linux-kernel - Re: [PATCH v2 2/6] mtd: rawnand: tegra: add devicetree binding

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Date:   Mon, 28 May 2018 00:23:54 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     boris.brezillon@...tlin.com, dwmw2@...radead.org,
        computersforpeace@...il.com, marek.vasut@...il.com,
        robh+dt@...nel.org, mark.rutland@....com, thierry.reding@...il.com,
        mturquette@...libre.com, sboyd@...nel.org, dev@...xeye.de,
        richard@....at, marcel@...wiler.com, krzk@...nel.org,
        digetx@...il.com, benjamin.lindqvist@...ian.se,
        jonathanh@...dia.com, pdeschrijver@...dia.com, pgaikwad@...dia.com,
        mirza.krak@...il.com, linux-mtd@...ts.infradead.org,
        linux-tegra@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 2/6] mtd: rawnand: tegra: add devicetree binding

Hi Stefan,

On Sun, 27 May 2018 23:54:38 +0200, Stefan Agner <stefan@...er.ch>
wrote:

> From: Lucas Stach <dev@...xeye.de>
> 
> This adds the devicetree binding for the Tegra 2 NAND flash
> controller.
> 
> Signed-off-by: Lucas Stach <dev@...xeye.de>
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> ---
>  .../bindings/mtd/nvidia,tegra20-nand.txt      | 62 +++++++++++++++++++
>  1 file changed, 62 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/nvidia,tegra20-nand.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/nvidia,tegra20-nand.txt b/Documentation/devicetree/bindings/mtd/nvidia,tegra20-nand.txt
> new file mode 100644
> index 000000000000..49e472af1b39
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/nvidia,tegra20-nand.txt
> @@ -0,0 +1,62 @@
> +NVIDIA Tegra NAND Flash controller
> +
> +Required properties:
> +- compatible: Must be one of:

Nitpick: just put the compatible here as there is only one?

> +  - "nvidia,tegra20-nand"
> +- reg: MMIO address range
> +- interrupts: interrupt output of the NFC controller
> +- clocks: Must contain an entry for each entry in clock-names.
> +  See ../clocks/clock-bindings.txt for details.
> +- clock-names: Must include the following entries:
> +  - nand
> +- resets: Must contain an entry for each entry in reset-names.
> +  See ../reset/reset.txt for details.
> +- reset-names: Must include the following entries:
> +  - nand
> +
> +Optional children nodes:
> +Individual NAND chips are children of the NAND controller node. Currently
> +only one NAND chip supported.
> +
> +Required children node properties:
> +- reg: An integer ranging from 1 to 6 representing the CS line to use.

>From 1? It usually starts at 0.

> +
> +Optional children node properties:
> +- nand-ecc-mode: String, operation mode of the NAND ecc mode. "hw" by default
> +- nand-ecc-algo: string, algorithm of NAND ECC.
> +		 Supported values are: "rs", "bch".
> +- nand-bus-width : 8 or 16 bus width if not present 8
> +- nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
> +- nand-ecc-strength: integer representing the number of bits to correct
> +		     per ECC step. Supported strength using HW ECC modes are:
> +		     - RS: 4, 6, 8
> +		     - BCH: 4, 8, 14, 16
> +- nand-ecc-step-size: integer representing the number of data bytes
> +		      that are covered by a single ECC step. Must be 512.

Please don't re-explain nand generic DT properties, point to nand.txt
instead.

> +- wp-gpios: GPIO specifier for the write protect pin.
> +
> +Optional child node of NAND chip nodes:
> +Partitions: see partition.txt
> +
> +  Example:
> +	nand@...08000 {
> +		compatible = "nvidia,tegra20-nand";
> +		reg = <0x70008000 0x100>;
> +		interrupts = <GIC_SPI 24 IRQ_TYPE_LEVEL_HIGH>;
> +		clocks = <&tegra_car TEGRA20_CLK_NDFLASH>;
> +		clock-names = "nand";
> +		resets = <&tegra_car 13>;
> +		reset-names = "nand";
> +
> +		nand-chip@0 {
> +			reg = <0>;
> +			#address-cells = <1>;
> +			#size-cells = <1>;
> +			nand-bus-width = <8>;
> +			nand-on-flash-bbt;
> +			nand-ecc-algo = "bch";
> +			nand-ecc-step-size = <512>;

In the driver you only refer to step sizes of 512 B, you can remove the
property from the bindings.

> +			nand-ecc-strength = <8>;
> +			wp-gpios = <&gpio TEGRA_GPIO(S, 0) GPIO_ACTIVE_LOW>;
> +		};
> +	};



-- 
Miquel Raynal, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com