linux-kernel - Re: [PATCH] PCI: merge slot and bus reset implementations

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Date:   Thu, 1 Apr 2021 15:27:37 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Raphael Norwitz <raphael.norwitz@...anix.com>
Cc:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "ameynarkhede03@...il.com" <ameynarkhede03@...il.com>
Subject: Re: [PATCH] PCI: merge slot and bus reset implementations

On Thu, Apr 01, 2021 at 05:37:16AM +0000, Raphael Norwitz wrote:
> Slot resets are bus resets with additional logic to prevent a device
> from being removed during the reset. Currently slot and bus resets have
> separate implementations in pci.c, complicating higher level logic. As
> discussed on the mailing list, they should be combined into a generic
> function which performs an SBR. This change adds a function,
> pci_reset_bus_function(), which first attempts a slot reset and then
> attempts a bus reset if -ENOTTY is returned, such that there is now a
> single device agnostic function to perform an SBR.
> 
> This new function is also needed to add SBR reset quirks and therefore
> is exposed in pci.h.
> 
> Link: https://lkml.org/lkml/2021/3/23/911
> 
> Suggested-by: Alex Williamson <alex.williamson@...hat.com>
> Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
> Signed-off-by: Raphael Norwitz <raphael.norwitz@...anix.com>
> ---
>  drivers/pci/pci.c   | 17 +++++++++--------
>  include/linux/pci.h |  1 +
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 16a17215f633..12a91af2ade4 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4982,6 +4982,13 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, int probe)
>  	return pci_reset_hotplug_slot(dev->slot->hotplug, probe);
>  }
>  
> +int pci_reset_bus_function(struct pci_dev *dev, int probe)
> +{
> +	int rc = pci_dev_reset_slot_function(dev, probe);
> +
> +	return (rc == -ENOTTY) ? pci_parent_bus_reset(dev, probe) : rc;

The previous coding style is preferable one in the Linux kernel.
int rc = pci_dev_reset_slot_function(dev, probe);
if (rc != -ENOTTY)
  return rc;
return pci_parent_bus_reset(dev, probe);


> +}
> +
>  static void pci_dev_lock(struct pci_dev *dev)
>  {
>  	pci_cfg_access_lock(dev);
> @@ -5102,10 +5109,7 @@ int __pci_reset_function_locked(struct pci_dev *dev)
>  	rc = pci_pm_reset(dev, 0);
>  	if (rc != -ENOTTY)
>  		return rc;
> -	rc = pci_dev_reset_slot_function(dev, 0);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	return pci_parent_bus_reset(dev, 0);
> +	return pci_reset_bus_function(dev, 0);
>  }
>  EXPORT_SYMBOL_GPL(__pci_reset_function_locked);
>  
> @@ -5135,13 +5139,10 @@ int pci_probe_reset_function(struct pci_dev *dev)
>  	if (rc != -ENOTTY)
>  		return rc;
>  	rc = pci_pm_reset(dev, 1);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pci_dev_reset_slot_function(dev, 1);
>  	if (rc != -ENOTTY)
>  		return rc;
>  
> -	return pci_parent_bus_reset(dev, 1);
> +	return pci_reset_bus_function(dev, 1);
>  }
>  
>  /**
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 86c799c97b77..979d54335ac1 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1228,6 +1228,7 @@ int pci_probe_reset_bus(struct pci_bus *bus);
>  int pci_reset_bus(struct pci_dev *dev);
>  void pci_reset_secondary_bus(struct pci_dev *dev);
>  void pcibios_reset_secondary_bus(struct pci_dev *dev);
> +int pci_reset_bus_function(struct pci_dev *dev, int probe);
>  void pci_update_resource(struct pci_dev *dev, int resno);
>  int __must_check pci_assign_resource(struct pci_dev *dev, int i);
>  int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
> -- 
> 2.20.1