linux-kernel - Re: [PATCH v15 7/9] PCI: Setup ACPI fwnode early and at the same time with OF

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Date:   Fri, 13 Aug 2021 18:04:28 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Amey Narkhede <ameynarkhede03@...il.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, alex.williamson@...hat.com,
        Raphael Norwitz <raphael.norwitz@...anix.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        kw@...ux.com, Shanker Donthineni <sdonthineni@...dia.com>,
        Sinan Kaya <okaya@...nel.org>, Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v15 7/9] PCI: Setup ACPI fwnode early and at the same
 time with OF

[+cc Ben, Mika]

On Thu, Aug 05, 2021 at 09:59:15PM +0530, Amey Narkhede wrote:
> From: Shanker Donthineni <sdonthineni@...dia.com>
> 
> The pci_dev objects are created through two mechanisms 1) during PCI
> bus scan and 2) from I/O Virtualization. The fwnode in pci_dev object
> is being set at different places depends on the type of firmware used,
> device creation mechanism, and acpi_pci_bridge_d3().
> 
> The software features which have a dependency on ACPI fwnode properties
> and need to be handled before device_add() will not work. One use case,
> the software has to check the existence of _RST method to support ACPI
> based reset method.
> 
> This patch does the two changes in order to provide fwnode consistently.
>  - Set ACPI and OF fwnodes from pci_setup_device().
>  - Remove pci_set_acpi_fwnode() in acpi_pci_bridge_d3().
> 
> After this patch, ACPI/OF firmware properties are visible at the same
> time during the early stage of pci_dev setup. And also call sites should
> be able to use firmware agnostic functions device_property_xxx() for the
> early PCI quirks in the future.
> 
> Signed-off-by: Shanker Donthineni <sdonthineni@...dia.com>
> Reviewed-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>  drivers/pci/pci-acpi.c | 1 -
>  drivers/pci/probe.c    | 7 ++++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index eaddbf701759..dae021322b3f 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -952,7 +952,6 @@ static bool acpi_pci_bridge_d3(struct pci_dev *dev)
>  		return false;
>  
>  	/* Assume D3 support if the bridge is power-manageable by ACPI. */
> -	pci_set_acpi_fwnode(dev);
>  	adev = ACPI_COMPANION(&dev->dev);

I *think* the Root Port code farther down in this function is also now
unnecessary:

  acpi_pci_bridge_d3(...)
  {
    ...
    root = pcie_find_root_port(dev);
    adev = ACPI_COMPANION(&root->dev);
    if (root == dev) {
      /*
       * It is possible that the ACPI companion is not yet bound
       * for the root port so look it up manually here.
       */
      if (!adev && !pci_dev_is_added(root))
        adev = acpi_pci_find_companion(&root->dev);
    }

Since we're now setting the ACPI_COMPANION for every pci_dev long
before we get here, I think this could now be simplified to something
like this:

  acpi_pci_bridge_d3(...)
  {
    if (!dev->is_hotplug_bridge)
      return false;

    adev = ACPI_COMPANION(&dev->dev);
    if (adev && acpi_device_power_manageable(adev))
      return true;

    root = pcie_find_root_port(dev);
    if (!root)
      return false;

    adev = ACPI_COMPANION(&root->dev);
    if (!adev)
      return false;

    rc = acpi_dev_get_property(dev, "HotPlugSupportInD3",
                               ACPI_TYPE_INTEGER, &val);
    if (rc < 0)
      return false;

    return val == 1;
  }

acpi_pci_bridge_d3() was added by 26ad34d510a8 ("PCI / ACPI: Whitelist
D3 for more PCIe hotplug ports") [1], so I cc'd Mika in case he has
any comment.

>  	if (adev && acpi_device_power_manageable(adev))
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 379e85037d9b..15a6975d3757 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1789,6 +1789,9 @@ int pci_setup_device(struct pci_dev *dev)
>  	dev->error_state = pci_channel_io_normal;
>  	set_pcie_port_type(dev);
>  
> +	pci_set_of_node(dev);
> +	pci_set_acpi_fwnode(dev);

Is there a reason why you moved pci_set_of_node() from
pci_scan_device() to here?  I think it's a good change; I'm just
curious if you tripped over something that required it.

The pci_set_of_node() was added to pci_scan_device() by 98d9f30c820d
("pci/of: Match PCI devices to OF nodes dynamically") [2], so I cc'd
Ben just in case there's some reason he didn't put it in
pci_setup_device() in the first place.

>  	pci_dev_assign_slot(dev);
>  
>  	/*
> @@ -1924,6 +1927,7 @@ int pci_setup_device(struct pci_dev *dev)
>  	default:				    /* unknown header */
>  		pci_err(dev, "unknown header type %02x, ignoring device\n",
>  			dev->hdr_type);
> +		pci_release_of_node(dev);
>  		return -EIO;
>  
>  	bad:
> @@ -2351,10 +2355,7 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
>  	dev->vendor = l & 0xffff;
>  	dev->device = (l >> 16) & 0xffff;
>  
> -	pci_set_of_node(dev);
> -
>  	if (pci_setup_device(dev)) {
> -		pci_release_of_node(dev);
>  		pci_bus_put(dev->bus);
>  		kfree(dev);
>  		return NULL;

[1] https://git.kernel.org/linus/26ad34d510a8
[2] https://git.kernel.org/linus/98d9f30c820d