1 files changed, 64 insertions, 13 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ea6c1762d5c8..50cd9c17c08f 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -586,16 +586,9 @@ static void pci_release_host_bridge_dev(struct device *dev)
 	kfree(to_pci_host_bridge(dev));
 }
 
-struct pci_host_bridge *pci_alloc_host_bridge(size_t priv)
+static void pci_init_host_bridge(struct pci_host_bridge *bridge)
 {
-	struct pci_host_bridge *bridge;
-
-	bridge = kzalloc(sizeof(*bridge) + priv, GFP_KERNEL);
-	if (!bridge)
-		return NULL;
-
 	INIT_LIST_HEAD(&bridge->windows);
-	bridge->dev.release = pci_release_host_bridge_dev;
 
 	/*
 	 * We assume we can manage these PCIe features.  Some systems may
@@ -608,6 +601,18 @@ struct pci_host_bridge *pci_alloc_host_bridge(size_t priv)
 	bridge->native_shpc_hotplug = 1;
 	bridge->native_pme = 1;
 	bridge->native_ltr = 1;
+}
+
+struct pci_host_bridge *pci_alloc_host_bridge(size_t priv)
+{
+	struct pci_host_bridge *bridge;
+
+	bridge = kzalloc(sizeof(*bridge) + priv, GFP_KERNEL);
+	if (!bridge)
+		return NULL;
+
+	pci_init_host_bridge(bridge);
+	bridge->dev.release = pci_release_host_bridge_dev;
 
 	return bridge;
 }
@@ -622,7 +627,7 @@ struct pci_host_bridge *devm_pci_alloc_host_bridge(struct device *dev,
 	if (!bridge)
 		return NULL;
 
-	INIT_LIST_HEAD(&bridge->windows);
+	pci_init_host_bridge(bridge);
 	bridge->dev.release = devm_pci_release_host_bridge_dev;
 
 	return bridge;
@@ -1081,6 +1086,36 @@ static void pci_enable_crs(struct pci_dev *pdev)
 
 static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
 					      unsigned int available_buses);
+/**
+ * pci_ea_fixed_busnrs() - Read fixed Secondary and Subordinate bus
+ * numbers from EA capability.
+ * @dev: Bridge
+ * @sec: updated with secondary bus number from EA
+ * @sub: updated with subordinate bus number from EA
+ *
+ * If @dev is a bridge with EA capability, update @sec and @sub with
+ * fixed bus numbers from the capability and return true.  Otherwise,
+ * return false.
+ */
+static bool pci_ea_fixed_busnrs(struct pci_dev *dev, u8 *sec, u8 *sub)
+{
+	int ea, offset;
+	u32 dw;
+
+	if (dev->hdr_type != PCI_HEADER_TYPE_BRIDGE)
+		return false;
+
+	/* find PCI EA capability in list */
+	ea = pci_find_capability(dev, PCI_CAP_ID_EA);
+	if (!ea)
+		return false;
+
+	offset = ea + PCI_EA_FIRST_ENT;
+	pci_read_config_dword(dev, offset, &dw);
+	*sec =  dw & PCI_EA_SEC_BUS_MASK;
+	*sub = (dw & PCI_EA_SUB_BUS_MASK) >> PCI_EA_SUB_BUS_SHIFT;
+	return true;
+}
 
 /*
  * pci_scan_bridge_extend() - Scan buses behind a bridge
@@ -1115,6 +1150,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 	u16 bctl;
 	u8 primary, secondary, subordinate;
 	int broken = 0;
+	bool fixed_buses;
+	u8 fixed_sec, fixed_sub;
+	int next_busnr;
 
 	/*
 	 * Make sure the bridge is powered on to be able to access config
@@ -1214,17 +1252,24 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 		/* Clear errors */
 		pci_write_config_word(dev, PCI_STATUS, 0xffff);
 
+		/* Read bus numbers from EA Capability (if present) */
+		fixed_buses = pci_ea_fixed_busnrs(dev, &fixed_sec, &fixed_sub);
+		if (fixed_buses)
+			next_busnr = fixed_sec;
+		else
+			next_busnr = max + 1;
+
 		/*
 		 * Prevent assigning a bus number that already exists.
 		 * This can happen when a bridge is hot-plugged, so in this
 		 * case we only re-scan this bus.
 		 */
-		child = pci_find_bus(pci_domain_nr(bus), max+1);
+		child = pci_find_bus(pci_domain_nr(bus), next_busnr);
 		if (!child) {
-			child = pci_add_new_bus(bus, dev, max+1);
+			child = pci_add_new_bus(bus, dev, next_busnr);
 			if (!child)
 				goto out;
-			pci_bus_insert_busn_res(child, max+1,
+			pci_bus_insert_busn_res(child, next_busnr,
 						bus->busn_res.end);
 		}
 		max++;
@@ -1285,7 +1330,13 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 			max += i;
 		}
 
-		/* Set subordinate bus number to its real value */
+		/*
+		 * Set subordinate bus number to its real value.
+		 * If fixed subordinate bus number exists from EA
+		 * capability then use it.
+		 */
+		if (fixed_buses)
+			max = fixed_sub;
 		pci_bus_update_busn_res_end(child, max);
 		pci_write_config_byte(dev, PCI_SUBORDINATE_BUS, max);
 	}