diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index 849a0995d970..c563e4c8ff39 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -316,13 +316,15 @@ static inline struct iommu_table *find_iommu_table(struct device *dev)
 
 	pdev = to_pci_dev(dev);
 
+	/* search up the device tree for an iommu */
 	pbus = pdev->bus;
-
-	/* is the device behind a bridge? Look for the root bus */
-	while (pbus->parent)
+	do {
+		tbl = pci_iommu(pbus);
+		if (tbl && tbl->it_busno == pbus->number)
+			break;
+		tbl = NULL;
 		pbus = pbus->parent;
-
-	tbl = pci_iommu(pbus);
+	} while (pbus);
 
 	BUG_ON(tbl && (tbl->it_busno != pbus->number));