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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Fri, 7 Sep 2018 19:32:06 +0900
Message-ID: <CAK7LNARD+_kV=XtJ66mZBU-CPMQgWF+oQtv4bGKaGGARNwzXiQ@mail.gmail.com>
Subject: Re: [PATCH v2 6/9] kbuild: consolidate Devicetree dtb build rules
To:     Rob Herring <robh@kernel.org>
Cc:     DTML <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
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        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Michal Simek <monstr@monstr.eu>,
        Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        James Hogan <jhogan@kernel.org>,
        Ley Foon Tan <lftan@altera.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
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2018-09-06 8:53 GMT+09:00 Rob Herring <robh@kernel.org>:
> There is nothing arch specific about building dtb files other than their
> location under /arch/*/boot/dts/. Keeping each arch aligned is a pain.
> The dependencies and supported targets are all slightly different.
> Also, a cross-compiler for each arch is needed, but really the host
> compiler preprocessor is perfectly fine for building dtbs. Move the
> build rules to a common location and remove the arch specific ones. This
> is done in a single step to avoid warnings about overriding rules.
>
> The build dependencies had been a mixture of 'scripts' and/or 'prepare'.
> These pull in several dependencies some of which need a target compiler
> (specifically devicetable-offsets.h) and aren't needed to build dtbs.
> All that is really needed is dtc, so adjust the dependencies to only be
> dtc.
>
> This change enables support 'dtbs_install' on some arches which were
> missing the target.
>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Vineet Gupta <vgupta@synopsys.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Michal Simek <monstr@monstr.eu>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Burton <paul.burton@mips.com>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: Ley Foon Tan <lftan@altera.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Chris Zankel <chris@zankel.net>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> Cc: linux-kbuild@vger.kernel.org
> Cc: linux-snps-arc@lists.infradead.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: uclinux-h8-devel@lists.sourceforge.jp
> Cc: linux-mips@linux-mips.org
> Cc: nios2-dev@lists.rocketboards.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-xtensa@linux-xtensa.org
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
> Please ack so I can take the whole series via the DT tree.
>
> v2:
>  - Fix $arch/boot/dts path check for out of tree builds
>  - Fix dtc dependency for building built-in dtbs
>  - Fix microblaze built-in dtb building


This breaks parallel building
because two threads could descend into scripts/dtc
at the same time.

'all' depends on both 'scripts' and 'dtc'.

* 'scripts' target -- descends into scripts/, then scripts/dtc
* 'dtc' target     -- descents into scripts/dtc directly


-- 
Best Regards
Masahiro Yamada