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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Wed, 17 Oct 2018 10:52:14 +0200
Message-ID: <CAMuHMdXNGHZqmMfH=NDVoiX3t3t_TsDHpBr2C4oCELAX=eRrAQ@mail.gmail.com>
Subject: Re: [PATCH] arm64: dts: renesas: r8a779{7|8}0: add MSIOF support
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To: Simon Horman <horms@verge.net.au>
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>, Rob Herring <robh+dt@kernel.org>, Linux-Renesas <linux-renesas-soc@vger.kernel.org>, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@vger.kernel.org>, Magnus Damm <magnus.damm@gmail.com>, Mark Rutland <mark.rutland@arm.com>
List-ID: <devicetree@vger.kernel.org>

Hi Simon,

On Wed, Oct 17, 2018 at 10:13 AM Simon Horman <horms@verge.net.au> wrote:
> On Tue, Oct 16, 2018 at 10:36:33PM +0300, Sergei Shtylyov wrote:
> > Describe MSIOF in the R8A779{7|8}0 device trees.
> >
> > The DMA props are deliberately omitted as the MSIOF DMA doesn't work on
> > R8A77970 (due to IPMMU issue) and the RT-DMAC isn't supported on R8A77980.
>
> For the record: In the short term I'm fine with not enabling DMA if there
> are known problems. But in the long term we should describe DMA in DT as
> the purpose of DT is to describe hardware rather than software.
>
> So please, as follow-up work, lets work towards a solution that allows us
> to describe the hardware in DT.
>
> > Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
> >
> > ---
> > This patch is against the 'renesas-devel-20181015-v4.19-rc8' branch of
> > Simon Horman's 'renesas.git' repo.
> >
> > The MSIOF bindings patch has just been posted...
> >
> >  arch/arm64/boot/dts/renesas/r8a77970.dtsi |   56 ++++++++++++++++++++++++++++++
> >  arch/arm64/boot/dts/renesas/r8a77980.dtsi |   56 ++++++++++++++++++++++++++++++
> >  2 files changed, 112 insertions(+)
> >
> > Index: renesas/arch/arm64/boot/dts/renesas/r8a77970.dtsi
> > ===================================================================
> > --- renesas.orig/arch/arm64/boot/dts/renesas/r8a77970.dtsi
> > +++ renesas/arch/arm64/boot/dts/renesas/r8a77970.dtsi
> > @@ -22,6 +22,10 @@
> >               i2c2 = &i2c2;
> >               i2c3 = &i2c3;
> >               i2c4 = &i2c4;
> > +             spi1 = &msiof0;
> > +             spi2 = &msiof1;
> > +             spi3 = &msiof2;
> > +             spi4 = &msiof3;
>
> Geert, could you comment on these aliases and the similar ones below?
> I'm not seeing them for any other ARM64-based Renesas SoCs.

I2c and spi aliases are "used, but not recommended", cfr.
https://lore.kernel.org/lkml/20181015180046.GA18294@bogus/

Personally (but I'm biased, referring to an email thread I participated in ;-),
I'd only leave serial0 (+ perhaps a 2nd/3th serial port) and ethernet0.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds