linux-kernel - Re: [PATCH 7/7] ARM: dts: sun7i: Enable NAND on Wexler TAB7200

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Message-ID: <20160610085622.GO5242@lukather>
Date:	Fri, 10 Jun 2016 10:56:22 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Aleksei Mamlin <mamlinav@...il.com>
Cc:	Chen-Yu Tsai <wens@...e.org>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Richard Weinberger <richard@....at>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-sunxi@...glegroups.com
Subject: Re: [PATCH 7/7] ARM: dts: sun7i: Enable NAND on Wexler TAB7200

On Thu, Jun 09, 2016 at 11:11:00AM +0300, Aleksei Mamlin wrote:
> On Thu, 9 Jun 2016 00:03:14 +0200
> Maxime Ripard <maxime.ripard@...e-electrons.com> wrote:
> 
> > Hi,
> > 
> > On Mon, Jun 06, 2016 at 01:24:24PM +0300, Aleksei Mamlin wrote:
> > > Enable the NFC and describe the NAND flash connected to this controller.
> > > 
> > > Signed-off-by: Aleksei Mamlin <mamlinav@...il.com>
> > > ---
> > >  arch/arm/boot/dts/sun7i-a20-wexler-tab7200.dts | 41 ++++++++++++++++++++++++++
> > >  1 file changed, 41 insertions(+)
> > > 
> > > diff --git a/arch/arm/boot/dts/sun7i-a20-wexler-tab7200.dts b/arch/arm/boot/dts/sun7i-a20-wexler-tab7200.dts
> > > index 2f6b21a..42aff91 100644
> > > --- a/arch/arm/boot/dts/sun7i-a20-wexler-tab7200.dts
> > > +++ b/arch/arm/boot/dts/sun7i-a20-wexler-tab7200.dts
> > > @@ -159,6 +159,47 @@
> > >  	status = "okay";
> > >  };
> > >  
> > > +&nfc {
> > > +	pinctrl-names = "default";
> > > +	pinctrl-0 = <&nand_pins_a>, <&nand_cs0_pins_a>, <&nand_rb0_pins_a>;
> > > +	status = "okay";
> > > +
> > > +	nand@0 {
> > > +		#address-cells = <2>;
> > > +		#size-cells = <2>;
> > > +		reg = <0>;
> > > +		allwinner,rb = <0>;
> > > +
> > > +		nand-ecc-mode = "hw";
> > > +		nand-on-flash-bbt;
> > > +
> > > +		boot0@0 {
> > > +			label = "boot0";
> > > +			reg = /bits/ 64 <0x0 0x200000>;
> > > +		};
> > > +
> > > +		boot0-rescue@...000 {
> > > +			label = "boot0-rescue";
> > > +			reg = /bits/ 64 <0x200000 0x200000>;
> > > +		};
> > > +
> > > +		uboot@...000 {
> > > +			label = "uboot";
> > > +			reg = /bits/ 64 <0x400000 0x200000>;
> > > +		};
> > > +
> > > +		uboot-rescue@...000 {
> > > +			label = "uboot-rescue";
> > > +			reg = /bits/ 64 <0x600000 0x200000>;
> > > +		};
> > > +
> > > +		main@...000 {
> > > +			label = "main";
> > > +			reg = /bits/ 64 <0x800000 0xff800000>;
> > > +		};
> > > +	};
> > > +};
> > 
> > This feels a bit premature. The two boards you're using have an MLC
> > NAND which is not supported yet. Until there's proper MLC support in
> > the kernel, I'm not sure we want to enable that for end-users when we
> > know that things will get wrong.
> > 
> > However, after discussing this with Boris, I appreciate that we don't
> > have any example available because of this policy for people that want
> > to opt-in anyway.
> > 
> > What we could do is to still mark the status as disabled in the DTS,
> > with a big fat warning as comment just before, so that it requires
> > user action, and that user will have been warned.
> > 
> > Would that work for you?
> > Maxime
> > 
> 
> Let's drop this two patches with boards dts changes until we get proper MLC
> support in kernel.
> 
> As for examples - I'll update linux-sunxi wiki with how to enable NAND 
> controller and describe NAND chips in DTS. People who want to add NAND support 
> to their boards will be warned that it is risky for now.

That works for me too.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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