linux-kernel - Re: [PATCH 2/5] arm64, thunder: Add initial dts for Cavium Thunder SoC

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Message-ID: <CAOesGMh3TEKZkyPjopfSm07C2ydw5=2VrzY0xQ=9jkhoA-Z_kQ@mail.gmail.com>
Date:	Thu, 28 Aug 2014 16:01:08 -0700
From:	Olof Johansson <olof@...om.net>
To:	Robert Richter <rric@...nel.org>
Cc:	Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Arnd Bergmann <arnd@...db.de>, Pawel Moll <Pawel.Moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Radha Mohan Chintakuntla <rchintakuntla@...ium.com>,
	Robert Richter <rrichter@...ium.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/5] arm64, thunder: Add initial dts for Cavium Thunder SoC

On Thu, Aug 28, 2014 at 11:14 AM, Robert Richter <rric@...nel.org> wrote:
> On 28.08.14 09:31:43, Olof Johansson wrote:
>> On Thu, Aug 28, 2014 at 9:25 AM, Mark Rutland <mark.rutland@....com> wrote:
>> > On Thu, Aug 28, 2014 at 05:15:56PM +0100, Robert Richter wrote:
>> >> Olof,
>> >>
>> >> On 30.07.14 11:14:23, Olof Johansson wrote:
>> >> > On Wed, Jul 30, 2014 at 8:06 AM, Robert Richter <rric@...nel.org> wrote:
>> >> > > From: Radha Mohan Chintakuntla <rchintakuntla@...ium.com>
>> >> > >
>> >> > > Add initial device tree nodes for Cavium Thunder SoCs with support of
>> >> > > 48 cores and gicv3. The dts file requires further changes, esp. for
>> >> > > pci, gicv3-its and smmu. This changes will be added later together
>> >> > > with the device drivers.
>> >> > >
>> >> > > Signed-off-by: Radha Mohan Chintakuntla <rchintakuntla@...ium.com>
>> >> > > Signed-off-by: Robert Richter <rrichter@...ium.com>
>> >> > > ---
>> >> > >  arch/arm64/boot/dts/Makefile         |   1 +
>> >> > >  arch/arm64/boot/dts/thunder-88xx.dts | 387 +++++++++++++++++++++++++++++++++++
>> >> > >  2 files changed, 388 insertions(+)
>> >> > >  create mode 100644 arch/arm64/boot/dts/thunder-88xx.dts
>> >> > >
>> >> > > diff --git a/arch/arm64/boot/dts/Makefile b/arch/arm64/boot/dts/Makefile
>> >> > > index c52bdb051f66..f8001a62029c 100644
>> >> > > --- a/arch/arm64/boot/dts/Makefile
>> >> > > +++ b/arch/arm64/boot/dts/Makefile
>> >> > > @@ -1,3 +1,4 @@
>> >> > > +dtb-$(CONFIG_ARCH_THUNDER) += thunder-88xx.dtb
>> >> > >  dtb-$(CONFIG_ARCH_VEXPRESS) += rtsm_ve-aemv8a.dtb foundation-v8.dtb
>> >> > >  dtb-$(CONFIG_ARCH_XGENE) += apm-mustang.dtb
>> >> >
>> >> > Oh, and:
>> >> >
>> >> > Let's fix the mistake we made on 32-bit here (that we can't undo
>> >> > unless we move all dts files now, which is too much churn), and put
>> >> > each SoC vendor in its own subdirectory.
>> >> >
>> >> > So, please add a arch/arm64/boot/dts/cavium/ directory, add a Makefile
>> >> > and the dts there.
>> >> >
>> >> > We should move vexpress under arm/   and xgene under apm/ too.
>> >>
>> >> I was looking into this. It turned out that this would introduce more
>> >> pain than it solves. The problem with introducing vendor subdirs for
>> >> .dts files is that this will require also subdirs for .dtb files to
>> >> avoid name conflicts. This means that dtb files are no longer in a
>> >> single directory. Current build scripts and makefiles rely on this.
>> >> E.g.:
>> >>
>> >>  scripts/Makefile.lib:$(obj)/%.dtb.S: $(obj)/%.dtb
>> >>
>> >> Thus, the introduction of vendor subdirs is not easy to implement and
>> >> may break existing workflows. Also, no other arch has vendor subdirs.
>> >>
>> >> A solution would be to have a naming scheme for dts files which
>> >> requires the vendor in the file name, such as cavium-thunder-88xx.dtb.
>> >> Though, these long names may look a bit ugly.
>> >>
>> >> Hmm... Any thoughts?
>> >
>> > That would make it possible to search, but the number of files in one
>> > place might become somewhat overwelming (which I believe was Olof's
>> > concern).
>> >
>> > Olof, thoughts?
>>
>> Yeah, on 32 bit we've got an ever-growing and very large directory
>> today that is becoming a headache. Carving it up in directories to
>> reduce plain directory size would come a long way.
>>
>> I think we would catch name conflicts quickly with the automatic
>> builders we have today -- and it's likely that the files will have a
>> platform prefix anyway so it shouldn't be a big issue. I think we can
>> live with that.
>
> So you mean, having the source files with subdirectories, but the dtb
> files in a single obj dir?

Thinking about it a bit more, the even more obvious solution that I
for some reason didn't think of at the time, is to have the
dtbs_install target create the appropriate subdirectories on the
install side, so that the structure is preserved.

That comes a bit closer to how modules are handled as well.


-Olof
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