ARC: [kbuild] Avoid DTB rebuilds if DTS are untouched
Currently, for every ARC kernel build I see the following:
--------------->8-----------------
DTB arch/arc/boot/dts/angel4.dtb.S
AS arch/arc/boot/dts/angel4.dtb.o
LD arch/arc/boot/dts/built-in.o
rm arch/arc/boot/dts/angel4.dtb.S <-- forces rebuild next iter
CHK kernel/config_data.h
--------------->8-----------------
This is because *.dts.S is intermediate file in dtb generation and is by
default deleted by make which needs a ".SECONDARY" hint to NOT do so.
This could have ideally been done in scripts/Makefile.lib - for benefit
of all, however .SECONDARY doesn't seem to work with wildcards.
Thanks to Stephen for suggesting .SECONDARY (vs .PRECIOUS) and making
that work using a non wildcard version in arch makefile.
Thanks to James Hogan for pointing out that *.dtb.S now needs to be
added to clean-files
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/boot/dts/Makefile b/arch/arc/boot/dts/Makefile
index 5776835..faf240e 100644
--- a/arch/arc/boot/dts/Makefile
+++ b/arch/arc/boot/dts/Makefile
@@ -8,6 +8,8 @@
obj-y += $(builtindtb-y).dtb.o
targets += $(builtindtb-y).dtb
+.SECONDARY: $(obj)/$(builtindtb-y).dtb.S
+
dtbs: $(addprefix $(obj)/, $(builtindtb-y).dtb)
-clean-files := *.dtb
+clean-files := *.dtb *.dtb.S