linux-kernel - Re: [PATCH v3 1/2] PCI: don't rely on of_platform

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Message-ID: <20240823221021.GA388724@bhelgaas>
Date: Fri, 23 Aug 2024 17:10:21 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>, Rob Herring <robh+dt@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Krishna chaitanya chundru <quic_krichai@...cinc.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v3 1/2] PCI: don't rely on of_platform_depopulate() for
 reused OF-nodes

[+to Rob]

On Fri, Aug 23, 2024 at 11:33:22AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> of_platform_depopulate() doesn't play nice with reused OF nodes - it
> ignores the ones that are not marked explicitly as populated and it may
> happen that the PCI device goes away before the platform device in which
> case the PCI core clears the OF_POPULATED bit. We need to
> unconditionally unregister the platform devices for child nodes when
> stopping the PCI device.

Rob, any concerns with this?

> Fixes: 8fb18619d910 ("PCI/pwrctl: Create platform devices for child OF nodes of the port node")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> ---
>  drivers/pci/remove.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 910387e5bdbf..4770cb87e3f0 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -1,7 +1,10 @@
>  // SPDX-License-Identifier: GPL-2.0
>  #include <linux/pci.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
>  #include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +
>  #include "pci.h"
>  
>  static void pci_free_resources(struct pci_dev *dev)
> @@ -14,12 +17,25 @@ static void pci_free_resources(struct pci_dev *dev)
>  	}
>  }
>  
> +static int pci_pwrctl_unregister(struct device *dev, void *data)
> +{
> +	struct device_node *pci_node = data, *plat_node = dev_of_node(dev);
> +
> +	if (dev_is_platform(dev) && plat_node && plat_node == pci_node) {
> +		of_device_unregister(to_platform_device(dev));
> +		of_node_clear_flag(plat_node, OF_POPULATED);
> +	}
> +
> +	return 0;
> +}
> +
>  static void pci_stop_dev(struct pci_dev *dev)
>  {
>  	pci_pme_active(dev, false);
>  
>  	if (pci_dev_is_added(dev)) {
> -		of_platform_depopulate(&dev->dev);
> +		device_for_each_child(dev->dev.parent, dev_of_node(&dev->dev),
> +				      pci_pwrctl_unregister);
>  		device_release_driver(&dev->dev);
>  		pci_proc_detach_device(dev);
>  		pci_remove_sysfs_dev_files(dev);
> -- 
> 2.43.0
>