kbuild: consolidate Devicetree dtb build rules

There is nothing arch specific about building dtb files other than their
location under /arch/*/boot/dts/. Keeping each arch aligned is a pain.
The dependencies and supported targets are all slightly different.
Also, a cross-compiler for each arch is needed, but really the host
compiler preprocessor is perfectly fine for building dtbs. Move the
build rules to a common location and remove the arch specific ones. This
is done in a single step to avoid warnings about overriding rules.

The build dependencies had been a mixture of 'scripts' and/or 'prepare'.
These pull in several dependencies some of which need a target compiler
(specifically devicetable-offsets.h) and aren't needed to build dtbs.
All that is really needed is dtc, so adjust the dependencies to only be
dtc.

This change enables support 'dtbs_install' on some arches which were
missing the target.

Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Paul Burton <paul.burton@mips.com>
Acked-by: Ley Foon Tan <ley.foon.tan@intel.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-kbuild@vger.kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-mips@linux-mips.org
Cc: nios2-dev@lists.rocketboards.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-xtensa@linux-xtensa.org
Signed-off-by: Rob Herring <robh@kernel.org>

Makefile

@@ -1071,7 +1071,7 @@ include/config/kernel.release: $(srctree)/Makefile FORCE
 # Carefully list dependencies so we do not try to build scripts twice
 # in parallel
 PHONY += scripts
-scripts: scripts_basic asm-generic gcc-plugins $(autoksyms_h)
+scripts: scripts_basic scripts_dtc asm-generic gcc-plugins $(autoksyms_h)
 	$(Q)$(MAKE) $(build)=$(@)
 
 # Things we need to do before we recursively start building the kernel
@@ -1215,6 +1215,35 @@ kselftest-merge:
 		$(srctree)/tools/testing/selftests/*/config
 	+$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
 
+# ---------------------------------------------------------------------------
+# Devicetree files
+
+ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
+dtstree := arch/$(SRCARCH)/boot/dts
+endif
+
+ifneq ($(dtstree),)
+
+%.dtb: prepare3 scripts_dtc
+	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
+
+PHONY += dtbs dtbs_install
+dtbs: prepare3 scripts_dtc
+	$(Q)$(MAKE) $(build)=$(dtstree)
+
+dtbs_install:
+	$(Q)$(MAKE) $(dtbinst)=$(dtstree)
+
+ifdef CONFIG_OF_EARLY_FLATTREE
+all: dtbs
+endif
+
+endif
+
+PHONY += scripts_dtc
+scripts_dtc: scripts_basic
+	$(Q)$(MAKE) $(build)=scripts/dtc
+
 # ---------------------------------------------------------------------------
 # Modules
 
@@ -1424,6 +1453,12 @@ help:
 	@echo  '  kselftest-merge - Merge all the config dependencies of kselftest to existing'
 	@echo  '                    .config.'
 	@echo  ''
+	@$(if $(dtstree), \
+		echo 'Devicetree:'; \
+		echo '* dtbs            - Build device tree blobs for enabled boards'; \
+		echo '  dtbs_install    - Install dtbs to $(INSTALL_DTBS_PATH)'; \
+		echo '')
+
 	@echo 'Userspace tools targets:'
 	@echo '  use "make tools/help"'
 	@echo '  or  "cd tools; make help"'

arch/arc/Makefile

@@ -132,11 +132,5 @@ boot_targets += uImage uImage.bin uImage.gz
 $(boot_targets): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
 
-%.dtb %.dtb.S %.dtb.o: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
-
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)

arch/arm/Makefile

@@ -307,12 +307,7 @@ else
 KBUILD_IMAGE := $(boot)/zImage
 endif
 
-# Build the DT binary blobs if we have OF configured
-ifeq ($(CONFIG_USE_OF),y)
-KBUILD_DTBS := dtbs
-endif
-
-all:	$(notdir $(KBUILD_IMAGE)) $(KBUILD_DTBS)
+all:	$(notdir $(KBUILD_IMAGE))
 
 
 archheaders:
@@ -339,17 +334,6 @@ $(BOOT_TARGETS): vmlinux
 $(INSTALL_TARGETS):
 	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $@
 
-%.dtb: | scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
-
-PHONY += dtbs dtbs_install
-
-dtbs: prepare scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
-dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=$(boot)/dts
-
 PHONY += vdso_install
 vdso_install:
 ifeq ($(CONFIG_VDSO),y)
@@ -371,8 +355,6 @@ define archhelp
   echo  '  uImage        - U-Boot wrapped zImage'
   echo  '  bootpImage    - Combined zImage and initial RAM disk'
   echo  '                  (supply initrd image via make variable INITRD=<path>)'
-  echo  '* dtbs          - Build device tree blobs for enabled boards'
-  echo  '  dtbs_install  - Install dtbs to $(INSTALL_DTBS_PATH)'
   echo  '  install       - Install uncompressed kernel'
   echo  '  zinstall      - Install compressed kernel'
   echo  '  uinstall      - Install U-Boot wrapped compressed kernel'

arch/arm64/Makefile

@@ -113,9 +113,8 @@ core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
 # Default target when executing plain make
 boot		:= arch/arm64/boot
 KBUILD_IMAGE	:= $(boot)/Image.gz
-KBUILD_DTBS	:= dtbs
 
