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

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Message-ID: <56FD4099.5040804@imgtec.com>
Date:	Thu, 31 Mar 2016 16:22:01 +0100
From:	Harvey Hunt <harvey.hunt@...tec.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.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

Hi,

On 31/03/16 16:19, Boris Brezillon wrote:
> 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).
>

Okay, I see - I was somewhat confused by it being in the nand chip node, 
but I understand what you mean now.

Thanks,

Harvey