kbuild: change out-of-tree build

This commit changes the working directory
where the build process occurs.

Before this commit, build process occurred under the source
tree for both in-tree and out-of-tree build.

That's why we needed to add $(obj) prefix to all generated
files in makefiles like follows:
  $(obj)u-boot.bin:  $(obj)u-boot

Here, $(obj) is empty for in-tree build, whereas it points
to the output directory for out-of-tree build.

And our old build system changes the current working directory
with "make -C <sub-dir>" syntax when descending into the
sub-directories.

On the other hand, Kbuild uses a different idea
to handle out-of-tree build and directory descending.

The build process of Kbuild always occurs under the output tree.
When "O=dir/to/store/output/files" is given, the build system
changes the current working directory to that directory and
restarts the make.

Kbuild uses "make -f $(srctree)/scripts/Makefile.build obj=<sub-dir>"
syntax for descending into sub-directories.
(We can write it like "make $(obj)=<sub-dir>" with a shorthand.)
This means the current working directory is always the top
of the output directory.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Tested-by: Gerhard Sittig <gsi@denx.de>

2 files changed, 9 insertions, 9 deletions

diff --git a/arch/blackfin/config.mk b/arch/blackfin/config.mk
index 73fa798..c752025 100644
--- a/arch/blackfin/config.mk
+++ b/arch/blackfin/config.mk
@@ -12,7 +12,7 @@ CONFIG_STANDALONE_LOAD_ADDR ?= 0x1000 -m elf32bfin
 ifeq ($(CONFIG_BFIN_CPU),)
 CONFIG_BFIN_CPU := \
 	$(shell awk '$$2 == "CONFIG_BFIN_CPU" { print $$3 }' \
-		$(src)include/configs/$(BOARD).h)
+		$(srctree)/include/configs/$(BOARD).h)
 else
 CONFIG_BFIN_CPU := $(strip $(CONFIG_BFIN_CPU:"%"=%))
 endif
@@ -28,10 +28,10 @@ PLATFORM_RELFLAGS += -ffunction-sections -fdata-sections
 PLATFORM_RELFLAGS += -mcpu=$(CONFIG_BFIN_CPU)
 
 ifneq ($(CONFIG_BFIN_BOOT_MODE),BFIN_BOOT_BYPASS)
-ALL-y += $(obj)u-boot.ldr
+ALL-y += u-boot.ldr
 endif
 ifeq ($(CONFIG_ENV_IS_EMBEDDED_IN_LDR),y)
-CREATE_LDR_ENV = $(obj)tools/envcrc --binary > $(obj)env-ldr.o
+CREATE_LDR_ENV = tools/envcrc --binary > env-ldr.o
 HOSTCFLAGS_NOPED_ADSP := \
 	$(shell $(CPP) -dD - -mcpu=$(CONFIG_BFIN_CPU) </dev/null \
 		| awk '$$2 ~ /ADSP/ { print "-D" $$2 }')
@@ -47,10 +47,10 @@ LDR_FLAGS-$(CONFIG_BFIN_BOOTROM_USES_EVT1) += -J
 
 LDR_FLAGS += --bmode $(subst BFIN_BOOT_,,$(CONFIG_BFIN_BOOT_MODE))
 LDR_FLAGS += --use-vmas
-LDR_FLAGS += --initcode $(obj)$(CPUDIR)/initcode.o
+LDR_FLAGS += --initcode $(CPUDIR)/initcode.o
 ifneq ($(CONFIG_BFIN_BOOT_MODE),BFIN_BOOT_UART)
 LDR_FLAGS-$(CONFIG_ENV_IS_EMBEDDED_IN_LDR) += \
-	--punchit $$(($(CONFIG_ENV_OFFSET))):$$(($(CONFIG_ENV_SIZE))):$(obj)env-ldr.o
+	--punchit $$(($(CONFIG_ENV_OFFSET))):$$(($(CONFIG_ENV_SIZE))):env-ldr.o
 endif
 ifneq (,$(findstring s,$(MAKEFLAGS)))
 LDR_FLAGS += --quiet
diff --git a/arch/blackfin/cpu/Makefile b/arch/blackfin/cpu/Makefile
index a61594a..369dc74 100644
--- a/arch/blackfin/cpu/Makefile
+++ b/arch/blackfin/cpu/Makefile
@@ -25,9 +25,9 @@ extra-y += check_initcode
 
 # make sure our initcode (which goes into LDR) does not
 # have relocs or external references
-$(obj)initcode.o: CFLAGS += -fno-function-sections -fno-data-sections
+$(obj)/initcode.o: CFLAGS += -fno-function-sections -fno-data-sections
 READINIT = env LC_ALL=C $(CROSS_COMPILE)readelf -s $<
-$(obj)check_initcode: $(obj)initcode.o
+$(obj)/check_initcode: $(obj)/initcode.o
 ifneq ($(CONFIG_BFIN_BOOT_MODE),BFIN_BOOT_BYPASS)
 	@if $(READINIT) | grep '\<GLOBAL\>.*\<UND\>' ; then \
 		echo "$< contains external references!" 1>&2 ; \
@@ -35,7 +35,7 @@ ifneq ($(CONFIG_BFIN_BOOT_MODE),BFIN_BOOT_BYPASS)
 	fi
 endif
 
-$(obj)init.lds: init.lds.S
+$(obj)/init.lds: $(src)/init.lds.S
 	$(CPP) $(CPPFLAGS) $(LDPPFLAGS) -ansi -D__ASSEMBLY__ -P $^ -o $@
-$(obj)init.elf: $(obj)init.lds $(obj)init.o $(obj)initcode.o
+$(obj)/init.elf: $(obj)/init.lds $(obj)/init.o $(obj)/initcode.o
 	$(LD) $(LDFLAGS) -T $^ -o $@