-all:	Image.gz $(KBUILD_DTBS)
+all:	Image.gz
 
 
 Image: vmlinux
@@ -127,17 +126,6 @@ Image.%: Image
 zinstall install:
 	$(Q)$(MAKE) $(build)=$(boot) $@
 
-%.dtb: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
-
-PHONY += dtbs dtbs_install
-
-dtbs: prepare scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
-dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=$(boot)/dts
-
 PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso $@
@@ -145,7 +133,6 @@ vdso_install:
 # We use MRPROPER_FILES and CLEAN_FILES now
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
-	$(Q)$(MAKE) $(clean)=$(boot)/dts
 
 # We need to generate vdso-offsets.h before compiling certain files in kernel/.
 # In order to do that, we should use the archprepare target, but we can't since
@@ -160,8 +147,6 @@ vdso_prepare: prepare0
 define archhelp
   echo  '* Image.gz      - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)'
   echo  '  Image         - Uncompressed kernel image (arch/$(ARCH)/boot/Image)'
-  echo  '* dtbs          - Build device tree blobs for enabled boards'
-  echo  '  dtbs_install  - Install dtbs to $(INSTALL_DTBS_PATH)'
   echo  '  install       - Install uncompressed kernel'
   echo  '  zinstall      - Install compressed kernel'
   echo  '                  Install using (your) ~/bin/installkernel or'

arch/c6x/Makefile

@@ -40,9 +40,7 @@ boot := arch/$(ARCH)/boot
 DTB:=$(subst dtbImage.,,$(filter dtbImage.%, $(MAKECMDGOALS)))
 export DTB
 
-ifneq ($(DTB),)
 core-y	+= $(boot)/dts/
-endif
 
 # With make 3.82 we cannot mix normal and wildcard targets
 

arch/h8300/Makefile

@@ -31,21 +31,12 @@ CROSS_COMPILE := h8300-unknown-linux-
 endif
 
 core-y	+= arch/$(ARCH)/kernel/ arch/$(ARCH)/mm/
-ifneq '$(CONFIG_H8300_BUILTIN_DTB)' '""'
-core-y += arch/h8300/boot/dts/
-endif
+core-y	+= arch/$(ARCH)/boot/dts/
 
 libs-y	+= arch/$(ARCH)/lib/
 
 boot := arch/h8300/boot
 
-%.dtb %.dtb.S %.dtb.o: | scripts
-	$(Q)$(MAKE) $(build)=arch/h8300/boot/dts arch/h8300/boot/dts/$@
-
-PHONY += dtbs
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=arch/h8300/boot/dts
-
 archmrproper:
 
 archclean:

arch/microblaze/Makefile

@@ -65,9 +65,7 @@ boot := arch/microblaze/boot
 # Are we making a simpleImage.<boardname> target? If so, crack out the boardname
 DTB:=$(subst simpleImage.,,$(filter simpleImage.%, $(MAKECMDGOALS)))
 
-ifneq ($(DTB),)
-	core-y	+= $(boot)/dts/
-endif
+core-y	+= $(boot)/dts/
 
 # defines filename extension depending memory management type
 ifeq ($(CONFIG_MMU),)

arch/microblaze/boot/dts/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 
+ifneq ($(DTB),)
 obj-y += linked_dtb.o
 
 # Ensure system.dtb exists
@@ -11,6 +12,7 @@ ifneq ($(DTB),system)
 $(obj)/system.dtb: $(obj)/$(DTB).dtb
 	$(call if_changed,cp)
 endif
+endif
 
 quiet_cmd_cp = CP      $< $@$2
 	cmd_cp = cat $< >$@$2 || (rm -f $@ && echo false)

arch/mips/Makefile

@@ -407,18 +407,7 @@ endif
 CLEAN_FILES += vmlinux.32 vmlinux.64
 
 # device-trees
-core-$(CONFIG_BUILTIN_DTB) += arch/mips/boot/dts/
-
-%.dtb %.dtb.S %.dtb.o: | scripts
-	$(Q)$(MAKE) $(build)=arch/mips/boot/dts arch/mips/boot/dts/$@
-
-PHONY += dtbs
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=arch/mips/boot/dts
-
-PHONY += dtbs_install
-dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=arch/mips/boot/dts
+core-y += arch/mips/boot/dts/
 
