Re: [PATCH v4 06/16] PCI: Quirk pci_for_each_dma_alias() for bridges

From: Bjorn Helgaas
Date: Wed May 28 2014 - 14:00:27 EST


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@xxxxxxxxxx>
> ---
> 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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