Re: [PATCH 2/6] ARM: dts: r7s72100: Add SPIBSC clocks

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Chris Brandt <Chris.Brandt@renesas.com>
Cc: Mark Brown <broonie@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	linux-spi <linux-spi@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	Mason Yang <masonccyang@mxic.com.tw>,
	Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
	Lee Jones <lee.jones@linaro.org>
Subject: Re: [PATCH 2/6] ARM: dts: r7s72100: Add SPIBSC clocks
Date: Tue, 3 Dec 2019 20:12:52 +0100	[thread overview]
Message-ID: <CAMuHMdX_sD+UHnOF+bdbT99zfK1V92+1kVzGnb9JXJyBd-Y5-w@mail.gmail.com> (raw)
In-Reply-To: <TY1PR01MB1562F44E4FB80788922CE9BE8A420@TY1PR01MB1562.jpnprd01.prod.outlook.com>

Hi Chris,

CC Lee (for clock-critical)

On Tue, Dec 3, 2019 at 7:58 PM Chris Brandt <Chris.Brandt@renesas.com> wrote:
> On Tue, Dec 3, 2019, Geert Uytterhoeven wrote:
> > > +                       reg = <0x3fefa000 0x100>, <0x18000000
> > > + 0x4000000>;
> >
> > The second region conflicts with the XIP flash@18000000 in
> > arch/arm/boot/dts/r7s72100-gr-peach.dts.
> > Yes, I know it is the same device ;-)
>
> Is that just an FYI?? Or do you have some suggestion??

Can the flash subnode be compatible with "mtd-rom", even if the parent node
is kept disabled?

> > > +                       clock-critical = <4>; /* spibsc0 */
> >
> > Iff we go this clock-critical route, I think this should be specified in the
> > board-specific .dts instead of in the SoC-specific .dtsi.
>
> OK, that's fine. It makes more sense to be in the .dts because it's a board
> design decision. I will remove it from the patch.
>
> The one 'tricky' thing is that the <4> is the index into the number of clocks.
>
> So in the Renesas BSP where it includes the VDC5 LCD controllers,
>
> clock-output-names = "i2c0", "i2c1", "i2c2", "i2c3", "vdc50", "vdc51", "spibsc0", "spibsc1";
>
> the <4> needs to become a <6>.

Unless you pass "clkidx" instead of "i" to of_clk_detect_critical() in [1],
and use "clock-critical = <R7S72100_CLK_SPIBSC0>" in DT?

Unfortunately the exact semantics of clock-critical were never documented.
Lee?

Thanks!

[1] "[PATCH 1/6] clk: renesas: mstp: Add critical clock from device
tree support"
    https://lore.kernel.org/linux-renesas-soc/20191203034519.5640-2-chris.brandt@renesas.com/

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