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@xxxxxxxxxx>
>---
>
> 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);
>
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