linux-kernel - Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

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Message-ID: <20181003232702.4c18e725@bbrezillon>
Date:   Wed, 3 Oct 2018 23:27:02 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Zhouyang Jia <jiazhouyang09@...il.com>,
        linux-mtd@...ts.infradead.org,
        open list <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

On Wed,  3 Oct 2018 21:38:58 +0200
Ricardo Ribalda Delgado <ricardo.ribalda@...il.com> wrote:

> Add documentation for gpio-addr-flash. This binding allow creating
> flash devices that are paged using GPIOs.
> 
> Cc: devicetree@...r.kernel.org
> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> new file mode 100644
> index 000000000000..5006a26e1753
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> @@ -0,0 +1,54 @@
> +Memory Mapped flash with some address lines addressed using GPIOs
> +
> +Handle the case where a flash device is mostly addressed using physical
> +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> +to a 2MiB memory range and use the GPIOs to select a particular range.
> +
> + - compatible : "cfi-gpio-addr-flash"
> + - reg : Address range of the mtd chip that is memory mapped, this is,
> +   on the previous example 2MiB.
> + - bank-width : Width (in bytes) of the bank.  Equal to the
> +   device width times the number of interleaved chips.
> + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> +   lines. The order goes from LSB to MSB.
> + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".

Looks like other bindings are encoding the probe type in the
compatible [1][2], and we should probably follow what's been done by
others.

> + - #address-cells, #size-cells : Must be present if the device has
> +   sub-nodes representing partitions (see below).  In this case
> +   both #address-cells and #size-cells must be equal to 1.
> +
> +The device tree may optionally contain sub-nodes describing partitions of the
> +address space. Check partition.txt for more details.
> +
> +Example:
> +
> +	flash@...000 {
> +		#address-cells = <1>;
> +		#size-cells = <1>;

You should not have the #address-cells and #size-cells props defined at
this level, it's done in the partitions node already.

> +		compatible = "cfi-gpio-addr-flash";
> +		bank-width = <2>;
> +		reg = < 0x00300000 0x00200000 >;
> +		gpios = <&gpio_0 3 0>, <&gpio_0 4 0>;
> +		partitions {
> +			compatible = "fixed-partitions";
> +			#address-cells = <1>;
> +			#size-cells = <1>;
> +
> +			partition@0 {
> +				reg = < 0x0 0x200000 >;
> +				label = "Golden Bitstream";
> +			};
> +			partition@...000 {
> +				reg = < 0x200000 0x200000 >;
> +				label = "User Bitstream";
> +			};
> +			partition@...000 {
> +				reg = < 0x400000 0x200000 >;
> +				label = "V4L Controls";
> +			};
> +			partition@...000 {
> +				reg = < 0x600000 0x200000 >;
> +				label = "Production Data";
> +			};
> +		}
> +	} ;

[1]https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/mtd/cortina,gemini-flash.txt
[2]https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/mtd/arm-versatile.txt