ACPI/IORT: Look up IORT node through struct fwnode_handle pointer

Current IORT code provides a function (ie iort_get_fwnode())
which looks up a struct fwnode_handle pointer through a
struct acpi_iort_node pointer for SMMU components but it
lacks a function that implements the reverse look-up, namely
struct fwnode_handle* -> struct acpi_iort_node*.

Devices that are not IORT named components cannot be retrieved through
their associated IORT named component scan interface because they just
are not represented in the ACPI namespace; the reverse look-up is
therefore required for all platform devices that represent IORT nodes
(eg SMMUs) so that the struct acpi_iort_node* can be retrieved from the
struct device->fwnode pointer.
Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
[lorenzo.pieralisi@arm.com: re-indented/rewrote the commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

drivers/acpi/arm64/iort.c

@@ -126,6 +126,31 @@ static inline void iort_delete_fwnode(struct acpi_iort_node *node)
 	spin_unlock(&iort_fwnode_lock);
 }
 
+/**
+ * iort_get_iort_node() - Retrieve iort_node associated with an fwnode
+ *
+ * @fwnode: fwnode associated with device to be looked-up
+ *
+ * Returns: iort_node pointer on success, NULL on failure
+ */
+static inline struct acpi_iort_node *iort_get_iort_node(
+			struct fwnode_handle *fwnode)
+{
+	struct iort_fwnode *curr;
+	struct acpi_iort_node *iort_node = NULL;
+
+	spin_lock(&iort_fwnode_lock);
+	list_for_each_entry(curr, &iort_fwnode_list, list) {
+		if (curr->fwnode == fwnode) {
+			iort_node = curr->iort_node;
+			break;
+		}
+	}
+	spin_unlock(&iort_fwnode_lock);
+
+	return iort_node;
+}
+
 typedef acpi_status (*iort_find_node_callback)
 	(struct acpi_iort_node *node, void *context);
 
@@ -422,9 +447,25 @@ static struct acpi_iort_node *iort_find_dev_node(struct device *dev)
 {
 	struct pci_bus *pbus;
 
-	if (!dev_is_pci(dev))
+	if (!dev_is_pci(dev)) {
+		struct acpi_iort_node *node;
+		/*
+		 * scan iort_fwnode_list to see if it's an iort platform
+		 * device (such as SMMU, PMCG),its iort node already cached
+		 * and associated with fwnode when iort platform devices
+		 * were initialized.
+		 */
+		node = iort_get_iort_node(dev->fwnode);
+		if (node)
+			return node;
+
+		/*
+		 * if not, then it should be a platform device defined in
+		 * DSDT/SSDT (with Named Component node in IORT)
+		 */
 		return iort_scan_node(ACPI_IORT_NODE_NAMED_COMPONENT,
 				      iort_match_node_callback, dev);
+	}
 
 	/* Find a PCI root bus */
 	pbus = to_pci_dev(dev)->bus;