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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Sat, 8 Sep 2018 01:47:24 +0900
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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@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Vineet Gupta <vgupta@synopsys.com>,
        Russell King <linux@armlinux.org.uk>,
        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>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        arcml <linux-snps-arc@lists.infradead.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
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        "moderated list:H8/300 ARCHITECTURE" 
        <uclinux-h8-devel@lists.sourceforge.jp>,
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Hi Rob,

2018-09-07 21:17 GMT+09:00 Rob Herring <robh@kernel.org>:
> On Fri, Sep 7, 2018 at 5:33 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>>
>> 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
>
> Any suggestions for how to fix given the problem with depending on
> scripts? I suppose I could make scripts depend on dtc instead, but I'd
> be back to needing to fix cleaning.

How about making 'prepare' depend on 'dtc'?

Then, remove
subdir-$(CONFIG_DTC)         += dtc
from scripts/Makefile

but, add dtc to subdir-


> Or I could just skip removing the
> cross compiler dependency for now.

I want to build scripts/
without target compiler.

modpost is a special host-program
that depends on $(CC).

I will take a look at it
when I find some time.


-- 
Best Regards
Masahiro Yamada