On Sun, May 08, 2016 at 03:03:21PM +0530, Jayachandran C wrote:
> The Broadcom Vulcan PCI topology is slightly unusual, for a multi-node
> system, it looks like:
>
> [bus 0]
> |
> +--[node 0 PCI bridge 0.0.0]
> | |
> | [bus 1]
> | +---[SoC PCI devices 1.4.x, 1.5.x] ........
> | +---[Glue bridges 1.a.x, 1.b.x] \
> | | .....{node 0 GIC ITS}
> | | /
> | +----[SoC PCIe controller root ports]
> | | \...... {SMMUv3 0..3}
> | |
> | +---- [external PCI devices]
> +- [node 1 PCI bridge 0.0.1]
> | |
> | [bus n - similar to bus 1 above]
> ...
>
> The for_each_dma_alias call for external PCI devices should not go
> beyond the PCIe controllers where the SMMU and ITS is associated, going
> further above to the glue bridges or the node bridges will find aliases
> which are not valid. For internal devices, the association is at the
> node level bridge and the alias search should not go further.
I like the line of reasoning that we should not iterate higher in the
hierarchy than where the translation hardware is attached. That seems
like a reasonable thing in general, not just for this hardware.
Is there some generic way to learn where the translation hardware is
attached? If there is, we could make pci_for_each_dma_alias() use
that information, and maybe we could solve the problem for other
systems as well as for Vulcan.
> To handle this quirk, we mark the SoC PCIe bridges and node PCI bridge
> with flag PCI_DEV_FLAGS_DMA_ALIAS_ROOT so that the alias and RID
> calculations are correct.
>
> Signed-off-by: Jayachandran C <jchandra@xxxxxxxxxxxx>
> ---
> drivers/pci/quirks.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 8e67802..62664b5 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3734,6 +3734,20 @@ DECLARE_PCI_FIXUP_HEADER(0x1283, 0x8892, quirk_use_pcie_bridge_dma_alias);
> DECLARE_PCI_FIXUP_HEADER(0x8086, 0x244e, quirk_use_pcie_bridge_dma_alias);
>
> /*
> + * The IOMMU and interrupt controller of Broadcom vulcan are associated
> + * not at the root bus, but at a bridge below. The DMA alias search should
> + * not go above the bridge at which the association exists.
> + */
> +static void quirk_bridge_brcm_vulcan_pcie_root(struct pci_dev *pdev)
> +{
> + pdev->dev_flags |= PCI_DEV_FLAGS_DMA_ALIAS_ROOT;
> +}
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_BROADCOM, 0x9000,
> + quirk_bridge_brcm_vulcan_pcie_root);
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_BROADCOM, 0x9084,
> + quirk_bridge_brcm_vulcan_pcie_root);
> +
> +/*
> * Intersil/Techwell TW686[4589]-based video capture cards have an empty (zero)
> * class code. Fix it.
> */
> --
> 1.9.1
>
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