PCI: add PCI DMA source ID quirk

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.

Given a pci_dev, this function returns 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, it returns 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.

[bhelgaas: fold in pci_dev_get() for !CONFIG_PCI]
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/pci.h b/include/linux/pci.h
index d8c379dba6ad..39983be7b25b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1332,6 +1332,9 @@ static inline struct pci_dev *pci_get_bus_and_slot(unsigned int bus,
 static inline int pci_domain_nr(struct pci_bus *bus)
 { return 0; }
 
+static inline struct pci_dev *pci_dev_get(struct pci_dev *dev)
+{ return NULL; }
+
 #define dev_is_pci(d) (false)
 #define dev_is_pf(d) (false)
 #define dev_num_vf(d) (0)
@@ -1486,9 +1489,14 @@ 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_get_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_get_dma_source(struct pci_dev *dev)
+{
+        return pci_dev_get(dev);
+}
 #endif
 
 void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);