linux-kernel - Re: [PATCH 5/6] clk: emev2: Add support for emev2 SMU clocks with DT

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Message-ID: <690317658.gaTDz3TliP@avalon>
Date:	Tue, 01 Oct 2013 14:27:51 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	takasi-y@....dti.ne.jp, SH-Linux <linux-sh@...r.kernel.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Shinya Kuribayashi <shinya.kuribayashi.px@...esas.com>,
	devicetree@...r.kernel.org, linux-serial@...r.kernel.org,
	Simon Horman <horms@...ge.net.au>,
	Paul Mundt <lethal@...ux-sh.org>,
	Mike Turquette <mturquette@...aro.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 5/6] clk: emev2: Add support for emev2 SMU clocks with DT

Hi Yoshii-san,

Thank you for the patch.

(CC'ing LAMK as a generic CCF question follows)

On Tuesday 01 October 2013 18:15:26 Magnus Damm wrote:
> On Tue, Sep 24, 2013 at 1:15 PM,  <takasi-y@....dti.ne.jp> wrote:
> > Common clock framework version of emev2 clock support.
> > smu_clkdiv and smu_gclk are handled.
> > So far, reparent is not implemented, and is fixed to index #0.
> > SMU and small numbers of clocks are described in emev2.dtsi.
> > 
> > That function and numbers of clocks are equivalent to current
> > sh-clkfwk version. It is just enough to run kzm9d-reference.
> > 
> > Signed-off-by: Takashi Yoshii <takashi.yoshii.zj@...esas.com>
> > ---
> > 
> >  arch/arm/boot/dts/emev2.dtsi     |  84 +++++++++++++++++++++++++++++++
> >  drivers/clk/Makefile             |   2 +
> >  drivers/clk/shmobile/Makefile    |   5 ++
> >  drivers/clk/shmobile/clk-emev2.c | 104 ++++++++++++++++++++++++++++++++++
> >  4 files changed, 195 insertions(+)
> >  create mode 100644 drivers/clk/shmobile/Makefile
> >  create mode 100644 drivers/clk/shmobile/clk-emev2.c
> 
> Hi Yoshii-san,
> 
> Thanks for your efforts on this. I'm very pleased to see that you describe
> the clock topology using DT.

What is the generally accepted practice when an IP core provides a large 
number of clocks, with either one register or one register bit dedicated to 
each clock ? Should each clock be described as one DT node, or should the IP 
core be described by a single DT node ?

I also see both platforms using CLK_OF_DECLARE and platforms calling a clock 
init function provided by drivers/clk/<platform>.c in the SoC setup code in 
arch/arm/. What is the preferred practice there ?

> In general I think your patch looks fine, but I have some comment related to
> the multiplatform integration, please see below.
> 
> > diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> > index 7b11106..3e64ac4 100644
> > --- a/drivers/clk/Makefile
> > +++ b/drivers/clk/Makefile
> > @@ -32,6 +32,8 @@ obj-$(CONFIG_ARCH_VT8500)     += clk-vt8500.o
> > 
> >  obj-$(CONFIG_ARCH_ZYNQ)                += zynq/
> >  obj-$(CONFIG_ARCH_TEGRA)       += tegra/
> >  obj-$(CONFIG_PLAT_SAMSUNG)     += samsung/
> > 
> > +obj-$(CONFIG_ARCH_SHMOBILE)    += shmobile/
> > +obj-$(CONFIG_ARCH_SHMOBILE_MULTI)      += shmobile/
> 
> Here I believe it is enough that you only use
> CONFIG_ARCH_SHMOBILE_MULTI. Building common clocks to coexist with the
> old legacy board code does not make any sense IMO. If you think it
> makes sense for some reason, please explain why. =)
> 
> > diff --git a/drivers/clk/shmobile/Makefile b/drivers/clk/shmobile/Makefile
> > new file mode 100644
> > index 0000000..6a26eb6
> > --- /dev/null
> > +++ b/drivers/clk/shmobile/Makefile
> > @@ -0,0 +1,5 @@
> > +ifeq ($(CONFIG_COMMON_CLK), y)
> > +obj-$(CONFIG_ARCH_EMEV2)       += clk-emev2.o
> > +endif
> 
> I don't think you would need the above ifeq/endif wrapper if you only
> used CONFIG_ARCH_SHMOBILE_MULTI above.
> 
> Apart from that it looks good to me. And, yes, I have tested this on
> my KZM9D board together with multiplatform and it works very well!

-- 
Regards,

Laurent Pinchart

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