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[PATCH] PCI: of: Skip dynamic nodes for bridges without a subordinate bus

Angel J posted 1 patch 1 week, 6 days ago 
drivers/pci/of.c | 4 ++++
1 file changed, 4 insertions(+)
[PATCH] PCI: of: Skip dynamic nodes for bridges without a subordinate bus
Posted by Angel J 1 week, 6 days ago 
A device can satisfy pci_is_bridge() without having a subordinate bus.
The dynamic OF helpers for bus-range and interrupt-map dereference
pdev->subordinate without checking it.

On a Dell XPS 8940, device 0000:00:00.0 [8086:4c43] has no subordinate
bus, and enabling CONFIG_PCI_DYNAMIC_OF_NODES causes an early boot hang.

Skip dynamic OF node creation for bridges without a subordinate bus.
This allows the machine to boot while preserving node creation for the
other bridges.

Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
Cc: stable@vger.kernel.org
Signed-off-by: Angel J <iamanaws@httpd.dev>
---
 drivers/pci/of.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index a51dff91b..971c79c2a 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -765,6 +765,10 @@ void of_pci_make_dev_node(struct pci_dev *pdev)
 	if (!ppnode)
 		return;
 
+	/* Bridge properties require a subordinate bus. */
+	if (pci_is_bridge(pdev) && !pdev->subordinate)
+		return;
+
 	if (pci_is_bridge(pdev))
 		pci_type = "pci";
 	else
-- 
2.54.0
[PATCH v2] PCI: of_property: Omit bus properties without a subordinate bus
Posted by Angel J 1 week, 6 days ago 
A device can satisfy pci_is_bridge() without having a subordinate bus.
The dynamic OF helpers for bus-range and interrupt-map dereference
pdev->subordinate without checking it.

On a Dell XPS 8940, device 0000:00:00.0 [8086:4c43] has no subordinate
bus, and enabling CONFIG_PCI_DYNAMIC_OF_NODES causes an early boot hang.

Generate bus-range and interrupt-map only when a subordinate bus exists.
Keep the node and its remaining properties for bridges without one.

Boot-tested on Linux 6.18.44 with CONFIG_PCI_DYNAMIC_OF_NODES=y. The
system boots and the node for 00:00.0 retains device_type, reg and
compatible. The other bridges retain their nodes and bus ranges.

Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
Cc: stable@vger.kernel.org
Signed-off-by: Angel J <iamanaws@httpd.dev>
---
Changes in v2:
- Keep the dynamic OF node and skip only bus-range and interrupt-map
  when no subordinate bus exists, following review of v1.
- Tested on Linux 6.18.44 with the v1 guard removed.

 drivers/pci/of_property.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
index 75a358f73..acd2e0f70 100644
--- a/drivers/pci/of_property.c
+++ b/drivers/pci/of_property.c
@@ -361,13 +361,15 @@ int of_pci_add_properties(struct pci_dev *pdev, struct of_changeset *ocs,
 		if (ret)
 			return ret;
 
-		ret = of_pci_prop_bus_range(pdev, ocs, np);
-		if (ret)
-			return ret;
+		if (pdev->subordinate) {
+			ret = of_pci_prop_bus_range(pdev, ocs, np);
+			if (ret)
+				return ret;
 
-		ret = of_pci_prop_intr_map(pdev, ocs, np);
-		if (ret)
-			return ret;
+			ret = of_pci_prop_intr_map(pdev, ocs, np);
+			if (ret)
+				return ret;
+		}
 	} else {
 		ret = of_pci_prop_intr_ctrl(pdev, ocs, np);
 		if (ret)
-- 
2.54.0
Re: [PATCH v2] PCI: of_property: Omit bus properties without a subordinate bus
Posted by Bjorn Helgaas 1 week, 1 day ago 
On Fri, Sep 11, 2026 at 09:31:06PM -0700, Angel J wrote:
> A device can satisfy pci_is_bridge() without having a subordinate bus.
> The dynamic OF helpers for bus-range and interrupt-map dereference
> pdev->subordinate without checking it.
> 
> On a Dell XPS 8940, device 0000:00:00.0 [8086:4c43] has no subordinate
> bus, and enabling CONFIG_PCI_DYNAMIC_OF_NODES causes an early boot hang.
> 
> Generate bus-range and interrupt-map only when a subordinate bus exists.
> Keep the node and its remaining properties for bridges without one.
> 
> Boot-tested on Linux 6.18.44 with CONFIG_PCI_DYNAMIC_OF_NODES=y. The
> system boots and the node for 00:00.0 retains device_type, reg and
> compatible. The other bridges retain their nodes and bus ranges.

