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

Hi Andy,

On Thu, 8 May 2025 17:27:52 +0300
Andy Shevchenko [off-list ref] wrote:

On Wed, May 07, 2025 at 09:12:47AM +0200, Herve Codina wrote:

quoted

The simple-pm-bus drivers handles several simple bus. When it is used  

bus --> busses ?

Yes sure.

quoted

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.  

...

quoted

 	if (match && match->data) {
 		if (of_property_match_string(np, "compatible", match->compatible) == 0)  

Side note, there is an fwnode_is_device_compatible() API for such cases. And IIRC
there is also OF variant of it.

fwnode_device_is_compatible() checked for all compatible string. I mean, if
we have compatible = "foo,custom-bus", "simple-bus";
fwnode_device_is_compatible() checking against "simple-bus" returns true.

Here, we want "simple-bus" as the first position in the compatible string.
In other word, we want to match the more specific compatible string as
mentioned in the comment.

quoted

-			return 0;
+			goto populate;
 		else
 			return -ENODEV;
 	}  

...

quoted

+	if (pdev->dev.of_node)  

Why do you need this check? AFAICS it dups the one the call has already in it.

of_platform_populate() was called only if an OF node is present.
I want to call of_platform_depopulate() on removal also only if an OF node
is present.

I don't see the other call that duplicated this check.

Can you clarify?

quoted

+		of_platform_depopulate(&pdev->dev);  

Best regards,
Hervé