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Date: Wed, 13 Feb 2013 14:04:18 -0700
From: Stephen Warren <swarren@wwwdotorg.org>
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To: Doug Anderson <dianders@chromium.org>
CC: Wolfram Sang <w.sang@pengutronix.de>, Simon Glass <sjg@chromium.org>,
        Naveen Krishna Chatradhi <ch.naveen@samsung.com>,
        Grant Likely <grant.likely@secretlab.ca>,
        Yuvaraj Kumar <yuvaraj.cd@gmail.com>,
        Ben Dooks <ben.dooks@codethink.co.uk>, u.kleine-koenig@pengutronix.de,
        Mark Brown <broonie@opensource.wolfsonmicro.com>,
        Girish Shivananjappa <girish.shivananjappa@linaro.org>,
        bhushan.r@samsung.com, sreekumar.c@samsung.com,
        Prashanth G <prashanth.g@samsung.com>, Olof Johansson <olof@lixom.net>,
        Daniel Kurtz <djkurtz@chromium.org>,
        Grant Grundler <grundler@chromium.org>,
        Russell King <linux@arm.linux.org.uk>,
        Kukjin Kim <kgene.kim@samsung.com>,
        Rahul Sharma <rahul.sharma@samsung.com>,
        Thomas Abraham <thomas.abraham@linaro.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/4] ARM: dts: Add i2c-arbitrator bus for exynos5250-snow
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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@12CA0000 {
> -		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.