[MIPS] IP27: Switch to dynamic interrupt routing avoding panic on error.

pcibios_map_irq is no way of returning an error but on IP27 an interrupt
is possibly not routable when running out of resources.  So do the
interrupt routing at pcibios_enable_device time.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pci/pci-ip27.c

@@ -142,26 +142,48 @@ int __cpuinit bridge_probe(nasid_t nasid, int widget_id, int masterwid)
  * on any one of the hubs connected to its xbow.
  */
 int __devinit pcibios_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
+{
+	return 0;
+}
+
+/* Most MIPS systems have straight-forward swizzling needs.  */
+static inline u8 bridge_swizzle(u8 pin, u8 slot)
+{
+	return (((pin - 1) + slot) % 4) + 1;
+}
+
+static inline struct pci_dev *bridge_root_dev(struct pci_dev *dev)
+{
+	while (dev->bus->parent) {
+		/* Move up the chain of bridges. */
+		dev = dev->bus->self;
+	}
+
+	return dev;
+}
+
+/* Do platform specific device initialization at pci_enable_device() time */
+int pcibios_plat_dev_init(struct pci_dev *dev)
 {
 	struct bridge_controller *bc = BRIDGE_CONTROLLER(dev->bus);
-	int irq = bc->pci_int[slot];
+	struct pci_dev *rdev = bridge_root_dev(dev);
+	int slot = PCI_SLOT(rdev->devfn);
+	int irq;
 
+	irq = bc->pci_int[slot];
 	if (irq == -1) {
-		irq = bc->pci_int[slot] = request_bridge_irq(bc);
+		irq = request_bridge_irq(bc);
 		if (irq < 0)
-			panic("Can't allocate interrupt for PCI device %s\n",
-			      pci_name(dev));
+			return irq;
+
+		bc->pci_int[slot] = irq;
 	}
 
 	irq_to_bridge[irq] = bc;
 	irq_to_slot[irq] = slot;
 
-	return irq;
-}
+	dev->irq = irq;
 
-/* Do platform specific device initialization at pci_enable_device() time */
-int pcibios_plat_dev_init(struct pci_dev *dev)
-{
 	return 0;
 }