PCI: keystone: Fix interrupt-controller-node lookup

commit eac56aa3 upstream.

Fix child-node lookup during initialisation which was using the wrong
OF-helper and ended up searching the whole device tree depth-first
starting at the parent rather than just matching on its children.

To make things worse, the parent pci node could end up being prematurely
freed as of_find_node_by_name() drops a reference to its first argument.
Any matching child interrupt-controller node was also leaked.

Fixes: 0c4ffcfe ("PCI: keystone: Add TI Keystone PCIe driver")
Cc: stable <stable@vger.kernel.org>     # 3.18
Acked-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
[lorenzo.pieralisi@arm.com: updated commit subject]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
[johan: backport to 4.4]
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/pci/host/pci-keystone.c

@@ -179,14 +179,16 @@ static int ks_pcie_get_irq_controller_info(struct keystone_pcie *ks_pcie,
 	}
 
 	/* interrupt controller is in a child node */
-	*np_temp = of_find_node_by_name(np_pcie, controller);
+	*np_temp = of_get_child_by_name(np_pcie, controller);
 	if (!(*np_temp)) {
 		dev_err(dev, "Node for %s is absent\n", controller);
 		goto out;
 	}
 	temp = of_irq_count(*np_temp);
-	if (!temp)
+	if (!temp) {
+		of_node_put(*np_temp);
 		goto out;
+	}
 	if (temp > max_host_irqs)
 		dev_warn(dev, "Too many %s interrupts defined %u\n",
 			(legacy ? "legacy" : "MSI"), temp);
@@ -200,6 +202,9 @@ static int ks_pcie_get_irq_controller_info(struct keystone_pcie *ks_pcie,
 		if (!host_irqs[temp])
 			break;
 	}
+
+	of_node_put(*np_temp);
+
 	if (temp) {
 		*num_irqs = temp;
 		ret = 0;