board_f: Add support for CONFIG_OF_BOARD_FIXUP for XIP images

When U-Boot is running from flash memory (execute in place) then
gd->fdt_blob before relocation points to read-only flash memory.

So U-Boot calls board_fix_fdt() with read-only gd->fdt_blob pointer which
cause immediate CPU crash when callback is trying to modify gd->fdt_blob.

Fix this issue by introducing a new config option OF_INITIAL_DTB_READONLY
which moves fix_fdt callback after the reloc_fdt callback. This makes
CONFIG_OF_BOARD_FIXUP working also if U-Boot before relocation is not
running from read/write (S)RAM memory.

This is required for mpc85xx boards when booting from flash NOR.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Mojík <marek.mojik@nic.cz>
Reviewed-by: Marek Behún <kabel@kernel.org>

common/board_f.c

@@ -949,7 +949,7 @@ static const init_fnc_t init_sequence_f[] = {
 	 *  - board info struct
 	 */
 	setup_dest_addr,
-#ifdef CONFIG_OF_BOARD_FIXUP
+#if defined(CONFIG_OF_BOARD_FIXUP) && !defined(CONFIG_OF_INITIAL_DTB_READONLY)
 	fix_fdt,
 #endif
 #ifdef CFG_PRAM
@@ -965,6 +965,10 @@ static const init_fnc_t init_sequence_f[] = {
 	reserve_board,
 	reserve_global_data,
 	reserve_fdt,
+#if defined(CONFIG_OF_BOARD_FIXUP) && defined(CONFIG_OF_INITIAL_DTB_READONLY)
+	reloc_fdt,
+	fix_fdt,
+#endif
 	reserve_bootstage,
 	reserve_bloblist,
 	reserve_arch,
@@ -975,7 +979,9 @@ static const init_fnc_t init_sequence_f[] = {
 	setup_bdinfo,
 	display_new_sp,
 	INIT_FUNC_WATCHDOG_RESET
+#if !defined(CONFIG_OF_BOARD_FIXUP) || !defined(CONFIG_OF_INITIAL_DTB_READONLY)
 	reloc_fdt,
+#endif
 	reloc_bootstage,
 	reloc_bloblist,
 	setup_reloc,

dts/Kconfig

@@ -145,6 +145,12 @@ config OF_EMBED
 
 endchoice
 
+config OF_INITIAL_DTB_READONLY
+	bool "Initial DTB for DT control is read-only"
+	help
+	  If initial DTB for DT control is read-only (e.g. points to
+	  memory-mapped flash memory), then set this option.
+
 config OF_BOARD
 	bool "Provided by the board (e.g a previous loader) at runtime"
 	default y if SANDBOX || OF_HAS_PRIOR_STAGE