Re: [PATCH 1/2] PCI: use reset_root_port() for bus reset of devices on a root bus

[Bjorn Helgaas <helgaas@kernel.org>]

On Fri, Oct 16, 2026 at 07:59:39PM -0400, Hamza Mahfooz wrote:
> The "bus" reset method resets a device by asserting Secondary Bus Reset
> on its upstream bridge, so it is not available for a device on a root
> bus, which has no upstream bridge.
> 
> Some platforms have no Root Ports and expose PCI devices directly on a
> root bus, e.g., Hyper-V vPCI places each assigned PCI function directly
> on the root bus of a virtual host bridge. Such a device has no reset
> method at all if it supports neither FLR nor PM reset, even if the
> platform is able to reset it.
> 
> pci_host_bridge::reset_root_port() already allows a host bridge to reset
> a device on a root bus in a platform-specific way, so far only in place
> of a Secondary Bus Reset by a Root Port. Use it for the "bus" reset
> method of a device that is the only device on a root bus, and wait for
> the device to become ready afterwards, as is done for other reset
> methods.
> 
> Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>

Applied both to pci/reset for v7.5, thanks!

> ---
>  drivers/pci/pci.c | 32 ++++++++++++++++++++++++++++++--
>  1 file changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 8cc6a89130b5..fd4e958d6b99 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4924,18 +4924,46 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev)
>  }
>  EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset);
>  
> +static int pci_root_bus_reset(struct pci_dev *dev, bool probe)
> +{
> +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> +	int rc;
> +
> +	/*
> +	 * Bridges, e.g., Root Ports, are not eligible.  Check the header type
> +	 * because dev->subordinate is not set up yet when the reset methods
> +	 * are probed during enumeration.
> +	 */
> +	if (pci_is_bridge(dev) || !host->reset_root_port)
> +		return -ENOTTY;
> +
> +	if (probe)
> +		return 0;
> +
> +	rc = host->reset_root_port(host, dev);
> +	if (rc)
> +		return rc;
> +
> +	return pci_dev_wait(dev, "bus reset", PCIE_RESET_READY_POLL_MS);
> +}
> +
>  static int pci_parent_bus_reset(struct pci_dev *dev, bool probe)
>  {
>  	struct pci_dev *pdev;
>  
> -	if (pci_is_root_bus(dev->bus) || dev->subordinate ||
> -	    !dev->bus->self || dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
> +	if (dev->subordinate || dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
>  		return -ENOTTY;
>  
>  	list_for_each_entry(pdev, &dev->bus->devices, bus_list)
>  		if (pdev != dev)
>  			return -ENOTTY;
>  
> +	if (pci_is_root_bus(dev->bus))
> +		return pci_root_bus_reset(dev, probe);
> +
> +	if (!dev->bus->self)
> +		return -ENOTTY;
> +
>  	if (probe)
>  		return 0;
>  
> -- 
> 2.56.0
>