I think this is the right approach, with something like this included
in the commit log:

  A bridge (a device with a Type 1 header) may not have a secondary
  bus allocated (pdev->subordinate), e.g., if there are no available
  bus numbers or the bridge secondary/subordinate bus numbers are not
  writable.

I don't think it's necessary to connect this with [8086:4c43] because
I think this situation is very common, and I don't want to leave the
impression that it's related to a Dell system or to that specific
device.  It's just a bug to assume that pci_is_bridge() implies
pdev->subordinate is valid.

> Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
> Cc: stable@vger.kernel.org
> Signed-off-by: Angel J <iamanaws@httpd.dev>
> ---
> Changes in v2:
> - Keep the dynamic OF node and skip only bus-range and interrupt-map
>   when no subordinate bus exists, following review of v1.
> - Tested on Linux 6.18.44 with the v1 guard removed.
> 
>  drivers/pci/of_property.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
> index 75a358f73..acd2e0f70 100644
> --- a/drivers/pci/of_property.c
> +++ b/drivers/pci/of_property.c
> @@ -361,13 +361,15 @@ int of_pci_add_properties(struct pci_dev *pdev, struct of_changeset *ocs,
>  		if (ret)
>  			return ret;
>  
> -		ret = of_pci_prop_bus_range(pdev, ocs, np);
> -		if (ret)
> -			return ret;
> +		if (pdev->subordinate) {
> +			ret = of_pci_prop_bus_range(pdev, ocs, np);
> +			if (ret)
> +				return ret;
>  
> -		ret = of_pci_prop_intr_map(pdev, ocs, np);
> -		if (ret)
> -			return ret;
> +			ret = of_pci_prop_intr_map(pdev, ocs, np);
> +			if (ret)
> +				return ret;

I think this is the best solution, but I do think it would be a little
cleaner to check for pdev->subordinate inside of_pci_prop_bus_range()
and of_pci_prop_intr_map() instead of assuming things here about the
internals of those functions.  We could just make them return
immediately without doing anything.

> +		}
>  	} else {
>  		ret = of_pci_prop_intr_ctrl(pdev, ocs, np);
>  		if (ret)
> -- 
> 2.54.0
>
[PATCH v3] PCI: of_property: Omit bus properties without a subordinate bus
Posted by Bjorn Helgaas 6 days, 16 hours ago 
Author: Angel J <iamanaws@httpd.dev>

PCI: of_property: Omit bus properties without a subordinate bus

A bridge (a device with a Type 1 header) may not have a secondary bus
allocated (pdev->subordinate), e.g., if there are no available bus numbers
or the bridge secondary/subordinate bus numbers are not writable.

The dynamic OF helpers of_pci_prop_bus_range() and of_pci_prop_intr_map()
dereference pdev->subordinate without checking it.  When
CONFIG_PCI_DYNAMIC_OF_NODES is enabled, this can cause a NULL pointer
dereference and early boot hang.

Generate 'bus-range' and 'interrupt-map' properties only when a subordinate
bus exists.  Keep the node and its remaining properties for bridges without
one.

The problem was latent since 407d1a51921e ("PCI: Create device tree node
for bridge"), but wasn't reachable until 1f340724419e ("PCI: of: Create
device tree PCI host bridge node"), which appeared in v6.15.  Before
1f340724419e, of_pci_make_dev_node() returned early because the parent OF
node was missing.

Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
Signed-off-by: Angel J <iamanaws@httpd.dev>
[bhelgaas: move pdev->subordinate test to callees, commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org	# v6.6+
Link: https://patch.msgid.link/20260912043106.10715-1-iamanaws@httpd.dev
---
Changes in v3:
- Move pdev->subordinate tests to of_pci_prop_bus_range() and
  of_pci_prop_intr_map()

Changes in v2
(https://lore.kernel.org/all/20260912043106.10715-1-iamanaws@httpd.dev):
- Keep the dynamic OF node and skip only bus-range and interrupt-map
  when no subordinate bus exists, following review of v1.
- Tested on Linux 6.18.44 with the v1 guard removed.

v1
(https://lore.kernel.org/all/20260911230420.26244-1-iamanaws@httpd.dev)

diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
index 75a358f73e69..1500740cc55d 100644
--- a/drivers/pci/of_property.c
+++ b/drivers/pci/of_property.c
@@ -95,9 +95,13 @@ static int of_pci_prop_bus_range(struct pci_dev *pdev,
 				 struct of_changeset *ocs,
 				 struct device_node *np)
 {
-	u32 bus_range[] = { pdev->subordinate->busn_res.start,
-			    pdev->subordinate->busn_res.end };
+	u32 bus_range[2];
 
