[PATCH v9 4/4] 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 | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-bus.c
index 23ac18551fd9..569580788575 100644
--- a/drivers/bus/simple-pm-bus.c
+++ b/drivers/bus/simple-pm-bus.c
@@ -26,6 +26,12 @@ static void simple_pm_bus_depopulate(void *data)
 {
 	struct device *dev = data;
 
+	if (!pm_runtime_enabled(dev)) {
+		/* No PM runtime, we can directly depopulate */
+		of_platform_depopulate(dev);
+		return;
+	}
+
 	/*
 	 * Bus stays on for children
 	 * This ensure that the bus will not be put in idle asynchronously when
@@ -83,16 +89,23 @@ 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;
-		else
+		if (of_property_match_string(np, "compatible", match->compatible))
 			return -ENODEV;
+
+		dev_dbg(&pdev->dev, "%s: populate only\n", __func__);
+
+		ret = simple_pm_bus_populate(&pdev->dev, lookup);
+		if (ret)
+			return dev_err_probe(&pdev->dev, ret, "failed to populate\n");
+
+		return 0;
 	}
 
 	bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
-- 
2.56.0