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

Herve Codina
2025-05-19T11:58:23Z

Hi Andy,

On Thu, 8 May 2025 17:27:52 +0300
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Wed, May 07, 2025 at 09:12:47AM +0200, Herve Codina wrote:
> > The simple-pm-bus drivers handles several simple bus. When it is used
>
> bus --> busses ?

Yes sure.

>
> > 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.
>
> ...
>
> > 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.

>
> > - return 0;
> > + goto populate;
> > else
> > return -ENODEV;
> > }
>
> ...
>
> > + 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?

>
> > + of_platform_depopulate(&pdev->dev);
>

Best regards,
Hervé