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

From: Lee Jones <lee.jones@linaro.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Chris Brandt <Chris.Brandt@renesas.com>,
	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>
Subject: Re: [PATCH 2/6] ARM: dts: r7s72100: Add SPIBSC clocks
Date: Wed, 4 Dec 2019 08:38:21 +0000	[thread overview]
Message-ID: <20191204083821.GA3468@dell> (raw)
In-Reply-To: <CAMuHMdX_sD+UHnOF+bdbT99zfK1V92+1kVzGnb9JXJyBd-Y5-w@mail.gmail.com>

On Tue, 03 Dec 2019, Geert Uytterhoeven wrote:

> 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?

/**
 * of_clk_detect_critical() - set CLK_IS_CRITICAL flag from Device Tree
 * @np: Device node pointer associated with clock provider
 * @index: clock index
 * @flags: pointer to top-level framework flags
 *
 * Detects if the clock-critical property exists and, if so, sets the
 * corresponding CLK_IS_CRITICAL flag.
 *
 * Do not use this function. It exists only for legacy Device Tree
 * bindings, such as the one-clock-per-node style that are outdated.
 * Those bindings typically put all clock data into .dts and the Linux
 * driver has no clock data, thus making it impossible to set this flag
 * correctly from the driver. Only those drivers may call
 * of_clk_detect_critical from their setup functions.
 *
 * Return: error code or zero on success
 */

If this meets the criteria, the API is pretty simple/self
explanatory.  What are you having trouble with?

> 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
> 

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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