[PATCH] arc: dts - remove default value if CONFIG_ARC_BUILTIN_DTB_NAME is blank

[Alexey Brodkin <Alexey.Brodkin@synopsys.com>]

As of today default .dtb will be built (and subsequently will be built-in
kernel binary) even if CONFIG_ARC_BUILTIN_DTB_NAME is not set.

But it is possible we're going to use external .dtb and so we don't want to
have .dtb built-in kernel binary.

For example that could be the case with:
 a) U-Boot which loads .dtb in DDR and passes its address to the kernel
 b) OpenWRT which embeds .dtb in existing kernel binary

This change excludes .dtb building if CONFIG_ARC_BUILTIN_DTB_NAME is
blank.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
---
 arch/arc/Makefile          | 2 ++
 arch/arc/boot/dts/Makefile | 6 ++----
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arc/Makefile b/arch/arc/Makefile
index 8a27a48..b0cb6de 100644
--- a/arch/arc/Makefile
+++ b/arch/arc/Makefile
@@ -94,7 +94,9 @@ head-y		:= arch/arc/kernel/head.o
 core-y		+= arch/arc/
 
 # w/o this dtb won't embed into kernel binary
+ifneq ($(CONFIG_ARC_BUILTIN_DTB_NAME),"")
 core-y		+= arch/arc/boot/dts/
+endif
 
 core-$(CONFIG_ARC_PLAT_SIM)	+= arch/arc/plat-sim/
 core-$(CONFIG_ARC_PLAT_TB10X)	+= arch/arc/plat-tb10x/
diff --git a/arch/arc/boot/dts/Makefile b/arch/arc/boot/dts/Makefile
index b0e3f19..4dcab5b 100644
--- a/arch/arc/boot/dts/Makefile
+++ b/arch/arc/boot/dts/Makefile
@@ -1,13 +1,11 @@
 # Built-in dtb
-builtindtb-y		:= nsim_700
 
 ifneq ($(CONFIG_ARC_BUILTIN_DTB_NAME),"")
 	builtindtb-y	:= $(patsubst "%",%,$(CONFIG_ARC_BUILTIN_DTB_NAME))
+	obj-y   += $(builtindtb-y).dtb.o
+	targets += $(builtindtb-y).dtb
 endif
 
-obj-y   += $(builtindtb-y).dtb.o
-targets += $(builtindtb-y).dtb
-
 .SECONDARY: $(obj)/$(builtindtb-y).dtb.S
 
 dtbs:  $(addprefix  $(obj)/, $(builtindtb-y).dtb)
-- 
2.4.3