linux-kernel - Re: [RFC 6/9] PCI: create platform devices for child OF nodes of the port node

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Date: Fri, 2 Feb 2024 10:03:19 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Konrad Dybcio <konrad.dybcio@...aro.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Marcel Holtmann <marcel@...tmann.org>, Luiz Augusto von Dentz <luiz.dentz@...il.com>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Alex Elder <elder@...aro.org>, Srini Kandagatla <srinivas.kandagatla@...aro.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, 
	Abel Vesa <abel.vesa@...aro.org>, Manivannan Sadhasivam <mani@...nel.org>, Lukas Wunner <lukas@...ner.de>, 
	linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org, 
	linux-pci@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFC 6/9] PCI: create platform devices for child OF nodes of the
 port node

On Fri, Feb 2, 2024 at 3:59 AM Bjorn Andersson <andersson@...nel.org> wrote:
>
> On Thu, Feb 01, 2024 at 04:55:29PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > In order to introduce PCI power-sequencing,
>
> Please provide a proper problem description.
>
> > we need to create platform
>
> And properly express why this is a "need".
>
> > devices for child nodes of the port node. They will get matched against
> > the pwrseq drivers
>
> That's not what happens in your code, the child nodes of the bridge node
> in DeviceTree will match against arbitrary platform_drivers.
>
> I also would like this commit message to express that the job of the
> matched device is to:
>
> 1) power up said device, followed by triggering a scan on the parent PCI
> bus during it's probe function.
>
> 2)  power down said device, during its remove function.
>
> > (if one exists) and then the actual PCI device will
> > reuse the node once it's detected on the bus.
>
> I think the "reuse" deserves to be clarified as there will be both a pci
> and a platform device associated with the same of_node.
>

Noted all of the above. Thanks!

> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
> >  drivers/pci/bus.c    | 9 ++++++++-
> >  drivers/pci/remove.c | 2 ++
> >  2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> > index 826b5016a101..17ab41094c4e 100644
> > --- a/drivers/pci/bus.c
> > +++ b/drivers/pci/bus.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/errno.h>
> >  #include <linux/ioport.h>
> >  #include <linux/of.h>
> > +#include <linux/of_platform.h>
> >  #include <linux/proc_fs.h>
> >  #include <linux/slab.h>
> >
> > @@ -342,8 +343,14 @@ void pci_bus_add_device(struct pci_dev *dev)
> >        */
> >       pcibios_bus_add_device(dev);
> >       pci_fixup_device(pci_fixup_final, dev);
> > -     if (pci_is_bridge(dev))
> > +     if (pci_is_bridge(dev)) {
> >               of_pci_make_dev_node(dev);
> > +             retval = of_platform_populate(dev->dev.of_node, NULL, NULL,
> > +                                           &dev->dev);
>
> I'm not familiar enough with the ins and outs of the PCI code. Can you
> confirm that there are no problems with this (possibly) calling
> pci_rescan_bus() before the bridge device is fully initialized below?
>

I'll clarify that. I'm not that well versed with PCI code either but
will get help from the right people.

Bart

> Regards,
> Bjorn
>
> > +             if (retval)
> > +                     pci_err(dev, "failed to populate child OF nodes (%d)\n",
> > +                             retval);
> > +     }
> >       pci_create_sysfs_dev_files(dev);
> >       pci_proc_attach_device(dev);
> >       pci_bridge_d3_update(dev);
> > diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> > index d749ea8250d6..fc9db2805888 100644
> > --- a/drivers/pci/remove.c
> > +++ b/drivers/pci/remove.c
> > @@ -1,6 +1,7 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <linux/pci.h>
> >  #include <linux/module.h>
> > +#include <linux/of_platform.h>
> >  #include "pci.h"
> >
> >  static void pci_free_resources(struct pci_dev *dev)
> > @@ -22,6 +23,7 @@ static void pci_stop_dev(struct pci_dev *dev)
> >               device_release_driver(&dev->dev);
> >               pci_proc_detach_device(dev);
> >               pci_remove_sysfs_dev_files(dev);
> > +             of_platform_depopulate(&dev->dev);
> >               of_pci_remove_node(dev);
> >
> >               pci_dev_assign_added(dev, false);
> > --
> > 2.40.1
> >