arm64: Add architectural support for PCI

Use the generic PCI domain and OF functions to provide support for PCI
on arm64.

[bhelgaas: Change comments to use generic PCI, not just PCIe.  Nothing at
this level is PCIe-specific.]
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/pci.c

@@ -0,0 +1,70 @@
+/*
+ * Code borrowed from powerpc/kernel/pci-common.c
+ *
+ * Copyright (C) 2003 Anton Blanchard <anton@au.ibm.com>, IBM
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/of_pci.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+
+#include <asm/pci-bridge.h>
+
+/*
+ * Called after each bus is probed, but before its children are examined
+ */
+void pcibios_fixup_bus(struct pci_bus *bus)
+{
+	/* nothing to do, expected to be removed in the future */
+}
+
+/*
+ * We don't have to worry about legacy ISA devices, so nothing to do here
+ */
+resource_size_t pcibios_align_resource(void *data, const struct resource *res,
+				resource_size_t size, resource_size_t align)
+{
+	return res->start;
+}
+
+/*
+ * Try to assign the IRQ number from DT when adding a new device
+ */
+int pcibios_add_device(struct pci_dev *dev)
+{
+	dev->irq = of_irq_parse_and_map_pci(dev, 0, 0);
+
+	return 0;
+}
+
+
+#ifdef CONFIG_PCI_DOMAINS_GENERIC
+static bool dt_domain_found = false;
+
+void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
+{
+	int domain = of_get_pci_domain_nr(parent->of_node);
+
+	if (domain >= 0) {
+		dt_domain_found = true;
+	} else if (dt_domain_found == true) {
+		dev_err(parent, "Node %s is missing \"linux,pci-domain\" property in DT\n",
+			parent->of_node->full_name);
+		return;
+	} else {
+		domain = pci_get_new_domain_nr();
+	}
+
+	bus->domain_nr = domain;
+}
+#endif