of/address: Add of_property_read_reg() helper

Add a helper, of_property_read_reg(), to read "reg" entries untranslated
address and size. This function is intended mainly for cases with an
untranslatable "reg" address (i.e. not MMIO). There's also a few
translatable cases such as address cells containing a bus chip-select
number.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

drivers/of/address.c

···
 }
 EXPORT_SYMBOL(__of_get_address);
 
+/**
+ * of_property_read_reg - Retrieve the specified "reg" entry index without translating
+ * @np: device tree node for which to retrieve "reg" from
+ * @idx: "reg" entry index to read
+ * @addr: return value for the untranslated address
+ * @size: return value for the entry size
+ *
+ * Returns -EINVAL if "reg" is not found. Returns 0 on success with addr and
+ * size values filled in.
+ */
+int of_property_read_reg(struct device_node *np, int idx, u64 *addr, u64 *size)
+{
+	const __be32 *prop = of_get_address(np, idx, size, NULL);
+
+	if (!prop)
+		return -EINVAL;
+
+	*addr = of_read_number(prop, of_n_addr_cells(np));
+
+	return 0;
+}
+EXPORT_SYMBOL(of_property_read_reg);
+
 static int parser_init(struct of_pci_range_parser *parser,
 			struct device_node *node, const char *name)
 {

drivers/of/unittest.c

···
 	of_node_put(np);
 }
 
+static void __init of_unittest_reg(void)
+{
+	struct device_node *np;
+	int ret;
+	u64 addr, size;
+
+	np = of_find_node_by_path("/testcase-data/address-tests/bus@80000000/device@1000");
+	if (!np) {
+		pr_err("missing testcase data\n");
+		return;
+	}
+
+	ret = of_property_read_reg(np, 0, &addr, &size);
+	unittest(!ret, "of_property_read_reg(%pOF) returned error %d\n",
+		np, ret);
+	unittest(addr == 0x1000, "of_property_read_reg(%pOF) untranslated address (%llx) incorrect\n",
+		np, addr);
+
+	of_node_put(np);
+}
+
 static void __init of_unittest_parse_interrupts(void)
 {
 	struct device_node *np;
···
 	of_unittest_pci_dma_ranges();
 	of_unittest_bus_ranges();
 	of_unittest_bus_3cell_ranges();
+	of_unittest_reg();
 	of_unittest_match_node();
 	of_unittest_platform_populate();
 	of_unittest_overlay();

include/linux/of_address.h

···
 extern const __be32 *__of_get_address(struct device_node *dev, int index, int bar_no,
 				      u64 *size, unsigned int *flags);
 
+int of_property_read_reg(struct device_node *np, int idx, u64 *addr, u64 *size);
+
 extern int of_pci_range_parser_init(struct of_pci_range_parser *parser,
 			struct device_node *node);
 extern int of_pci_dma_range_parser_init(struct of_pci_range_parser *parser,
···
 					     u64 *size, unsigned int *flags)
 {
 	return NULL;
+}
+
+static inline int of_property_read_reg(struct device_node *np, int idx, u64 *addr, u64 *size)
+{
+	return -ENOSYS;
 }
 
 static inline int of_pci_range_parser_init(struct of_pci_range_parser *parser,