[PATCH v2 05/26] bus: simple-pm-bus: Populate child nodes at probe

Herve Codina
2025-05-07T07:13:36Z

The simple-pm-bus drivers handles several simple bus. When it is used
with busses other than a compatible "simple-pm-bus", it don'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 | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
index d8e029e7e53f..93c6ba605d7a 100644
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -42,14 +42,14 @@ 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.
+ * have their child nodes populated automatically. So, don't need to
+ * do anything more except populate child nodes. 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 +64,14 @@ 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;
}

@@ -78,12 +79,16 @@ static void simple_pm_bus_remove(struct platform_device *pdev)
{
const void *data = of_device_get_match_data(&pdev->dev);

- if (pdev->driver_override || data)
+ if (pdev->driver_override)
return;

dev_dbg(&pdev->dev, "%s\n", __func__);

- pm_runtime_disable(&pdev->dev);
+ if (pdev->dev.of_node)
+ of_platform_depopulate(&pdev->dev);
+
+ if (!data)
+ pm_runtime_disable(&pdev->dev);
}

static int simple_pm_bus_runtime_suspend(struct device *dev)
--
2.49.0