RE: [PATCH 2/3] ARM: dts: r8a7743: Add CMT SoC specific support

From: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Simon Horman <horms@verge.net.au>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	Magnus Damm <magnus.damm@gmail.com>,
	Chris Paterson <Chris.Paterson2@renesas.com>,
	Biju Das <biju.das@bp.renesas.com>,
	"linux-renesas-soc@vger.kernel.org"
	<linux-renesas-soc@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: RE: [PATCH 2/3] ARM: dts: r8a7743: Add CMT SoC specific support
Date: Wed, 13 Dec 2017 10:15:39 +0000	[thread overview]
Message-ID: <TY1PR06MB08954C04D41BDA8EFA04E1DFC0350@TY1PR06MB0895.apcprd06.prod.outlook.com> (raw)
In-Reply-To: <CAMuHMdWEFttz_Shve+D1Ku2NoUYX-AomzXY9JFGRjzzM=hOc_A@mail.gmail.com>

Hello Geert,

thank you for your feedback.

> Hi Fabrizio,
>
> On Wed, Dec 13, 2017 at 10:42 AM, Fabrizio Castro
> <fabrizio.castro@bp.renesas.com> wrote:
> >> On Tue, Dec 12, 2017 at 06:49:38PM +0000, Fabrizio Castro wrote:
> >> > Add CMT[01] support to SoC DT.
> >> > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> >> > Reviewed-by: Biju Das <biju.das@bp.renesas.com>
> >> > ---
> >> >  arch/arm/boot/dts/r8a7743.dtsi | 30 ++++++++++++++++++++++++++++++
> >> >  1 file changed, 30 insertions(+)
> >>
> >> I was expecting the cmt nodes to be "disabled" in the SoC file
> >> and then enabled selectively in board files. Am I missing something?
> >
> > Since this component is just a compare and match timer, I  thought there was no harm in enabling it by default in the SoC specific DT.
> > The system will park it and leave its clock disabled until actually needed for something.
> > The user can still disable it in the board specific DT if he/she doesn't mean to even have the option to use it. Do you prefer I left it
> disabled by default?
>
> It's debatable (thus up to Simon the maintainer ;-).
> For I/O devices, we disable them in the SoC .dtsi file.
> For core infrastructure like interrupt, DMA, and GPIO controllers, we keep
> them enabled.
>
> Timers are core functionality, but who's actually using these timers?

I don't have a use case in mind unfortunately, but it's still core functionality and pretty harmless as far as I can tell. Let's see what Simon thinks about this.

Thanks,
Fab

>
> 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

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