Makefile: add rules to generate SPL FIT images

Some platforms require more complex U-Boot images than we can easily
generate via the mkimage command line, for instance to load additional
image files.
Introduce a CONFIG_SPL_FIT_SOURCE and CONFIG_SPL_FIT_GENERATOR symbol,
which can either hold an .its source file describing the image layout,
or, in the second case, a generator tool (script) to create such
a source file. This script gets passed the list of device tree files
from the CONFIG_OF_LIST variable.
A platform or board can define either of those in their defconfig file
to allow an easy building of such an image.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>

Kconfig

@@ -241,6 +241,23 @@ config SPL_FIT_IMAGE_POST_PROCESS
 	  injected into the FIT creation (i.e. the blobs would have been pre-
 	  processed before being added to the FIT image).
 
+config SPL_FIT_SOURCE
+	string ".its source file for U-Boot FIT image"
+	depends on SPL_FIT
+	help
+	  Specifies a (platform specific) FIT source file to generate the
+	  U-Boot FIT image. This could specify further image to load and/or
+	  execute.
+
+config SPL_FIT_GENERATOR
+	string ".its file generator script for U-Boot FIT image"
+	depends on SPL_FIT
+	help
+	  Specifies a (platform specific) script file to generate the FIT
+	  source file used to build the U-Boot FIT image file. This gets
+	  passed a list of supported device tree file stub names to
+	  include in the generated image.
+
 endif # FIT
 
 config OF_BOARD_SETUP

Makefile

@@ -833,6 +833,10 @@ quiet_cmd_mkimage = MKIMAGE $@
 cmd_mkimage = $(objtree)/tools/mkimage $(MKIMAGEFLAGS_$(@F)) -d $< $@ \
 	$(if $(KBUILD_VERBOSE:1=), >$(MKIMAGEOUTPUT))
 
+quiet_cmd_mkfitimage = MKIMAGE $@
+cmd_mkfitimage = $(objtree)/tools/mkimage $(MKIMAGEFLAGS_$(@F)) -f $(U_BOOT_ITS) -E $@ \
+	$(if $(KBUILD_VERBOSE:1=), >$(MKIMAGEOUTPUT))
+
 quiet_cmd_cat = CAT     $@
 cmd_cat = cat $(filter-out $(PHONY), $^) > $@
 
@@ -952,6 +956,19 @@ quiet_cmd_cpp_cfg = CFG     $@
 cmd_cpp_cfg = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) -ansi \
 	-DDO_DEPS_ONLY -D__ASSEMBLY__ -x assembler-with-cpp -P -dM -E -o $@ $<
 
+# Boards with more complex image requirments can provide an .its source file
+# or a generator script
+ifneq ($(CONFIG_SPL_FIT_SOURCE),"")
+U_BOOT_ITS = $(subst ",,$(CONFIG_SPL_FIT_SOURCE))
+else
+ifneq ($(CONFIG_SPL_FIT_GENERATOR),"")
+U_BOOT_ITS := u-boot.its
+$(U_BOOT_ITS): FORCE
+	$(srctree)/$(CONFIG_SPL_FIT_GENERATOR) \
+	$(patsubst %,arch/$(ARCH)/dts/%.dtb,$(subst ",,$(CONFIG_OF_LIST))) > $@
+endif
+endif
+
 ifdef CONFIG_SPL_LOAD_FIT
 MKIMAGEFLAGS_u-boot.img = -f auto -A $(ARCH) -T firmware -C none -O u-boot \
 	-a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
@@ -984,6 +1001,9 @@ u-boot-dtb.img u-boot.img u-boot.kwb u-boot.pbl u-boot-ivt.img: \
 		$(if $(CONFIG_SPL_LOAD_FIT),u-boot-nodtb.bin dts/dt.dtb,u-boot.bin) FORCE
 	$(call if_changed,mkimage)
 
+u-boot.itb: u-boot-nodtb.bin dts/dt.dtb $(U_BOOT_ITS) FORCE
+	$(call if_changed,mkfitimage)
+
 u-boot-spl.kwb: u-boot.img spl/u-boot-spl.bin FORCE
 	$(call if_changed,mkimage)