linux-kernel - Re: [PATCH] doc: devicetree: Add bindings documentation for omap-des driver

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Date:	Mon, 11 Nov 2013 11:01:06 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Joel Fernandes <joelf@...com>
Cc:	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"santosh.shilimkar@...com" <santosh.shilimkar@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Pawel Moll <Pawel.Moll@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Landley <rob@...dley.net>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] doc: devicetree: Add bindings documentation for
 omap-des driver

Hi Joel,

I realise I'm a little late in replying to this, but there are a few
things that would be nice to fix up.

On Fri, Nov 08, 2013 at 12:37:09AM +0000, Joel Fernandes wrote:
> Add documentation for the generic OMAP DES crypto module describing the device
> tree bindings.
> 
> Signed-off-by: Joel Fernandes <joelf@...com>
> ---
>  .../devicetree/bindings/crypto/omap-des.txt        | 28 ++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/crypto/omap-des.txt
> 
> diff --git a/Documentation/devicetree/bindings/crypto/omap-des.txt b/Documentation/devicetree/bindings/crypto/omap-des.txt
> new file mode 100644
> index 0000000..0637647
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/crypto/omap-des.txt
> @@ -0,0 +1,28 @@
> +OMAP SoC DES crypto Module
> +
> +Required properties:
> +
> +- compatible : Should be "ti,omap4-des"

Nit: s/Should be/Should contain/

> +- ti,hwmods: Name of the hwmod associated with the DES module
> +- reg : Offset and length of the register set for the module
> +- interrupts : the interrupt-specifier for the DES module

Just to check: there's only one interrupt?

> +- clocks : phandle to the functional clock node of the DES module
> +- clock-names : Name of the functional clock

What name is expected here? The intent of clock-names is to describe
which clock input lines the clocks are wired to, so this should be
well-defined.

>From the looks of the example, the clock input is called "fck". Is that
correct?

When you have clock-names, the nicest thing to do is to define clocks
in terms of clock-names. Something like:

- clocks: A phandle + clock-specifier pair for each entry in
  clock-names.

- clock-names: Should contain:
  * "fck" for the functional clock

Which implies that the correct way to find clocks is to look in
clock-names first to find the clock's index, rather than grabbing the
clock by index. This makes it far easier to add/remove/change clocks in
future.

> +
> +Optional properties:
> +- dmas: DMA specifiers for tx and rx dma. See the DMA client binding,
> +	Documentation/devicetree/bindings/dma/dma.txt

Similarly here it would be nice to have dmas refer to dma-names for
the description of which dmas exist.

> +- dma-names: DMA request names should include "tx" and "rx" if present
> +
> +Example:
> +	/* DRA7xx SoC */
> +	des: des@...a5000 {
> +		compatible = "ti,omap4-des";
> +		ti,hwmods = "des";
> +		reg = <0x480a5000 0xa0>;
> +		interrupts = <GIC_SPI 82 IRQ_TYPE_LEVEL_HIGH>;
> +		dmas = <&sdma 117>, <&sdma 116>;
> +		dma-names = "tx", "rx";
> +		clocks = <&l3_iclk_div>;
> +		clock-names = "fck";
> +	};

Cheers,
Mark.
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