[PATCH v7 0/2] lan966x pci device: Add support for SFPs, simple-bus part

[PATCH v7 0/2] lan966x pci device: Add support for SFPs, simple-bus part

[Herve Codina]

Hi,

Previously, I sent a big picture series adding support for SFP ports
available on the LAN966x PCI device [0].

In this series patches touch several parts and sub-system in the kernel.
Reviews have be done and it makes sense to split the series and send
parts separately.

This current series is the extraction of patches related to the
simple-bus driver. It has to be seen as a continuation of the big
picture series but related to this specific simple-bus part.

Patches 1 and 2 makes the simple-bus driver compatible with fw_devlink
expectation consisting in creating its child devices at probe.

[0] https://lore.kernel.org/all/20260325143555.451852-1-herve.codina@bootlin.com/

Best regards,
Hervé

Changes:

v6 -> v7

  Rebase on top v7.1-rc1

  - Patch 1
    No changes

  - Patch 2
    Fix conflict due to device_has_driver_override() introduction.

Older iterations:
  Patches 4 and 5 in the big picture series
  https://lore.kernel.org/all/20260325143555.451852-1-herve.codina@bootlin.com/

Herve Codina (2):
  bus: simple-pm-bus: Remove child devices when the bus is unbound
  bus: simple-pm-bus: Populate child nodes at probe

 drivers/bus/simple-pm-bus.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

-- 
2.54.0

[PATCH v7 1/2] bus: simple-pm-bus: Remove child devices when the bus is unbound

[Herve Codina]

During its probe, the simple-pm-bus driver (simple-pm-bus compatible
variant) populates its child devices but it doesn't touch them during
its removal.

This leads to bus child devices present and bound to drivers whereas the
bus itself is unbound.

Be consistent and remove child devices when the bus itself is unbound.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/bus/simple-pm-bus.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
index c920bd6fbaaf..4b2a793dfbd9 100644
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -83,6 +83,9 @@ static void simple_pm_bus_remove(struct platform_device *pdev)
 
 	dev_dbg(&pdev->dev, "%s\n", __func__);
 
+	if (pdev->dev.of_node)
+		of_platform_depopulate(&pdev->dev);
+
 	pm_runtime_disable(&pdev->dev);
 }
 
-- 
2.54.0

[PATCH v7 2/2] bus: simple-pm-bus: Populate child nodes at probe

[Herve Codina]

The simple-pm-bus driver handles several simple busses. When it is used
with busses other than a compatible "simple-pm-bus", it doesn't populate
its child devices during its probe.

This confuses fw_devlink and results in wrong or missing devlinks.

Once a driver is bound to a device and the probe() has been called,
device_links_driver_bound() is called.

This function performs operation based on the following assumption:
    If a child firmware node of the bound device is not added as a
    device, it will never be added.

Among operations done on fw_devlinks of those "never be added" devices,
device_links_driver_bound() changes their supplier.

With devices attached to a simple-bus compatible device, this change
leads to wrong devlinks where supplier of devices points to the device
parent (i.e. simple-bus compatible device) instead of the device itself
(i.e. simple-bus child).

When the device attached to the simple-bus is removed, because devlinks
are not correct, its consumers are not removed first.

In order to have correct devlinks created, make the simple-pm-bus driver
compliant with the devlink assumption and create its child devices
during its probe.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/bus/simple-pm-bus.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
index 4b2a793dfbd9..d969bf19a4e9 100644
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -42,14 +42,15 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
 	match = of_match_device(dev->driver->of_match_table, dev);
 	/*
 	 * These are transparent bus devices (not simple-pm-bus matches) that
-	 * have their child nodes populated automatically.  So, don't need to
-	 * do anything more. We only match with the device if this driver is
-	 * the most specific match because we don't want to incorrectly bind to
-	 * a device that has a more specific driver.
+	 * need to have their child nodes populated. So, don't need to do
+	 * anything more except populate child nodes during this probe(). We
+	 * only match with the device if this driver is the most specific match
+	 * because we don't want to incorrectly bind to a device that has a more
+	 * specific driver.
 	 */
 	if (match && match->data) {
 		if (of_property_match_string(np, "compatible", match->compatible) == 0)
-			return 0;
+			goto populate;
 		else
 			return -ENODEV;
 	}
@@ -64,13 +65,14 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(&pdev->dev, bus);
 
