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    SubjectRe: [PATCH 1/5] pci: Add PCI DMA source ID quirk
    Hi Alex,

    >DMA transactions are tagged with the source ID of the device making
    >the request. Occasionally hardware screws this up and uses the
    >source ID of a different device (often the wrong function number of
    >a multifunction device). A specific Ricoh multifunction device is
    >a prime example of this problem and included in this patch. The
    >purpose of this function is that given a pci_dev, return the pci_dev
    >to use as the source ID for DMA. When hardware works correctly,
    >this returns the input device. For the components of the Ricoh
    >multifunction device, return the pci_dev for function 0.
    >
    >This will be used by IOMMU drivers for determining the boundaries
    >of IOMMU groups as multiple devices using the same source ID must
    >be contained within the same group. This can also be used by
    >existing streaming DMA paths for the same purpose.
    >
    >Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
    >---
    >
    > drivers/pci/quirks.c | 40 ++++++++++++++++++++++++++++++++++++++++
    > include/linux/pci.h | 5 +++++
    > 2 files changed, 45 insertions(+)
    >
    >diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
    >index 2a75216..004e167 100644
    >--- a/drivers/pci/quirks.c
    >+++ b/drivers/pci/quirks.c
    >@@ -3179,3 +3179,43 @@ int pci_dev_specific_reset(struct pci_dev *dev, int probe)
    >
    > return -ENOTTY;
    > }
    >+
    >+static struct pci_dev *pci_func_0_dma_source(struct pci_dev *dev)
    >+{
    >+ return pci_get_slot(dev->bus, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
    >+}

    I think we needn't retrieve the PCI device passed in again from the list
    of PCI devices if its function number is zero.

    if (!PCI_FUNC(dev->devfn))
    return dev;

    Thanks,
    Gavin

    >+
    >+static const struct pci_dev_dma_source {
    >+ u16 vendor;
    >+ u16 device;
    >+ struct pci_dev *(*dma_source)(struct pci_dev *dev);
    >+} pci_dev_dma_source[] = {
    >+ /*
    >+ * https://bugzilla.redhat.com/show_bug.cgi?id=605888
    >+ *
    >+ * Some Ricoh devices use the function 0 source ID for DMA on
    >+ * other functions of a multifunction device. The DMA devices
    >+ * is therefore function 0, which will have implications of the
    >+ * iommu grouping of these devices.
    >+ */
    >+ { PCI_VENDOR_ID_RICOH, 0xe822, pci_func_0_dma_source },
    >+ { PCI_VENDOR_ID_RICOH, 0xe230, pci_func_0_dma_source },
    >+ { PCI_VENDOR_ID_RICOH, 0xe832, pci_func_0_dma_source },
    >+ { PCI_VENDOR_ID_RICOH, 0xe832, pci_func_0_dma_source },
    >+ { 0 }
    >+};
    >+
    >+struct pci_dev *pci_dma_source(struct pci_dev *dev)
    >+{
    >+ const struct pci_dev_dma_source *i;
    >+
    >+ for (i = pci_dev_dma_source; i->dma_source; i++) {
    >+ if ((i->vendor == dev->vendor ||
    >+ i->vendor == (u16)PCI_ANY_ID) &&
    >+ (i->device == dev->device ||
    >+ i->device == (u16)PCI_ANY_ID))
    >+ return i->dma_source(dev);
    >+ }
    >+
    >+ return dev;
    >+}
    >diff --git a/include/linux/pci.h b/include/linux/pci.h
    >index d8c379d..5bc7502 100644
    >--- a/include/linux/pci.h
    >+++ b/include/linux/pci.h
    >@@ -1486,9 +1486,14 @@ enum pci_fixup_pass {
    >
    > #ifdef CONFIG_PCI_QUIRKS
    > void pci_fixup_device(enum pci_fixup_pass pass, struct pci_dev *dev);
    >+struct pci_dev *pci_dma_source(struct pci_dev *dev);
    > #else
    > static inline void pci_fixup_device(enum pci_fixup_pass pass,
    > struct pci_dev *dev) {}
    >+static inline struct pci_dev *pci_dma_source(struct pci_dev *dev)
    >+{
    >+ return dev;
    >+}
    > #endif
    >
    > void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);
    >
    >--
    >To unsubscribe from this list: send the line "unsubscribe linux-pci" in
    >the body of a message to majordomo@vger.kernel.org
    >More majordomo info at http://vger.kernel.org/majordomo-info.html
    >



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