firmware: refactor firmware/Makefile

Clean up the Makefile. Equivalent *.gen.S files are still produced.

 - Use filechk to remove ugly wordsize_deps

 - Get FWNAME, FWSTR, ASM_WORD, ASM_ALIGN, and PROGBITS out of the
   recipe for readability

 - Remove 'mkdir' because filechk takes care of it
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

firmware/Makefile

 # SPDX-License-Identifier: GPL-2.0
-#
-# kbuild file for firmware/
-#
 
-# Create $(fwabs) from $(CONFIG_EXTRA_FIRMWARE_DIR) -- if it doesn't have a
+# Create $(fwdir) from $(CONFIG_EXTRA_FIRMWARE_DIR) -- if it doesn't have a
 # leading /, it's relative to $(srctree).
 fwdir := $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE_DIR))
-fwabs := $(addprefix $(srctree)/,$(filter-out /%,$(fwdir)))$(filter /%,$(fwdir))
-
-fw-external-y := $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE))
-
-quiet_cmd_fwbin = MK_FW   $@
-      cmd_fwbin = FWNAME="$(patsubst firmware/%.gen.S,%,$@)";		     \
-		  FWSTR="$(subst /,_,$(subst .,_,$(subst -,_,$(patsubst	     \
-				firmware/%.gen.S,%,$@))))";		     \
-		  ASM_WORD=$(if $(CONFIG_64BIT),.quad,.long);		     \
-		  ASM_ALIGN=$(if $(CONFIG_64BIT),3,2);			     \
-		  PROGBITS=$(if $(CONFIG_ARM),%,@)progbits;		     \
-		  echo "/* Generated by firmware/Makefile */"		> $@;\
-		  echo "    .section .rodata"				>>$@;\
-		  echo "    .p2align $${ASM_ALIGN}"			>>$@;\
-		  echo "_fw_$${FWSTR}_bin:"				>>$@;\
-		  echo "    .incbin \"$(2)\""				>>$@;\
-		  echo "_fw_end:"					>>$@;\
-		  echo "   .section .rodata.str,\"aMS\",$${PROGBITS},1"	>>$@;\
-		  echo "    .p2align $${ASM_ALIGN}"			>>$@;\
-		  echo "_fw_$${FWSTR}_name:"				>>$@;\
-		  echo "    .string \"$$FWNAME\""			>>$@;\
-		  echo "    .section .builtin_fw,\"a\",$${PROGBITS}"	>>$@;\
-		  echo "    .p2align $${ASM_ALIGN}"			>>$@;\
-		  echo "    $${ASM_WORD} _fw_$${FWSTR}_name"		>>$@;\
-		  echo "    $${ASM_WORD} _fw_$${FWSTR}_bin"		>>$@;\
-		  echo "    $${ASM_WORD} _fw_end - _fw_$${FWSTR}_bin"	>>$@;
-
-# One of these files will change, or come into existence, whenever
-# the configuration changes between 32-bit and 64-bit. The .S files
-# need to change when that happens.
-wordsize_deps := $(wildcard include/config/64bit.h include/config/32bit.h \
-		include/config/ppc32.h include/config/ppc64.h \
-		include/config/superh32.h include/config/superh64.h \
-		include/config/x86_32.h include/config/x86_64.h \
-		firmware/Makefile)
-
-$(patsubst %,$(obj)/%.gen.S, $(fw-external-y)): %: $(wordsize_deps) \
-		include/config/extra/firmware/dir.h
-	$(call cmd,fwbin,$(fwabs)/$(patsubst $(obj)/%.gen.S,%,$@))
+fwdir := $(addprefix $(srctree)/,$(filter-out /%,$(fwdir)))$(filter /%,$(fwdir))
+
+obj-y  := $(addsuffix .gen.o, $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE)))
+
+FWNAME    = $(patsubst $(obj)/%.gen.S,%,$@)
+FWSTR     = $(subst /,_,$(subst .,_,$(subst -,_,$(FWNAME))))
+ASM_WORD  = $(if $(CONFIG_64BIT),.quad,.long)
+ASM_ALIGN = $(if $(CONFIG_64BIT),3,2)
+PROGBITS  = $(if $(CONFIG_ARM),%,@)progbits
+
+filechk_fwbin = { \
+	echo "/* Generated by $(src)/Makefile */"		;\
+	echo "    .section .rodata"				;\
+	echo "    .p2align $(ASM_ALIGN)"			;\
+	echo "_fw_$(FWSTR)_bin:"				;\
+	echo "    .incbin \"$(fwdir)/$(FWNAME)\""		;\
+	echo "_fw_end:"						;\
+	echo "    .section .rodata.str,\"aMS\",$(PROGBITS),1"	;\
+	echo "    .p2align $(ASM_ALIGN)"			;\
+	echo "_fw_$(FWSTR)_name:"				;\
+	echo "    .string \"$(FWNAME)\""			;\
+	echo "    .section .builtin_fw,\"a\",$(PROGBITS)"	;\
+	echo "    .p2align $(ASM_ALIGN)"			;\
+	echo "    $(ASM_WORD) _fw_$(FWSTR)_name"		;\
+	echo "    $(ASM_WORD) _fw_$(FWSTR)_bin"			;\
+	echo "    $(ASM_WORD) _fw_end - _fw_$(FWSTR)_bin"	;\
+}
+
+$(obj)/%.gen.S: FORCE
+	$(call filechk,fwbin)
 
 # The .o files depend on the binaries directly; the .S files don't.
-$(patsubst %,$(obj)/%.gen.o, $(fw-external-y)): $(obj)/%.gen.o: $(fwdir)/%
-
-obj-y				 += $(patsubst %,%.gen.o, $(fw-external-y))
-
-ifeq ($(KBUILD_SRC),)
-# Makefile.build only creates subdirectories for O= builds, but external
-# firmware might live outside the kernel source tree
-_dummy := $(foreach d,$(addprefix $(obj)/,$(dir $(fw-external-y))), $(shell [ -d $(d) ] || mkdir -p $(d)))
-endif
+$(addprefix $(obj)/, $(obj-y)): $(obj)/%.gen.o: $(fwdir)/%
 
 targets := $(patsubst $(obj)/%,%, \
                                 $(shell find $(obj) -name \*.gen.S 2>/dev/null))