 archprepare:
 ifdef CONFIG_MIPS32_N32
@@ -461,8 +450,6 @@ define archhelp
 	echo '  uImage.lzma          - U-Boot image (lzma)'
 	echo '  uImage.lzo           - U-Boot image (lzo)'
 	echo '  uzImage.bin          - U-Boot image (self-extracting)'
-	echo '  dtbs                 - Device-tree blobs for enabled boards'
-	echo '  dtbs_install         - Install dtbs to $(INSTALL_DTBS_PATH)'
 	echo
 	echo '  These will be default as appropriate for a configured platform.'
 	echo

arch/nds32/Makefile

@@ -43,7 +43,7 @@ CHECKFLAGS      += -D__NDS32_EB__
 endif
 
 boot := arch/nds32/boot
-core-$(BUILTIN_DTB) += $(boot)/dts/
+core-y += $(boot)/dts/
 
 .PHONY: FORCE
 

arch/nios2/Makefile

@@ -56,12 +56,6 @@ all: vmImage
 archclean:
 	$(Q)$(MAKE) $(clean)=$(nios2-boot)
 
-%.dtb %.dtb.S %.dtb.o: | scripts
-	$(Q)$(MAKE) $(build)=$(nios2-boot)/dts $(nios2-boot)/dts/$@
-
-dtbs:
-	$(Q)$(MAKE) $(build)=$(nios2-boot)/dts
-
 $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(nios2-boot) $(nios2-boot)/$@
 
@@ -74,5 +68,4 @@ define archhelp
   echo  '                     (your) ~/bin/$(INSTALLKERNEL) or'
   echo  '                     (distribution) /sbin/$(INSTALLKERNEL) or'
   echo  '                     install to $$(INSTALL_PATH)'
-  echo  '  dtbs            - Build device tree blobs for enabled boards'
 endef

arch/nios2/boot/Makefile

@@ -31,9 +31,5 @@ $(obj)/zImage: $(obj)/compressed/vmlinux FORCE
 $(obj)/compressed/vmlinux: $(obj)/vmlinux.gz FORCE
 	$(Q)$(MAKE) $(build)=$(obj)/compressed $@
 
-targets += $(dtb-y)
-
-$(obj)/dtbs: $(addprefix $(obj)/, $(dtb-y))
-
 install:
 	sh $(srctree)/$(src)/install.sh $(KERNELRELEASE) $(BOOTIMAGE) System.map "$(INSTALL_PATH)"

arch/powerpc/Makefile

@@ -293,9 +293,6 @@ $(BOOT_TARGETS2): vmlinux
 bootwrapper_install:
 	$(Q)$(MAKE) $(build)=$(boot) $(patsubst %,$(boot)/%,$@)
 
-%.dtb: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(patsubst %,$(boot)/dts/%,$@)
-
 # Used to create 'merged defconfigs'
 # To use it $(call) it with the first argument as the base defconfig
 # and the second argument as a space separated list of .config files to merge,

arch/xtensa/Makefile

@@ -84,28 +84,18 @@ LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 head-y		:= arch/xtensa/kernel/head.o
 core-y		+= arch/xtensa/kernel/ arch/xtensa/mm/
 core-y		+= $(buildvar) $(buildplf)
+core-y 		+= arch/xtensa/boot/dts/
 
 libs-y		+= arch/xtensa/lib/ $(LIBGCC)
 drivers-$(CONFIG_OPROFILE)	+= arch/xtensa/oprofile/
 
-ifneq ($(CONFIG_BUILTIN_DTB),"")
-core-$(CONFIG_OF) += arch/xtensa/boot/dts/
-endif
-
 boot		:= arch/xtensa/boot
 
 all Image zImage uImage: vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $@
 
-%.dtb:
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
-
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
 define archhelp
   @echo '* Image       - Kernel ELF image with reset vector'
   @echo '* zImage      - Compressed kernel image (arch/xtensa/boot/images/zImage.*)'
   @echo '* uImage      - U-Boot wrapped image'
-  @echo '  dtbs        - Build device tree blobs for enabled boards'
 endef

scripts/Makefile

@@ -39,8 +39,7 @@ build_unifdef: $(obj)/unifdef
 subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-y                     += mod
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
-subdir-$(CONFIG_DTC)         += dtc
 subdir-$(CONFIG_GDB_SCRIPTS) += gdb
 
 # Let clean descend into subdirs
-subdir-	+= basic kconfig package gcc-plugins
+subdir-	+= basic dtc kconfig package gcc-plugins

scripts/Makefile.lib

@@ -283,7 +283,7 @@ $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
 
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
-	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
+	$(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
 	$(DTC) -O dtb -o $@ -b 0 \
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \

scripts/dtc/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # scripts/dtc makefile
 
-hostprogs-y	:= dtc
+hostprogs-$(CONFIG_DTC) := dtc
 always		:= $(hostprogs-y)
 
 dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \