Re: [RFC PATCH 1/2] dt-bindings: mtd: Add Cavium SOCs NAND bindings

[Boris Brezillon <boris.brezillon@free-electrons.com>]

Hi Jan,

On Mon, 27 Mar 2017 18:05:23 +0200
Jan Glauber <jglauber@cavium.com> wrote:

> Add device tree binding description for Cavium SOC nand flash controller.
> 
> CC: Rob Herring <robh+dt@kernel.org>
> CC: Mark Rutland <mark.rutland@arm.com>
> CC: devicetree@vger.kernel.org
> 
> Signed-off-by: Jan Glauber <jglauber@cavium.com>
> ---
>  .../devicetree/bindings/mtd/cavium_nand.txt        | 32 ++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/cavium_nand.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/cavium_nand.txt b/Documentation/devicetree/bindings/mtd/cavium_nand.txt
> new file mode 100644
> index 0000000..4698d1f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/cavium_nand.txt
> @@ -0,0 +1,32 @@
> +* Cavium NAND controller
> +
> +Required properties:
> +
> +- compatible:		should be "cavium,cn8xxx-nand"
> +- reg:			PCI devfn
> +- clocks:		must contain system clock
> +- #address-cells:	<1>
> +- #size-cells:		<0>
> +
> +The nand flash controller may contain up to 8 subnodes representing
> +NAND flash chips. Their properties are as follows.
> +
> +Required properties:
> +- compatible:		should be "cavium,nandcs"

Why do you need a compatible here? All sub-nodes should be representing
NAND devices connected to the NAND controller. If you need an extra
subnode to represent something that is not a NAND device, then it should
not have a reg property, so testing if reg is present to detect if the
subnode is reprensenting a NAND device should be enough.

Am I missing something?

> +- reg:			a single integer representing the chip-select number
> +- nand-ecc-mode:	see nand.txt
> +
> +Example:
> +
> +nfc: nand@b,0 {

        ^ nand-controller@xxx

> +	compatible = "cavium,cn8xxx-nand";
> +	reg = <0x5800 0 0 0 0>;
> +	clocks = <&sclk>;
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +
> +	nand@1 {
> +		compatible = "cavium,nandcs";
> +		reg = <1>;
> +		nand-ecc-mode = "on-die";
> +};