Re: [RFC 3/9] PCI/portdrv: create platform devices for child OF nodes

[Bartosz Golaszewski]

On Tue, Jan 9, 2024 at 3:43 PM Lukas Wunner <lukas@xxxxxxxxx> wrote:
>
> On Thu, Jan 04, 2024 at 02:01:17PM +0100, Bartosz Golaszewski wrote:
> > In order to introduce PCIe power-sequencing, we need to create platform
> > devices for child nodes of the port driver node. They will get matched
> > against the pwrseq drivers (if one exists) and then the actuak PCIe
> > device will reuse the node once it's detected on the bus.
> [...]
> > --- a/drivers/pci/pcie/portdrv.c
> > +++ b/drivers/pci/pcie/portdrv.c
> > @@ -715,7 +716,7 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
> >               pm_runtime_allow(&dev->dev);
> >       }
> >
> > -     return 0;
> > +     return devm_of_platform_populate(&dev->dev);
> >  }
>
> I think this belongs in of_pci_make_dev_node(), portdrv seems totally
> the wrong place.  Note that you're currently calling this for RCECs
> (Root Complex Event Collectors) as well, which is likely not what
> you want.
>

of_pci_make_dev_node() is only called when the relevant PCI device is
instantiated which doesn't happen until it's powered-up and scanned -
precisely the problem I'm trying to address.

Calling this for whomever isn't really a problem though, is it? We
will create a platform device alright - if it's defined on the DT -
and at worst it won't match against any driver. It seems harmless IMO.

> devm functions can't be used in the PCI core, so symmetrically call
> of_platform_unpopulate() from of_pci_remove_node().

I don't doubt what you're saying is true (I've seen worse things) but
this is the probe() callback of a driver using the driver model. Why
wouldn't devres work?

Bart

>
> Thanks,
>
> Lukas
>