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

[Bjorn Andersson]

On Thu, Feb 01, 2024 at 04:55:29PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> 
> 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.

> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> ---
>  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?

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
>