PCI: Add support for PCIe-to-PCI bridge DMA alias quirks

Several PCIe-to-PCI bridges fail to provide a PCIe capability, causing us
to handle them as conventional PCI devices when they really use the
requester ID of the secondary bus.  We need to differentiate these from
PCIe-to-PCI bridges that actually use the conventional PCI ID when a PCIe
capability is not present, such as those found on the root complex of may
Intel chipsets.  Add a dev_flag bit to identify devices to be handled as
standard PCIe-to-PCI bridges.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

2 files changed, 10 insertions, 2 deletions

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 2c19f3f40621..df38f73f091f 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -88,8 +88,14 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
                                 continue;
                         }
                 } else {
-                        ret = fn(tmp, PCI_DEVID(tmp->bus->number, tmp->devfn),
-                                 data);
+                        if (tmp->dev_flags & PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS)
+                                ret = fn(tmp,
+                                         PCI_DEVID(tmp->subordinate->number,
+                                                   PCI_DEVFN(0, 0)), data);
+                        else
+                                ret = fn(tmp,
+                                         PCI_DEVID(tmp->bus->number,
+                                                   tmp->devfn), data);
                         if (ret)
                                 return ret;
                 }
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9d4035c276f4..85ab35e974a9 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -173,6 +173,8 @@ enum pci_dev_flags {
         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),
+        /* Use a PCIe-to-PCI bridge alias even if !pci_is_pcie */
+        PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS = (__force pci_dev_flags_t) (1 << 5),
 };
 
 enum pci_irq_reroute_variant {