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

[Herve Codina <herve.codina@bootlin.com>]

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