dts: re-write dts/Makefile more simply with Kbuild

Useful rules in scripts/Makefile.lib allows us to easily
generate a device tree blob and wrap it in assembly code.

We do not need to parse a linker script to get output format and arch.

This commit deletes ./u-boot.dtb since it is a copy of dts/dt.dtb.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

dts/.gitignore

@@ -0,0 +1,2 @@
+*.dtb
+*.dtb.S

dts/Makefile

@@ -7,64 +7,32 @@
 # This Makefile builds the internal U-Boot fdt if CONFIG_OF_CONTROL is
 # enabled. See doc/README.fdt-control for more details.
 
-DTS_INCDIRS =  $(SRCTREE)/board/$(VENDOR)/$(BOARD)/dts
-DTS_INCDIRS += $(SRCTREE)/board/$(VENDOR)/dts
-DTS_INCDIRS += $(SRCTREE)/arch/$(ARCH)/dts
-
-DTS_CPPFLAGS := -x assembler-with-cpp -undef -D__DTS__ \
-		-nostdinc $(addprefix -I,$(DTS_INCDIRS))
-
-DTC_FLAGS := -R 4 -p 0x1000 \
-	$(addprefix -i ,$(DTS_INCDIRS))
-
-# Use a constant name for this so we can access it from C code.
-# objcopy doesn't seem to allow us to set the symbol name independently of
-# the filename.
-DT_BIN	:= $(obj)/dt.dtb
-
 DEVICE_TREE ?= $(CONFIG_DEFAULT_DEVICE_TREE:"%"=%)
 ifeq ($(DEVICE_TREE),)
-$(DT_BIN): FORCE
-	echo >&2 "Please define CONFIG_DEFAULT_DEVICE_TREE in your board header file"
-else
-$(DT_BIN): $(TOPDIR)/board/$(VENDOR)/dts/$(DEVICE_TREE).dts
-	$(CPP) $(DTS_CPPFLAGS) $< -o $(DT_BIN).dts.tmp
-	$(DTC) $(DTC_FLAGS) -O dtb -o ${DT_BIN} $(DT_BIN).dts.tmp
+DEVICE_TREE := notfound
 endif
 
-process_lds = \
-	$(1) | sed -r -n 's/^OUTPUT_$(2)[ ("]*([^")]*).*/\1/p'
+DTS := $(srctree)/board/$(VENDOR)/dts/$(DEVICE_TREE).dts
 
-# Run the compiler and get the link script from the linker
-GET_LDS = $(CC) $(c_flags) $(ld_flags) -Wl,--verbose 2>&1
+DTC_FLAGS += -i $(srctree)/arch/$(ARCH)/dts -R 4 -p 0x1000
 
-$(obj)/dt.o: $(DT_BIN)
-	# We want the output format and arch.
-	# We also hope to win a prize for ugliest Makefile / shell interaction
-	# We look in the LDSCRIPT first.
-	# Then try the linker which should give us the answer.
-	# Then check it worked.
-	[ -n "$(LDSCRIPT)" ] && \
-		oformat=`$(call process_lds,cat $(LDSCRIPT),FORMAT)` && \
-		oarch=`$(call process_lds,cat $(LDSCRIPT),ARCH)` ;\
-	\
-	[ -z $${oformat} ] && \
-		oformat=`$(call process_lds,$(GET_LDS),FORMAT)` ;\
-	[ -z $${oarch} ] && \
-		oarch=`$(call process_lds,$(GET_LDS),ARCH)` ;\
-	\
-	[ -z $${oformat} ] && \
-		echo "Cannot read OUTPUT_FORMAT from lds file $(LDSCRIPT)" && \
-		exit 1 || true ;\
-	[ -z $${oarch} ] && \
-		echo "Cannot read OUTPUT_ARCH from lds file $(LDSCRIPT)" && \
-		exit 1 || true ;\
-	\
-	cd $(dir ${DT_BIN}) && \
-	$(OBJCOPY) -I binary -O $${oformat} -B $${oarch} \
-		$(notdir ${DT_BIN}) $(notdir $@)
-	rm $(DT_BIN)
+$(obj)/dt.dtb: $(DTS) FORCE
+	$(call if_changed_dep,dtc)
 
-obj-$(CONFIG_OF_EMBED)	:= dt.o
+targets += dt.dtb
 
-binary:	$(DT_BIN)
+$(DTS):
+	@echo >&2
+	@echo >&2 "Device Tree Source is not specified."
+	@echo >&2 "Please define 'CONFIG_DEFAULT_DEVICE_TREE'"
+	@echo >&2 "or build with 'DEVICE_TREE=<dts-file-name>' argument"
+	@/bin/false
+
+.SECONDARY: $(obj)/dt.dtb.S
+
+obj-$(CONFIG_OF_EMBED) := dt.dtb.o
+
+dtbs: $(obj)/dt.dtb
+	@:
+
+clean-files := dt.dtb.S