linux-kernel - Re: [PATCH v4 06/16] PCI: Quirk pci_for_each_dma

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Message-ID: <20140528180018.GS11907@google.com>
Date:	Wed, 28 May 2014 12:00:18 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org,
	acooks@...il.com, linux-kernel@...r.kernel.org, eddy0596@...il.com,
	linux@...izon.com
Subject: Re: [PATCH v4 06/16] PCI: Quirk pci_for_each_dma_alias() for bridges

On Thu, May 22, 2014 at 05:08:01PM -0600, Alex Williamson wrote:
> Several PCIe-to-PCI bridges fail to provide a PCIe capability, causing
> us to handle them as conventional PCI devices.  In some cases, this
> may be correct, in others it's not.  Add a dev_flag bit to identify
> devices to be handled as standard PCIe-to-PCI bridges.

Can you expand on the "in some cases, this may be correct, in others it's
not"?  Do you mean that for some *devices* it's correct to handle them as
conventional PCI, or in some *situations* it's correct?  Something else?

I'd like to either remove that sentence or add a little more information to
make it useful.

I guess this probably goes along with the tests in
quirk_use_pcie_bridge_dma_alias().

> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>  drivers/pci/search.c |   10 ++++++++--
>  include/linux/pci.h  |    2 ++
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index 2c19f3f..df38f73 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -88,8 +88,14 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
>  				continue;
>  			}
>  		} else {
> -			ret = fn(tmp, PCI_DEVID(tmp->bus->number, tmp->devfn),
> -				 data);
> +			if (tmp->dev_flags & PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS)
> +				ret = fn(tmp,
> +					 PCI_DEVID(tmp->subordinate->number,
> +						   PCI_DEVFN(0, 0)), data);
> +			else
> +				ret = fn(tmp,
> +					 PCI_DEVID(tmp->bus->number,
> +						   tmp->devfn), data);
>  			if (ret)
>  				return ret;
>  		}
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 9d4035c..85ab35e 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -173,6 +173,8 @@ enum pci_dev_flags {
>  	PCI_DEV_FLAGS_ACS_ENABLED_QUIRK = (__force pci_dev_flags_t) (1 << 3),
>  	/* Flag to indicate the device uses dma_alias_devfn */
>  	PCI_DEV_FLAGS_DMA_ALIAS_DEVFN = (__force pci_dev_flags_t) (1 << 4),
> +	/* Use a PCIe-to-PCI bridge alias even if !pci_is_pcie */
> +	PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS = (__force pci_dev_flags_t) (1 << 5),
>  };
>  
>  enum pci_irq_reroute_variant {
> 
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