linux-kernel - Re: [PATCH 11/11] dt: Exynos: add Snow SPI NOR node.

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Message-Id: <201506041720.54666.marex@denx.de>
Date:	Thu, 4 Jun 2015 17:20:54 +0200
From:	Marek Vasut <marex@...x.de>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Michal Suchanek <hramrach@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene@...nel.org>,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Han Xu <han.xu@...escale.com>, Mark Brown <broonie@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Rafał Miłecki <zajec5@...il.com>,
	Alison Chaiken <alison_chaiken@...tor.com>,
	Huang Shijie <b32955@...escale.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Knut Wohlrab <knut.wohlrab@...bosch.com>,
	"Bean Huo 霍斌斌 (beanhuo)" 
	<beanhuo@...ron.com>, "grmoore@...era.com" <grmoore@...era.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, dmaengine@...r.kernel.org,
	linux-mtd@...ts.infradead.org, linux-spi@...r.kernel.org,
	pavel@...x.de
Subject: Re: [PATCH 11/11] dt: Exynos: add Snow SPI NOR node.

On Thursday, June 04, 2015 at 04:04:18 AM, Krzysztof Kozlowski wrote:
> On 04.06.2015 06:26, Michal Suchanek wrote:
> > The Snow has onboard SPI NOR flash which contains the bootloader.
> > 
> > Add DT node for this flash chip. The flash is rated 133MHz but the pl330
> > controller can transfer only up to 128 bytes at this speed so use more
> > conservative settings. Even at 40MHz pl330 can transfer at most 64k with
> > the current driver.
> > 
> > Signed-off-by: Michal Suchanek <hramrach@...il.com>
> > ---
> > 
> >  arch/arm/boot/dts/exynos5250-snow.dts | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/arch/arm/boot/dts/exynos5250-snow.dts
> > b/arch/arm/boot/dts/exynos5250-snow.dts index 1fa72cf..38e4cda 100644
> > --- a/arch/arm/boot/dts/exynos5250-snow.dts
> > +++ b/arch/arm/boot/dts/exynos5250-snow.dts
> > @@ -691,6 +691,18 @@
> > 
> >  	num-cs = <1>;
> >  	cs-gpios = <&gpa2 5 0>;
> >  	status = "okay";
> > 
> > +		flash: m25p80@0 {
> 
> The indentation looks odd. This should be at the same level as "status".
> 
> > +			#address-cells = <1>;
> > +			#size-cells = <1>;
> > +			compatible = "jedec,spi-nor";
> > +			reg = <0>;
> > +			spi-max-frequency = <40000000>;
> 
> So actually you wanted 133 MHz but as a workaround for DMA issue you use
> 40 MHz, right? Could you add here a small TODO note in comment about it?

I disagree. There is a problem, the problem should actually be analyzed and 
fixed, not just postponed with some TODO nonsense.

Best regards,
Marek Vasut
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