of/fdt: Add endianness helper function for early init code

Provide a libfdt-based equivalent for of_device_is_big_endian(), suitable
for use in the early_init_* functions.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/fdt.c

@@ -108,6 +108,25 @@ int of_fdt_is_compatible(const void *blob,
 	return 0;
 }
 
+/**
+ * of_fdt_is_big_endian - Return true if given node needs BE MMIO accesses
+ * @blob: A device tree blob
+ * @node: node to test
+ *
+ * Returns true if the node has a "big-endian" property, or if the kernel
+ * was compiled for BE *and* the node has a "native-endian" property.
+ * Returns false otherwise.
+ */
+bool of_fdt_is_big_endian(const void *blob, unsigned long node)
+{
+	if (fdt_getprop(blob, node, "big-endian", NULL))
+		return true;
+	if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) &&
+	    fdt_getprop(blob, node, "native-endian", NULL))
+		return true;
+	return false;
+}
+
 /**
  * of_fdt_match - Return true if node matches a list of compatible values
  */

include/linux/of_fdt.h

@@ -33,6 +33,8 @@ extern void *of_fdt_get_property(const void *blob,
 extern int of_fdt_is_compatible(const void *blob,
 				unsigned long node,
 				const char *compat);
+extern bool of_fdt_is_big_endian(const void *blob,
+				 unsigned long node);
 extern int of_fdt_match(const void *blob, unsigned long node,
 			const char *const *compat);
 extern void of_fdt_unflatten_tree(unsigned long *blob,