kbuild: generate u-boot.cfg as a byproduct of include/autoconf.mk

Our build system still parses ad-hoc CONFIG options in header files
and generates include/autoconf.mk so that Makefiles can reference
them.  This gimmick was introduced in the pre-Kconfig days and will
be kept until Kconfig migration is completed.

The include/autoconf.mk is generated like follows:

  [1] Preprocess include/common.h with -DDO_DEPS_ONLY and
      retrieve macros into include/autoconf.mk.tmp
  [2] Reformat include/autoconf.mk.dep into include/autoconf.mk
      with tools/scripts/define2mk.sed script
  [3] Remove include/autoconf.mk.tmp

Here, include/autoconf.mk.tmp is similar to u-boot.cfg, which is
also generated by preprocessing include/config.h with -DDO_DEPS_ONLY.
In other words, there is much overlap among include/autoconf.mk and
u-boot.cfg build rules.

So, the idea is to split the build rule of include/autoconf.mk
into two stages.  The first preprocesses headers into u-boot.cfg.
The second parses the u-boot.cfg into include/autoconf.mk.  The
build rules of u-boot.cfg in Makefile and spl/Makefile will be gone.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

Makefile

@@ -741,8 +741,7 @@ DO_STATIC_RELA =
 endif
 
 # Always append ALL so that arch config.mk's can add custom ones
-ALL-y += u-boot.srec u-boot.bin u-boot.sym System.map u-boot.cfg \
-	binary_size_check
+ALL-y += u-boot.srec u-boot.bin u-boot.sym System.map binary_size_check
 
 ALL-$(CONFIG_ONENAND_U_BOOT) += u-boot-onenand.bin
 ifeq ($(CONFIG_SPL_FSL_PBL),y)
@@ -942,20 +941,6 @@ u-boot.sha1:	u-boot.bin
 u-boot.dis:	u-boot
 		$(OBJDUMP) -d $< > $@
 
-# If .u-boot.cfg.d is still present, then either:
-# a) The previous build used a Makefile that used if_changed rather than
-#    if_changed_dep when building u-boot.cfg, and hence any later builds will
-#    be unaware of the dependencies for u-boot.cfg. In this case, we must
-#    delete u-boot.cfg to force it and .u-boot.cfg.cmd to be rebuilt the
-#    correct way.
-# b) The previous build failed or was interrupted while building u-boot.cfg,
-#    so deleting u-boot.cfg isn't going to cause any additional work.
-ifneq ($(wildcard $(obj)/.u-boot.cfg.d),)
-  unused := $(shell rm -f $(obj)/u-boot.cfg)
-endif
-u-boot.cfg:	include/config.h FORCE
-	$(call if_changed_dep,cpp_cfg)
-
 ifdef CONFIG_TPL
 SPL_PAYLOAD := tpl/u-boot-with-tpl.bin
 else

scripts/Makefile.autoconf

@@ -58,29 +58,44 @@ include/autoconf.mk.dep: include/config.h FORCE
 # same CONFIG macros
 quiet_cmd_autoconf = GEN     $@
       cmd_autoconf = \
-	$(CPP) $(c_flags) $2 -DDO_DEPS_ONLY -dM $(srctree)/include/common.h > $@.tmp && { \
-		sed -n -f $(srctree)/tools/scripts/define2mk.sed $@.tmp |		\
+		sed -n -f $(srctree)/tools/scripts/define2mk.sed $< |			\
 		while read line; do							\
 			if [ -n "${KCONFIG_IGNORE_DUPLICATES}" ] ||			\
 			   ! grep -q "$${line%=*}=" include/config/auto.conf; then	\
 				echo "$$line";						\
 			fi								\
-		done > $@;								\
-		rm $@.tmp;								\
-	} || {										\
-		rm $@.tmp; false;							\
+		done > $@
+
+quiet_cmd_u_boot_cfg = CFG     $@
+      cmd_u_boot_cfg = \
+	$(CPP) $(c_flags) $2 -DDO_DEPS_ONLY -dM $(srctree)/include/common.h > $@.tmp && { \
+		grep 'define CONFIG_' $@.tmp > $@;			\
+		rm $@.tmp;						\
+	} || {								\
+		rm $@.tmp; false;					\
 	}
 
-include/autoconf.mk: include/config.h FORCE
+u-boot.cfg: include/config.h FORCE
+	$(call cmd,u_boot_cfg)
+
+spl/u-boot.cfg: include/config.h FORCE
+	$(Q)mkdir -p $(dir $@)
+	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD)
+
+tpl/u-boot.cfg: include/config.h FORCE
+	$(Q)mkdir -p $(dir $@)
+	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD -DCONFIG_TPL_BUILD)
+
+include/autoconf.mk: u-boot.cfg
 	$(call cmd,autoconf)
 
-spl/include/autoconf.mk: include/config.h FORCE
+spl/include/autoconf.mk: spl/u-boot.cfg
 	$(Q)mkdir -p $(dir $@)
-	$(call cmd,autoconf,-DCONFIG_SPL_BUILD)
+	$(call cmd,autoconf)
 
-tpl/include/autoconf.mk: include/config.h FORCE
+tpl/include/autoconf.mk: tpl/u-boot.cfg
 	$(Q)mkdir -p $(dir $@)
-	$(call cmd,autoconf,-DCONFIG_SPL_BUILD -DCONFIG_TPL_BUILD)
+	$(call cmd,autoconf)
 
 # include/config.h
 # Prior to Kconfig, it was generated by mkconfig. Now it is created here.

scripts/Makefile.spl

@@ -156,7 +156,7 @@ spl/boot.bin: $(obj)/u-boot-spl.bin FORCE
 	$(call if_changed,mkimage)
 endif
 
-ALL-y	+= $(obj)/$(SPL_BIN).bin $(obj)/$(SPL_BIN).cfg
+ALL-y	+= $(obj)/$(SPL_BIN).bin
 
 ifdef CONFIG_SAMSUNG
 ALL-y	+= $(obj)/$(BOARD)-spl.bin
@@ -216,24 +216,6 @@ quiet_cmd_fdtgrep = FDTGREP $@
 $(obj)/$(SPL_BIN).dtb: dts/dt.dtb $(objtree)/tools/fdtgrep FORCE
 	$(call if_changed,fdtgrep)
 
-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 $@ $<
-
-# If .u-boot.cfg.d is still present, then either:
-# a) The previous build used a Makefile that used if_changed rather than
-#    if_changed_dep when building u-boot.cfg, and hence any later builds will
-#    be unaware of the dependencies for u-boot.cfg. In this case, we must
-#    delete u-boot.cfg to force it and .u-boot.cfg.cmd to be rebuilt the
-#    correct way.
-# b) The previous build failed or was interrupted while building u-boot.cfg,
-#    so deleting u-boot.cfg isn't going to cause any additional work.
-ifneq ($(wildcard $(obj)/.$(SPL_BIN).d),)
-  unused := $(shell rm -f $(obj)/$(SPL_BIN).cfg)
-endif
-$(obj)/$(SPL_BIN).cfg:	include/config.h FORCE
-	$(call if_changed_dep,cpp_cfg)
-
 pythonpath = PYTHONPATH=tools
 
 quiet_cmd_dtocc = DTOC C  $@