From: Vineet Gupta <vgupta@synopsys.com>
Date: Tue, 16 Apr 2013 03:13:58 +0000 (+0530)
Subject: ARC: [kbuild] Avoid DTB rebuilds if DTS are untouched
X-Git-Tag: v3.10-rc1~16^2~29
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a89516b31c8c0a41b4955fbcee764901232d71b1;p=profile%2Fivi%2Fkernel-x86-ivi.git

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 @@ endif
 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