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>

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;
 		}

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 {