PCI: Add support for DMA alias quirks

Some devices are broken and use a requester ID other than their physical
devfn.  Add a byte, using an existing gap in the pci_dev structure, to
store an alternate "alias" devfn.  A bit in the dev_flags tells us when
this is valid.  We then add the alias as one more step in the
pci_for_each_dma_alias() iterator.

Tested-by: George Spelvin <linux@horizon.com>
Tested-by: Pat Erley <pat-lkml@erley.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 5601cdb8bbb3..2c19f3f40621 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -37,6 +37,17 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
         if (ret)
                 return ret;
 
+        /*
+         * If the device is broken and uses an alias requester ID for
+         * DMA, iterate over that too.
+         */
+        if (unlikely(pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN)) {
+                ret = fn(pdev, PCI_DEVID(pdev->bus->number,
+                                         pdev->dma_alias_devfn), data);
+                if (ret)
+                        return ret;
+        }
+
         for (bus = pdev->bus; !pci_is_root_bus(bus); bus = bus->parent) {
                 struct pci_dev *tmp;
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 545903df00dc..9d4035c276f4 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -171,6 +171,8 @@ enum pci_dev_flags {
         PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) (1 << 2),
         /* Flag for quirk use to store if quirk-specific ACS is enabled */
         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),
 };
 
 enum pci_irq_reroute_variant {
@@ -268,6 +270,7 @@ struct pci_dev {
         u8              rom_base_reg;   /* which config register controls the ROM */
         u8              pin;            /* which interrupt pin this device uses */
         u16             pcie_flags_reg; /* cached PCIe Capabilities Register */
+        u8              dma_alias_devfn;/* devfn of DMA alias, if any */
 
         struct pci_driver *driver;      /* which driver has allocated this device */
         u64             dma_mask;       /* Mask of the bits of bus address this