1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index c6e79d01ce3d..b001b5922e33 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -14,6 +14,40 @@
 #include "pci.h"
 
 DECLARE_RWSEM(pci_bus_sem);
+/*
+ * find the upstream PCIE-to-PCI bridge of a PCI device
+ * if the device is PCIE, return NULL
+ * if the device isn't connected to a PCIE bridge (that is its parent is a
+ * legacy PCI bridge and the bridge is directly connected to bus 0), return its
+ * parent
+ */
+struct pci_dev *
+pci_find_upstream_pcie_bridge(struct pci_dev *pdev)
+{
+        struct pci_dev *tmp = NULL;
+
+        if (pdev->is_pcie)
+                return NULL;
+        while (1) {
+                if (!pdev->bus->self)
+                        break;
+                pdev = pdev->bus->self;
+                /* a p2p bridge */
+                if (!pdev->is_pcie) {
+                        tmp = pdev;
+                        continue;
+                }
+                /* PCI device should connect to a PCIE bridge */
+                if (pdev->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE) {
+                        /* Busted hardware? */
+                        WARN_ON_ONCE(1);
+                        return NULL;
+                }
+                return pdev;
+        }
+
+        return tmp;
+}
 
 static struct pci_bus *pci_do_find_bus(struct pci_bus *bus, unsigned char busnr)
 {