-	dev_dbg(&pdev->dev, "%s\n", __func__);
-
 	pm_runtime_enable(&pdev->dev);
 
+populate:
 	if (np)
 		of_platform_populate(np, NULL, lookup, &pdev->dev);
 
+	dev_dbg(&pdev->dev, "%s\n", __func__);
+
 	return 0;
 }
 
@@ -78,7 +80,7 @@ static void simple_pm_bus_remove(struct platform_device *pdev)
 {
 	const void *data = of_device_get_match_data(&pdev->dev);
 
-	if (device_has_driver_override(&pdev->dev) || data)
+	if (device_has_driver_override(&pdev->dev))
 		return;
 
 	dev_dbg(&pdev->dev, "%s\n", __func__);
@@ -86,7 +88,8 @@ static void simple_pm_bus_remove(struct platform_device *pdev)
 	if (pdev->dev.of_node)
 		of_platform_depopulate(&pdev->dev);
 
-	pm_runtime_disable(&pdev->dev);
+	if (!data)
+		pm_runtime_disable(&pdev->dev);
 }
 
 static int simple_pm_bus_runtime_suspend(struct device *dev)
-- 
2.54.0

Re: [PATCH v7 2/2] bus: simple-pm-bus: Populate child nodes at probe

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The patch resolves fw_devlink corruption for transparent buses matched via `of_match_table`, but fails to apply this fix to transparent buses bound via `driver_override`, leaving devlinks broken in that path.
--

commit 428668c33cfe17b55dfc398a9e43567a082e1c3e
Author: Herve Codina <herve.codina@bootlin.com>

bus: simple-pm-bus: Populate child nodes at probe

This commit modifies the simple-pm-bus driver to populate child nodes
during probe for transparent buses matched via of_match_table. This prevents
wrong or missing devlinks when fw_devlink assumes a bound driver will
populate its child firmware nodes.

> diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
> index 4b2a793dfbd90..d969bf19a4e95 100644
> --- a/drivers/bus/simple-pm-bus.c
> +++ b/drivers/bus/simple-pm-bus.c
> @@ -42,14 +42,15 @@ static int simple_pm_bus_probe(struct platform_device *pdev)
>  	match = of_match_device(dev->driver->of_match_table, dev);
>  	/*
>  	 * These are transparent bus devices (not simple-pm-bus matches) that
[ ... ]
>  	if (match && match->data) {
>  		if (of_property_match_string(np, "compatible", match->compatible) == 0)
> -			return 0;
> +			goto populate;
>  		else
>  			return -ENODEV;
>  	}

Does this leave fw_devlink corrupted when the driver is bound using
driver_override?

Looking at simple_pm_bus_probe(), there is an early exit for driver_override
just before this block:

	if (device_has_driver_override(&pdev->dev))
		return 0;

Since it still returns directly instead of jumping to the populate label,
transparent buses bound via the driver_override sysfs attribute will skip
populating their child nodes. This seems to trigger the same wrong
supplier assignments from fw_devlink that this patch intended to fix.

> @@ -78,7 +80,7 @@ static void simple_pm_bus_remove(struct platform_device *pdev)
>  {
>  	const void *data = of_device_get_match_data(&pdev->dev);
>  
> -	if (device_has_driver_override(&pdev->dev) || data)
> +	if (device_has_driver_override(&pdev->dev))
>  		return;
>  
>  	dev_dbg(&pdev->dev, "%s\n", __func__);
> @@ -86,7 +88,8 @@ static void simple_pm_bus_remove(struct platform_device *pdev)
>  	if (pdev->dev.of_node)
>  		of_platform_depopulate(&pdev->dev);

If the driver_override path in probe() is updated to populate children,
should this remove() function also be updated to depopulate them?

Additionally, does checking device_has_driver_override() here risk unbalanced
cleanup? If userspace modifies the driver_override sysfs attribute after
probe() but before remove(), this check could evaluate differently during
removal. Since of_platform_depopulate() safely ignores unpopulated buses,
would it be better to call it unconditionally?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260511155902.34534-1-herve.codina@bootlin.com?part=2