linux-kernel - Re: [PATCH 4/5] PCI/pwrctl: Move pwrctl device creation to its own helper function

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Message-ID: <20241025074827.fdkgyz3k767dgdqv@thinkpad>
Date: Fri, 25 Oct 2024 13:34:39 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	Abel Vesa <abel.vesa@...aro.org>,
	Stephan Gerhold <stephan.gerhold@...aro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Bjorn Andersson <bjorn.andersson@....qualcomm.com>
Subject: Re: [PATCH 4/5] PCI/pwrctl: Move pwrctl device creation to its own
 helper function

On Wed, Oct 23, 2024 at 12:23:57PM +0200, Bartosz Golaszewski wrote:
> On Tue, 22 Oct 2024 at 12:28, Manivannan Sadhasivam via B4 Relay
> <devnull+manivannan.sadhasivam.linaro.org@...nel.org> wrote:
> >
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> >
> > This makes the pci_bus_add_device() API easier to maintain. Also add more
> > comments to the helper to describe how the devices are created.
> >
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/bus.c | 59 ++++++++++++++++++++++++++++++++++++++-----------------
> >  1 file changed, 41 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> > index 351af581904f..c4cae1775c9e 100644
> > --- a/drivers/pci/bus.c
> > +++ b/drivers/pci/bus.c
> > @@ -321,6 +321,46 @@ void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }
> >
> >  void __weak pcibios_bus_add_device(struct pci_dev *pdev) { }
> >
> > +/*
> > + * Create pwrctl devices (if required) for the PCI devices to handle the power
> > + * state.
> > + */
> > +static void pci_pwrctl_create_devices(struct pci_dev *dev)
> > +{
> > +       struct device_node *np = dev_of_node(&dev->dev);
> > +       struct device *parent = &dev->dev;
> > +       struct platform_device *pdev;
> > +
> > +       /*
> > +        * First ensure that we are starting from a PCI bridge and it has a
> > +        * corresponding devicetree node.
> > +        */
> > +       if (np && pci_is_bridge(dev)) {
> > +               /*
> > +                * Now look for the child PCI device nodes and create pwrctl
> > +                * devices for them. The pwrctl device drivers will manage the
> > +                * power state of the devices.
> > +                */
> > +               for_each_child_of_node_scoped(np, child) {
> > +                       /*
> > +                        * First check whether the pwrctl device really needs to
> > +                        * be created or not. This is decided based on at least
> > +                        * one of the power supplies being defined in the
> > +                        * devicetree node of the device.
> > +                        */
> > +                       if (!of_pci_is_supply_present(child)) {
> > +                               pci_dbg(dev, "skipping OF node: %s\n", child->name);
> > +                               return;
> > +                       }
> > +
> > +                       /* Now create the pwrctl device */
> > +                       pdev = of_platform_device_create(child, NULL, parent);
> > +                       if (!pdev)
> > +                               pci_err(dev, "failed to create OF node: %s\n", child->name);
> > +               }
> > +       }
> > +}
> > +
> >  /**
> >   * pci_bus_add_device - start driver for a single device
> >   * @dev: device to add
> > @@ -345,24 +385,7 @@ void pci_bus_add_device(struct pci_dev *dev)
> >         pci_proc_attach_device(dev);
> >         pci_bridge_d3_update(dev);
> >
> > -       if (dev_of_node(&dev->dev) && pci_is_bridge(dev)) {
> > -               for_each_child_of_node_scoped(dn, child) {
> > -                       /*
> > -                        * First check whether the pwrctl device needs to be
> > -                        * created or not. This is decided based on at least
> > -                        * one of the power supplies being defined in the
> > -                        * devicetree node of the device.
> > -                        */
> > -                       if (!of_pci_is_supply_present(child)) {
> > -                               pci_dbg(dev, "skipping OF node: %s\n", child->name);
> > -                               continue;
> > -                       }
> > -
> > -                       pdev = of_platform_device_create(child, NULL, &dev->dev);
> > -                       if (!pdev)
> > -                               pci_err(dev, "failed to create OF node: %s\n", child->name);
> > -               }
> > -       }
> > +       pci_pwrctl_create_devices(dev);
> >
> >         /*
> >          * Create a device link between the PCI device and pwrctl device (if
> >
> > --
> > 2.25.1
> >
> >
> 
> Would it be possible to move this into drivers/pwrctl/ and provide a
> header stub for when PCI_PWRCTL is disabled in Kconfig?
> 

Unfortunately, no. Because the pwrctl drivers are modular and PCI core is
built-in. So if we use the pwrctl APIs in PCI core, then it will require pwrctl
to always be built-in, which we do not want.

- Mani

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