linux-kernel - Re: [PATCH v1 2/4] ARM: dts: Add i2c-arbitrator bus for exynos5250-snow

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Message-ID: <511BFFD2.8090102@wwwdotorg.org>
Date:	Wed, 13 Feb 2013 14:04:18 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Doug Anderson <dianders@...omium.org>
CC:	Wolfram Sang <w.sang@...gutronix.de>,
	Simon Glass <sjg@...omium.org>,
	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Yuvaraj Kumar <yuvaraj.cd@...il.com>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	u.kleine-koenig@...gutronix.de,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Girish Shivananjappa <girish.shivananjappa@...aro.org>,
	bhushan.r@...sung.com, sreekumar.c@...sung.com,
	Prashanth G <prashanth.g@...sung.com>,
	Olof Johansson <olof@...om.net>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Grant Grundler <grundler@...omium.org>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Thomas Abraham <thomas.abraham@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/4] ARM: dts: Add i2c-arbitrator bus for exynos5250-snow

On 02/13/2013 11:02 AM, Doug Anderson wrote:
> We need to use the i2c-arbitrator to talk to any of the devices on i2c
> bus 4 on exynos5250-snow so that we don't confuse the embedded
> controller (EC).  Add the i2c-arbitrator to the device tree.  As we
> add future devices (keyboard, sbs, tps65090) we'll add them on top of
> this.
> 
> The arbitrated bus is numbered 104 simply as a convenience to make it
> easier for people poking around to guess that it might have something
> to do with the physical bus 4.
> 
> The addition is split between the cros5250-common and the snow device
> tree file since not all cros5250-class devices use arbitration.

> diff --git a/arch/arm/boot/dts/cros5250-common.dtsi b/arch/arm/boot/dts/cros5250-common.dtsi

>  	i2c@...A0000 {
> -		status = "disabled";
> +		samsung,i2c-sda-delay = <100>;
> +		samsung,i2c-max-bus-freq = <66000>;

Shouldn't that use the standard clock-frequency property?

> diff --git a/arch/arm/boot/dts/exynos5250-snow.dts b/arch/arm/boot/dts/exynos5250-snow.dts

> +	i2c-arbitrator {
> +		compatible = "i2c-arbitrator";
> +		#address-cells = <1>;
> +		#size-cells = <0>;

> +		/* Use ID 104 as a hint that we're on physical bus 4 */
> +		i2c_104: i2c@0 {

Does something use that hint? It sounds a little odd.
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