1 files changed, 47 insertions, 9 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 446e4a94d7d3..dd64310a735e 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1081,6 +1081,37 @@ struct pci_dev *__ref pci_scan_single_device(struct pci_bus *bus, int devfn)
 }
 EXPORT_SYMBOL(pci_scan_single_device);
 
+static unsigned next_ari_fn(struct pci_dev *dev, unsigned fn)
+{
+	u16 cap;
+	unsigned pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
+	if (!pos)
+		return 0;
+	pci_read_config_word(dev, pos + 4, &cap);
+	return cap >> 8;
+}
+
+static unsigned next_trad_fn(struct pci_dev *dev, unsigned fn)
+{
+	return (fn + 1) % 8;
+}
+
+static unsigned no_next_fn(struct pci_dev *dev, unsigned fn)
+{
+	return 0;
+}
+
+static int only_one_child(struct pci_bus *bus)
+{
+	struct pci_dev *parent = bus->self;
+	if (!parent || !pci_is_pcie(parent))
+		return 0;
+	if (parent->pcie_type == PCI_EXP_TYPE_ROOT_PORT ||
+	    parent->pcie_type == PCI_EXP_TYPE_DOWNSTREAM)
+		return 1;
+	return 0;
+}
+
 /**
  * pci_scan_slot - scan a PCI slot on a bus for devices.
  * @bus: PCI bus to scan
@@ -1094,21 +1125,28 @@ EXPORT_SYMBOL(pci_scan_single_device);
  */
 int pci_scan_slot(struct pci_bus *bus, int devfn)
 {
-	int fn, nr = 0;
+	unsigned fn, nr = 0;
 	struct pci_dev *dev;
+	unsigned (*next_fn)(struct pci_dev *, unsigned) = no_next_fn;
+
+	if (only_one_child(bus) && (devfn > 0))
+		return 0; /* Already scanned the entire slot */
 
 	dev = pci_scan_single_device(bus, devfn);
 	if (dev && !dev->is_added)	/* new device? */
 		nr++;
 
-	if (dev && dev->multifunction) {
-		for (fn = 1; fn < 8; fn++) {
-			dev = pci_scan_single_device(bus, devfn + fn);
-			if (dev) {
-				if (!dev->is_added)
-					nr++;
-				dev->multifunction = 1;
-			}
+	if (pci_ari_enabled(bus))
+		next_fn = next_ari_fn;
+	else if (dev && dev->multifunction)
+		next_fn = next_trad_fn;
+
+	for (fn = next_fn(dev, 0); fn > 0; fn = next_fn(dev, fn)) {
+		dev = pci_scan_single_device(bus, devfn + fn);
+		if (dev) {
+			if (!dev->is_added)
+				nr++;
+			dev->multifunction = 1;
 		}
 	}