+	if (!pdev->subordinate)
+		return 0;
+
+	bus_range[0] = pdev->subordinate->busn_res.start;
+	bus_range[1] = pdev->subordinate->busn_res.end;
 	return of_changeset_add_prop_u32_array(ocs, np, "bus-range", bus_range,
 					       ARRAY_SIZE(bus_range));
 }
@@ -220,6 +224,9 @@ static int of_pci_prop_intr_map(struct pci_dev *pdev, struct of_changeset *ocs,
 	int ret;
 	u8 pin;
 
+	if (!pdev->subordinate)
+		return 0;
+
 	pnode = pci_device_to_OF_node(pdev->bus->self);
 	if (!pnode)
 		pnode = pci_bus_to_OF_node(pdev->bus);
Re: [PATCH v3] PCI: of_property: Omit bus properties without a subordinate bus
Posted by Bjorn Helgaas 6 days, 16 hours ago 
On Fri, Sep 18, 2026 at 02:55:40PM -0500, Bjorn Helgaas wrote:
> Author: Angel J <iamanaws@httpd.dev>
> 
> PCI: of_property: Omit bus properties without a subordinate bus
> 
> A bridge (a device with a Type 1 header) may not have a secondary bus
> allocated (pdev->subordinate), e.g., if there are no available bus numbers
> or the bridge secondary/subordinate bus numbers are not writable.
> 
> The dynamic OF helpers of_pci_prop_bus_range() and of_pci_prop_intr_map()
> dereference pdev->subordinate without checking it.  When
> CONFIG_PCI_DYNAMIC_OF_NODES is enabled, this can cause a NULL pointer
> dereference and early boot hang.
> 
> Generate 'bus-range' and 'interrupt-map' properties only when a subordinate
> bus exists.  Keep the node and its remaining properties for bridges without
> one.
> 
> The problem was latent since 407d1a51921e ("PCI: Create device tree node
> for bridge"), but wasn't reachable until 1f340724419e ("PCI: of: Create
> device tree PCI host bridge node"), which appeared in v6.15.  Before
> 1f340724419e, of_pci_make_dev_node() returned early because the parent OF
> node was missing.
> 
> Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
> Signed-off-by: Angel J <iamanaws@httpd.dev>
> [bhelgaas: move pdev->subordinate test to callees, commit log]
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> Cc: stable@vger.kernel.org	# v6.6+
> Link: https://patch.msgid.link/20260912043106.10715-1-iamanaws@httpd.dev

I put this on pci/for-linus, planning to be in v7.3, but I would love
to have testing reports to make sure it still works as the v2 does.

> ---
> Changes in v3:
> - Move pdev->subordinate tests to of_pci_prop_bus_range() and
>   of_pci_prop_intr_map()
> 
> Changes in v2
> (https://lore.kernel.org/all/20260912043106.10715-1-iamanaws@httpd.dev):
> - Keep the dynamic OF node and skip only bus-range and interrupt-map
>   when no subordinate bus exists, following review of v1.
> - Tested on Linux 6.18.44 with the v1 guard removed.
> 
> v1
> (https://lore.kernel.org/all/20260911230420.26244-1-iamanaws@httpd.dev)
> 
> diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
> index 75a358f73e69..1500740cc55d 100644
> --- a/drivers/pci/of_property.c
> +++ b/drivers/pci/of_property.c
> @@ -95,9 +95,13 @@ static int of_pci_prop_bus_range(struct pci_dev *pdev,
>  				 struct of_changeset *ocs,
>  				 struct device_node *np)
>  {
> -	u32 bus_range[] = { pdev->subordinate->busn_res.start,
> -			    pdev->subordinate->busn_res.end };
> +	u32 bus_range[2];
>  
> +	if (!pdev->subordinate)
> +		return 0;
> +
> +	bus_range[0] = pdev->subordinate->busn_res.start;
> +	bus_range[1] = pdev->subordinate->busn_res.end;
>  	return of_changeset_add_prop_u32_array(ocs, np, "bus-range", bus_range,
>  					       ARRAY_SIZE(bus_range));
>  }
> @@ -220,6 +224,9 @@ static int of_pci_prop_intr_map(struct pci_dev *pdev, struct of_changeset *ocs,
>  	int ret;
>  	u8 pin;
>  
> +	if (!pdev->subordinate)
> +		return 0;
> +
>  	pnode = pci_device_to_OF_node(pdev->bus->self);
>  	if (!pnode)
>  		pnode = pci_bus_to_OF_node(pdev->bus);
Re: [PATCH v3] PCI: of_property: Omit bus properties without a subordinate bus
Posted by Angel J 6 days, 16 hours ago 
I didn't reply cuz I'm out for 3 weeks without access to that machine, so I can't test or confirm it works as expected (even though probably does)

Still, I will try to confirm as soon as I can.

