Makefile: Add support for device tree compilation

Add rules to compile dts files into dtb files using the device tree
compiler (dtc). A platform can specify the DTS file to compile using
the platform-dtb-y variable. The flattened device tree binary file to be
used for building the final polatform firmware can be specified using
the new FW_PAYLOAD_FDT firmware configuration option to point to the
automatically compiled FDT file. Using the existing FW_PAYLOAD_FDT_PATH
configuration option is still possible and will take precedence over
the FW_PAYLOAD_FDT definition.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

Makefile

@@ -79,6 +79,7 @@ include $(firmware-object-mks)
 lib-objs-path-y=$(foreach obj,$(lib-objs-y),$(build_dir)/lib/$(obj))
 ifdef PLATFORM
 platform-objs-path-y=$(foreach obj,$(platform-objs-y),$(build_dir)/$(platform_subdir)/$(obj))
+platform-dtb-path-y=$(foreach obj,$(platform-dtb-y),$(build_dir)/$(platform_subdir)/$(obj))
 platform-common-objs-path-y=$(foreach obj,$(platform-common-objs-y),$(build_dir)/platform/common/$(obj))
 firmware-bins-path-y=$(foreach bin,$(firmware-bins-y),$(build_dir)/$(platform_subdir)/firmware/$(bin))
 endif
@@ -154,6 +155,9 @@ else
 OBJCOPY		?=	objcopy
 endif
 
+DTC		=	dtc
+DTCFLAGS	=	-O dtb
+
 # Setup functions for compilation
 define dynamic_flags
 -I$(shell dirname $(2)) -D__OBJNAME__=$(subst -,_,$(shell basename $(1) .o))
@@ -212,10 +216,14 @@ compile_ar = $(CMD_PREFIX)mkdir -p `dirname $(1)`; \
 compile_objcopy = $(CMD_PREFIX)mkdir -p `dirname $(1)`; \
 	     echo " OBJCOPY   $(subst $(build_dir)/,,$(1))"; \
 	     $(OBJCOPY) -S -O binary $(2) $(1)
+compile_dts = $(CMD_PREFIX)mkdir -p `dirname $(1)`; \
+	     echo " DTC       $(subst $(build_dir)/,,$(1))"; \
+	     $(DTC) $(DTCFLAGS) -o $(1) $(2)
 
 targets-y  = $(build_dir)/lib/libsbi.a
 ifdef PLATFORM
 targets-y += $(build_dir)/$(platform_subdir)/lib/libplatsbi.a
+targets-y += $(platform-dtb-path-y)
 endif
 targets-y += $(firmware-bins-path-y)
 
@@ -265,6 +273,9 @@ $(build_dir)/$(platform_subdir)/%.dep: $(src_dir)/%.S
 $(build_dir)/$(platform_subdir)/%.o: $(src_dir)/%.S
 	$(call compile_as,$@,$<)
 
+$(build_dir)/%.dtb: $(src_dir)/%.dts
+	$(call compile_dts,$@,$<)
+
 # Rule for "make docs"
 $(build_dir)/docs/latex/refman.pdf: $(build_dir)/docs/latex/refman.tex
 	$(CMD_PREFIX)mkdir -p $(build_dir)/docs

docs/firmware/fw_payload.md

@@ -57,6 +57,14 @@ device tree file is specified by the platform (c.f. *FW_PAYLOAD_FDT*),
 then the firmware will expect the FDT to be passed as an argument by
 the prior booting stage.
 
+* **FW_PAYLOAD_FDT** - Path to an internal flattened device tree
+binary file defined by the platform code. The file name must match the
+DTB file name specified in the platform *objects.mk* file with the
+*platform-dtb-y* entry. This option results in *FW_PAYLOAD_FDT_PATH* to
+be automatically set. Specifying *FW_PAYLOAD_FDT_PATH* on the `make`
+command line disables *FW_PAYLOAD_FDT* and the command line specified
+device tree binary file is used for building the final firmware.
+
 * **FW_PAYLOAD_FDT_ADDR** - Address where the FDT passed by the prior
 booting stage or specified by the *FW_PAYLOAD_FDT_PATH* parameter and
 embedded in the *.text* section will be placed before executing the

firmware/external_deps.mk

@@ -8,3 +8,4 @@
 #
 
 $(build_dir)/$(platform_subdir)/firmware/fw_payload.o: $(FW_PAYLOAD_PATH_FINAL)
+$(build_dir)/$(platform_subdir)/firmware/fw_payload.o: $(FW_PAYLOAD_FDT_PATH)

firmware/objects.mk

@@ -39,6 +39,11 @@ ifdef FW_PAYLOAD_ALIGN
 firmware-genflags-$(FW_PAYLOAD) += -DFW_PAYLOAD_ALIGN=$(FW_PAYLOAD_ALIGN)
 endif
 
+ifndef FW_PAYLOAD_FDT_PATH
+ifdef FW_PAYLOAD_FDT
+FW_PAYLOAD_FDT_PATH=$(build_dir)/$(platform_subdir)/$(FW_PAYLOAD_FDT)
+endif
+endif
 ifdef FW_PAYLOAD_FDT_PATH
 firmware-genflags-$(FW_PAYLOAD) += -DFW_PAYLOAD_FDT_PATH=$(FW_PAYLOAD_FDT_PATH)
 endif