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, 2 insertions, 2 deletions

diff --git a/arch/arm/cpu/arm926ejs/config.mk b/arch/arm/cpu/arm926ejs/config.mk
index 4d9895f..f27ca15 100644
--- a/arch/arm/cpu/arm926ejs/config.mk
+++ b/arch/arm/cpu/arm926ejs/config.mk
@@ -13,6 +13,6 @@ ifdef CONFIG_SPL_BUILD
 ALL-y	+= $(OBJTREE)/SPL
 endif
 else
-ALL-y	+= $(obj)u-boot.imx
+ALL-y	+= u-boot.imx
 endif
 endif
diff --git a/arch/arm/cpu/arm926ejs/davinci/config.mk b/arch/arm/cpu/arm926ejs/davinci/config.mk
index d5c978b..69e9d5a 100644
--- a/arch/arm/cpu/arm926ejs/davinci/config.mk
+++ b/arch/arm/cpu/arm926ejs/davinci/config.mk
@@ -4,5 +4,5 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 ifndef CONFIG_SPL_BUILD
-ALL-$(CONFIG_SPL_FRAMEWORK)	+= $(obj)u-boot.ais
+ALL-$(CONFIG_SPL_FRAMEWORK)	+= u-boot.ais
 endif