Thanks

On Friday, September 18th, 2026 at 13:20, Bjorn Helgaas <helgaas@kernel.org> wrote:

> On Fri, Sep 18, 2026 at 02:55:40PM -0500, Bjorn Helgaas wrote:
> > Author: Angel J <iamanaws@httpd.dev>
> >
> > PCI: of_property: Omit bus properties without a subordinate bus
> >
> > A bridge (a device with a Type 1 header) may not have a secondary bus
> > allocated (pdev->subordinate), e.g., if there are no available bus numbers
> > or the bridge secondary/subordinate bus numbers are not writable.
> >
> > The dynamic OF helpers of_pci_prop_bus_range() and of_pci_prop_intr_map()
> > dereference pdev->subordinate without checking it.  When
> > CONFIG_PCI_DYNAMIC_OF_NODES is enabled, this can cause a NULL pointer
> > dereference and early boot hang.
> >
> > Generate 'bus-range' and 'interrupt-map' properties only when a subordinate
> > bus exists.  Keep the node and its remaining properties for bridges without
> > one.
> >
> > The problem was latent since 407d1a51921e ("PCI: Create device tree node
> > for bridge"), but wasn't reachable until 1f340724419e ("PCI: of: Create
> > device tree PCI host bridge node"), which appeared in v6.15.  Before
> > 1f340724419e, of_pci_make_dev_node() returned early because the parent OF
> > node was missing.
> >
> > Fixes: 407d1a51921e ("PCI: Create device tree node for bridge")
> > Signed-off-by: Angel J <iamanaws@httpd.dev>
> > [bhelgaas: move pdev->subordinate test to callees, commit log]
> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: stable@vger.kernel.org	# v6.6+
> > Link: https://patch.msgid.link/20260912043106.10715-1-iamanaws@httpd.dev
> 

> I put this on pci/for-linus, planning to be in v7.3, but I would love
> to have testing reports to make sure it still works as the v2 does.
> 

> > ---
> > Changes in v3:
> > - Move pdev->subordinate tests to of_pci_prop_bus_range() and
> >   of_pci_prop_intr_map()
> >
> > Changes in v2
> > (https://lore.kernel.org/all/20260912043106.10715-1-iamanaws@httpd.dev):
> > - Keep the dynamic OF node and skip only bus-range and interrupt-map
> >   when no subordinate bus exists, following review of v1.
> > - Tested on Linux 6.18.44 with the v1 guard removed.
> >
> > v1
> > (https://lore.kernel.org/all/20260911230420.26244-1-iamanaws@httpd.dev)
> >
> > diff --git a/drivers/pci/of_property.c b/drivers/pci/of_property.c
> > index 75a358f73e69..1500740cc55d 100644
> > --- a/drivers/pci/of_property.c
> > +++ b/drivers/pci/of_property.c
> > @@ -95,9 +95,13 @@ static int of_pci_prop_bus_range(struct pci_dev *pdev,
> >  				 struct of_changeset *ocs,
> >  				 struct device_node *np)
> >  {
> > -	u32 bus_range[] = { pdev->subordinate->busn_res.start,
> > -			    pdev->subordinate->busn_res.end };
> > +	u32 bus_range[2];
> >
> > +	if (!pdev->subordinate)
> > +		return 0;
> > +
> > +	bus_range[0] = pdev->subordinate->busn_res.start;
> > +	bus_range[1] = pdev->subordinate->busn_res.end;
> >  	return of_changeset_add_prop_u32_array(ocs, np, "bus-range", bus_range,
> >  					       ARRAY_SIZE(bus_range));
> >  }
> > @@ -220,6 +224,9 @@ static int of_pci_prop_intr_map(struct pci_dev *pdev, struct of_changeset *ocs,
> >  	int ret;
> >  	u8 pin;
> >
> > +	if (!pdev->subordinate)
> > +		return 0;
> > +
> >  	pnode = pci_device_to_OF_node(pdev->bus->self);
> >  	if (!pnode)
> >  		pnode = pci_bus_to_OF_node(pdev->bus);
>

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