FAILED: patch "[PATCH] pmdomain: core: Fix detach procedure for virtual devices in" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 26735dfdd8930d9ef1fa92e590a9bf77726efdf6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051202-enjoyably-emcee-b24b@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 26735dfdd8930d9ef1fa92e590a9bf77726efdf6 Mon Sep 17 00:00:00 2001
From: Ulf Hansson <[email protected]>
Date: Fri, 17 Apr 2026 13:13:31 +0200
Subject: [PATCH] pmdomain: core: Fix detach procedure for virtual devices in
genpd

If a device is attached to a PM domain through genpd_dev_pm_attach_by_id(), genpd calls pm_runtime_enable() for the corresponding virtual device that it registers. While this avoids boilerplate code in drivers, there is no corresponding call to pm_runtime_disable() in genpd_dev_pm_detach().

This means these virtual devices are typically detached from its genpd, while runtime PM remains enabled for them, which is not how things are designed to work. In worst cases it may lead to critical errors, like a NULL pointer dereference bug in genpd_runtime_suspend(), which was recently reported. For another case, we may end up keeping an unnecessary vote for a performance state for the device.

To fix these problems, let's add this missing call to pm_runtime_disable() in genpd_dev_pm_detach().

index 4d32fc676aaf..71e930e80178 100644
@@ -3089,6 +3089,7 @@ static const struct bus_type genpd_bus_type = {
 static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 {
 	struct generic_pm_domain *pd;
+	bool is_virt_dev;
 	unsigned int i;
 	int ret = 0;
 

@@ -3098,6 +3099,13 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 
 	dev_dbg(dev, "removing from PM domain %s\n", pd->name);
 
+	/* Check if the device was created by genpd at attach. */
+	is_virt_dev = dev->bus == &genpd_bus_type;
+
+	/* Disable runtime PM if we enabled it at attach. */
+	if (is_virt_dev)
+		pm_runtime_disable(dev);
+
 	/* Drop the default performance state */
 	if (dev_gpd_data(dev)->default_pstate) {
 		dev_pm_genpd_set_performance_state(dev, 0);

@@ -3123,7 +3131,7 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 	genpd_queue_power_off_work(pd);
 
 	/* Unregister the device if it was created by genpd. */
-	if (dev->bus == &genpd_bus_type)
+	if (is_virt_dev)
 		device_unregister(dev);
 }
 

From: Ulf Hansson <[email protected]>

[ Upstream commit 26735dfdd8930d9ef1fa92e590a9bf77726efdf6 ]

If a device is attached to a PM domain through genpd_dev_pm_attach_by_id(), genpd calls pm_runtime_enable() for the corresponding virtual device that it registers. While this avoids boilerplate code in drivers, there is no corresponding call to pm_runtime_disable() in genpd_dev_pm_detach().

This means these virtual devices are typically detached from its genpd, while runtime PM remains enabled for them, which is not how things are designed to work. In worst cases it may lead to critical errors, like a NULL pointer dereference bug in genpd_runtime_suspend(), which was recently reported. For another case, we may end up keeping an unnecessary vote for a performance state for the device.

To fix these problems, let's add this missing call to pm_runtime_disable() in genpd_dev_pm_detach().

---
 drivers/base/power/domain.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

index d1dae47f3534b..5bee0a8975003 100644
@@ -2676,6 +2676,7 @@ static struct bus_type genpd_bus_type = {
 static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 {
 	struct generic_pm_domain *pd;
+	bool is_virt_dev;
 	unsigned int i;
 	int ret = 0;
 

@@ -2685,6 +2686,13 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 
 	dev_dbg(dev, "removing from PM domain %s\n", pd->name);
 
+	/* Check if the device was created by genpd at attach. */
+	is_virt_dev = dev->bus == &genpd_bus_type;
+
+	/* Disable runtime PM if we enabled it at attach. */
+	if (is_virt_dev)
+		pm_runtime_disable(dev);
+
 	/* Drop the default performance state */
 	if (dev_gpd_data(dev)->default_pstate) {
 		dev_pm_genpd_set_performance_state(dev, 0);

@@ -2710,7 +2718,7 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
 	genpd_queue_power_off_work(pd);
 
 	/* Unregister the device if it was created by genpd. */
-	if (dev->bus == &genpd_bus_type)
+	if (is_virt_dev)
 		device_unregister(dev);
 }
 

2.53.0