linux-kernel - Re: [PATCH] mtd: nand: document the NAND controller/NAND chip DT representation

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Date:	Thu, 31 Mar 2016 17:19:42 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Harvey Hunt <harvey.hunt@...tec.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	<linux-mtd@...ts.infradead.org>,
	Richard Weinberger <richard@....at>,
	Mark Rutland <mark.rutland@....com>,
	<devicetree@...r.kernel.org>, Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	<linux-kernel@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
Subject: Re: [PATCH] mtd: nand: document the NAND controller/NAND chip DT
 representation

On Thu, 31 Mar 2016 16:15:26 +0100
Harvey Hunt <harvey.hunt@...tec.com> wrote:

> Hi Boris,
> 
> On 31/03/16 14:57, Boris Brezillon wrote:
> > Standardize the NAND controller/NAND chip DT representation. Now, all new
> > NAND controller drivers should comply with this representation, even if
> > they are only supporting a single NAND chip.
> >
> > Existing drivers can keep support for the old representation (where only
> > the NAND chip was described), but are encouraged to also support the new
> > one.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > ---
> >   Documentation/devicetree/bindings/mtd/nand.txt | 37 +++++++++++++++++++++++++-
> >   1 file changed, 36 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/mtd/nand.txt b/Documentation/devicetree/bindings/mtd/nand.txt
> > index b53f92e..fbf5677 100644
> > --- a/Documentation/devicetree/bindings/mtd/nand.txt
> > +++ b/Documentation/devicetree/bindings/mtd/nand.txt
> > @@ -1,4 +1,23 @@
> > -* MTD generic binding
> > +* NAND chip and NAND controller generic binding
> > +
> > +NAND controller/NAND chip representation:
> > +
> > +The NAND controller should be represented with it's own DT node, and all
> 
> s/it's/its/

Yep, I'll fix that.

> 
> > +NAND chips attached to this controller should be defined as children nodes
> > +of the NAND controller. This representation should be enforced even for
> > +simple controllers supporting only one chip.
> > +
> > +Mandatory NAND controller properties:
> > +- #address-cells: depends on your controller. Should at least be 1 to
> > +		  encode the CS line id.
> > +- #size-cells: depends on your controller. Put zero unless you need a
> > +	       mapping between CS lines and dedicated memory regions
> > +
> > +Optional NAND controller properties
> > +- ranges: only needed if you need to define a mapping between CS lines and
> > +	  memory regions
> > +
> > +Optional NAND chip properties:
> >
> >   - nand-ecc-mode : String, operation mode of the NAND ecc mode.
> >     Supported values are: "none", "soft", "hw", "hw_syndrome", "hw_oob_first",
> > @@ -19,3 +38,19 @@ errors per {size} bytes".
> >   The interpretation of these parameters is implementation-defined, so not all
> >   implementations must support all possible combinations. However, implementations
> >   are encouraged to further specify the value(s) they support.
> > +
> > +Example:
> > +
> > +	nand-controller {
> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +
> > +		/* controller specific properties */
> > +
> > +		nand@0 {
> > +			reg = <0>;
> > +			nand-ecc-mode = "soft_bch";
> > +
> > +			/* controller specific properties */
> 
> Did you mean "chip specific properties"?

No, it's really "controller specific properties". Those are properties
prefixed by the controller vendor name (like 'allwinner,rb' which is
encoding the native ready/busy pin to be attached to this chip).



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com