linux-kernel - Re: [PATCH v3 1/8] rsb: Add generic Reduced Serial Bus (RSB) controller binding documentation

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Date:	Thu, 20 Aug 2015 17:08:45 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Chen-Yu Tsai <wens@...e.org>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-sunxi@...glegroups.com, Hans de Goede <hdegoede@...hat.com>,
	Meng Zhang <kevin@...winnertech.com>, shuge@...winnertech.com,
	kevin.z.m.zh@...il.com
Subject: Re: [PATCH v3 1/8] rsb: Add generic Reduced Serial Bus (RSB)
 controller binding documentation

Hi,

Thanks a lot for working on this.

On Wed, Aug 19, 2015 at 12:20:02PM +0800, Chen-Yu Tsai wrote:
> Reduced Serial Bus is a proprietary 2-line push-pull serial bus
> supporting multiple slave devices.
> 
> It was developed by Allwinner, Inc. and used by Allwinner and X-Powers,
> Inc. for their line of PMICs and other peripheral ICs.
> 
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> ---
>  Documentation/devicetree/bindings/rsb/rsb.txt | 50 +++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/rsb/rsb.txt
> 
> diff --git a/Documentation/devicetree/bindings/rsb/rsb.txt b/Documentation/devicetree/bindings/rsb/rsb.txt
> new file mode 100644
> index 000000000000..0b027948ca9c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rsb/rsb.txt
> @@ -0,0 +1,50 @@
> +Reduced Serial Bus (RSB) Controller
> +
> +This document defines a generic set of bindings for use by RSB controllers.
> +A controller is modelled in device tree as a node with zero or more child
> +nodes, each representing a unique slave device on the bus.
> +
> +Required properties:
> +
> + - #address-cells : must be 2
> + - #size-cells : must be 0
> +
> +Optional properties:
> +
> + - clock-frequency : Desired bus clock frequency in Hz. Maximum is 20 MHz.

What is the default if not set?

> +
> +Child nodes:
> +
> +An RSB controller node can contain zero or more child nodes representing
> +slave devices on the bus.  Child 'reg' properties are specified as a
> +runtime address, hardware address pair. The hardware address is hardwired
> +in the device, which can normally be found in the datasheet. The runtime
> +address is set by software. No 2 devices on the same bus shall have the
> +same runtime address.
> +
> +Valid runtime addresses - There are only 15 valid runtime addresses:
> +
> +    0x17, 0x2d, 0x3a, 0x4e, 0x59, 0x63, 0x74, 0x8b,
> +    0x9c, 0xa6, 0xb1, 0xc5, 0xd2, 0xe8, 0xff
> +
> +It is highly recommended that one choose the same runtime addresses as
> +vendor BSPs use so that a) the addresses remain the same across different
> +software systems, and b) addresses of supported and listed slave devices
> +don't conflict with unsupported or not yet listed devices.

I'd expect to have the hardware address first, but maybe it's just me
:)


> +Example:
> +
> +	rsb@... {
> +		compatible = "...";
> +		reg = <...>;
> +		/* ... */
> +		#address-cells = <2>;
> +		#size-cells = <0>;
> +
> +		pmic@2d {

The unit-address should be 2d,3e3.

> +			compatible = "...";
> +			reg = <0x2d 0x3e3>;
> +
> +			/* ... */
> +		};
> +	};
> -- 
> 2.5.0
> 

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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