the need to set the runtime PM status
to RPM_ACTIVE during system-wide resume transitions for devices with
DPM_FLAG_SMART_SUSPEND set and all of the devices depended on by them.

Fixes: 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase")
Closes: https://lore.kernel.org/linux-pm/Z30p2Etwf3F2AUvD@hovoldconsulting.com/
Reported-by: Johan Hovold <johan@...nel.org>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/base/power/main.c |   29 ++++++++++++++++++++---------
 include/linux/pm.h        |    1 +
 2 files changed, 21 insertions(+), 9 deletions(-)

--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -656,13 +656,15 @@
 	 * so change its status accordingly.
 	 *
 	 * Otherwise, the device is going to be resumed, so set its PM-runtime
-	 * status to "active", but do that only if DPM_FLAG_SMART_SUSPEND is set
-	 * to avoid confusing drivers that don't use it.
+	 * status to "active" unless its power.set_active flag is clear, in
+	 * which case it is not necessary to update its PM-runtime status.
 	 */
-	if (skip_resume)
+	if (skip_resume) {
 		pm_runtime_set_suspended(dev);
-	else if (dev_pm_skip_suspend(dev))
+	} else if (dev->power.set_active) {
 		pm_runtime_set_active(dev);
+		dev->power.set_active = false;
+	}

 	if (dev->pm_domain) {
 		info = "noirq power domain ";
@@ -1189,18 +1191,24 @@
 	return PMSG_ON;
 }

-static void dpm_superior_set_must_resume(struct device *dev)
+static void dpm_superior_set_must_resume(struct device *dev, bool set_active)
 {
 	struct device_link *link;
 	int idx;

-	if (dev->parent)
+	if (dev->parent) {
 		dev->parent->power.must_resume = true;
+		if (set_active)
+			dev->parent->power.set_active = true;
+	}

 	idx = device_links_read_lock();

-	list_for_each_entry_rcu_locked(link, &dev->links.suppliers, c_node)
+	list_for_each_entry_rcu_locked(link, &dev->links.suppliers, c_node) {
 		link->supplier->power.must_resume = true;
+		if (set_active)
+			link->supplier->power.set_active = true;
+	}

 	device_links_read_unlock(idx);
 }
@@ -1278,8 +1286,11 @@
 	      dev->power.may_skip_resume))
 		dev->power.must_resume = true;

-	if (dev->power.must_resume)
-		dpm_superior_set_must_resume(dev);
+	if (dev->power.must_resume) {
+		dev->power.set_active = dev->power.set_active ||
+			dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND);
+		dpm_superior_set_must_resume(dev, dev->power.set_active);
+	}

 Complete:
 	complete_all(&dev->power.completion);
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -683,6 +683,7 @@
 	bool			no_pm_callbacks:1;	/* Owned by the PM core */
 	bool			async_in_progress:1;	/* Owned by the PM core */
 	bool			must_resume:1;		/* Owned by the PM core */
+	bool			set_active:1;		/* Owned by the PM core */
 	bool			may_skip_resume:1;	/* Set by subsystems */
 #else
 	bool			should_wakeup:1;