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

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Message-ID: <CAMRc=MdXO6c6asvRSn_Z8-oFS48hroT+dazGKB6WWY1_Zu7f1Q@mail.gmail.com>
Date: Wed, 10 Jan 2024 13:55:18 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Lukas Wunner <lukas@...ner.de>
Cc: Kalle Valo <kvalo@...nel.org>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Heiko Stuebner <heiko@...ech.de>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Chris Morgan <macromorgan@...mail.com>, 
	Linus Walleij <linus.walleij@...aro.org>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	Arnd Bergmann <arnd@...db.de>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Nícolas F . R . A . Prado <nfraprado@...labora.com>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Peng Fan <peng.fan@....com>, 
	Robert Richter <rrichter@....com>, Dan Williams <dan.j.williams@...el.com>, 
	Jonathan Cameron <Jonathan.Cameron@...wei.com>, Terry Bowman <terry.bowman@....com>, 
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Huacai Chen <chenhuacai@...nel.org>, Alex Elder <elder@...aro.org>, 
	Srini Kandagatla <srinivas.kandagatla@...aro.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-wireless@...r.kernel.org, 
	netdev@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFC 3/9] PCI/portdrv: create platform devices for child OF nodes

On Tue, Jan 9, 2024 at 3:43 PM Lukas Wunner <lukas@...ner.de> 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
>