fdt_support.c: Allow late kernel cmdline modification

By declaring board-specific board_fdt_chosen_bootargs() the kernel
command line arguments can be adjusted before injecting to flat dt
chosen node.

Signed-off-by: Niko Mauno <niko.mauno@vaisala.com>

common/fdt_support.c

@@ -269,6 +269,15 @@ int fdt_initrd(void *fdt, ulong initrd_start, ulong initrd_end)
 	return 0;
 }
 
+/**
+ * board_fdt_chosen_bootargs - boards may override this function to use
+ *                             alternative kernel command line arguments
+ */
+__weak char *board_fdt_chosen_bootargs(void)
+{
+	return env_get("bootargs");
+}
+
 int fdt_chosen(void *fdt)
 {
 	int   nodeoffset;
@@ -286,7 +295,8 @@ int fdt_chosen(void *fdt)
 	if (nodeoffset < 0)
 		return nodeoffset;
 
-	str = env_get("bootargs");
+	str = board_fdt_chosen_bootargs();
+
 	if (str) {
 		err = fdt_setprop(fdt, nodeoffset, "bootargs", str,
 				  strlen(str) + 1);

include/fdt_support.h

@@ -185,6 +185,16 @@ int fdt_find_or_add_subnode(void *fdt, int parentoffset, const char *name);
  */
 int ft_board_setup(void *blob, struct bd_info *bd);
 
+/**
+ * board_fdt_chosen_bootargs() - Arbitrarily amend fdt kernel command line
+ *
+ * This is used for late modification of kernel command line arguments just
+ * before they are added into the /chosen node in flat device tree.
+ *
+ * @return: pointer to kernel command line arguments in memory
+ */
+char *board_fdt_chosen_bootargs(void);
+
 /*
  * The keystone2 SOC requires all 32 bit aliased addresses to be converted
  * to their 36 physical format. This has to happen after all fdt nodes