RE: [PATCH v5 2/3] ARM: dts: Add i2c-arbitrator bus for exynos5250-snow

From: Kukjin Kim <kgene.kim@samsung.com>
To: "'Doug Anderson'" <dianders@chromium.org>,
	"'Wolfram Sang'" <wsa@the-dreams.de>
Cc: "'Simon Glass'" <sjg@chromium.org>,
	"'Naveen Krishna Chatradhi'" <ch.naveen@samsung.com>,
	grant.likely@secretlab.ca, yuvaraj.cd@gmail.com,
	ben.dooks@codethink.co.uk, u.kleine-koenig@pengutronix.de,
	broonie@opensource.wolfsonmicro.com,
	girish.shivananjappa@linaro.org, bhushan.r@samsung.com,
	sreekumar.c@samsung.com, prashanth.g@samsung.com, olof@lixom.net,
	djkurtz@chromium.org, swarren@wwwdotorg.org, linux@roeck-us.net,
	"'Russell King'" <linux@arm.linux.org.uk>,
	"'Thomas Abraham'" <thomas.abraham@linaro.org>,
	"'Rahul Sharma'" <rahul.sharma@samsung.com>,
	"'Jingoo Han'" <jg1.han@samsung.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: RE: [PATCH v5 2/3] ARM: dts: Add i2c-arbitrator bus for exynos5250-snow
Date: Wed, 10 Apr 2013 19:59:17 +0900	[thread overview]
Message-ID: <310301ce35da$724dff60$56e9fe20$%kim@samsung.com> (raw)
In-Reply-To: <1365543270-10736-2-git-send-email-dianders@chromium.org>

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.
> 
> Signed-off-by: Doug Anderson <dianders@chromium.org>

I'm fine on 2nd and 3rd patches. Shall I take only two patches without 1st
one in samsung tree?

- Kukjin

> ---
> Changes in v5:
> - Adjust bindings as per Wolfram Sang.
> 
> Changes in v4:
> - Changed mux gpio syntax to work atop Thomas's "ARM: dts: add pin
>   state information in client nodes for Exynos5 platforms"; avoid
>   adding gpios property to i2c@12CA0000 for the same reason.
> 
> Changes in v3: None
> Changes in v2:
> - Use new device tree property names / compatible string.
> - Include that the GPIOs for arbitration are active low.
> 
>  arch/arm/boot/dts/cros5250-common.dtsi |  3 ++-
>  arch/arm/boot/dts/exynos5250-snow.dts  | 25 +++++++++++++++++++++++++
>  2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/boot/dts/cros5250-common.dtsi
> b/arch/arm/boot/dts/cros5250-common.dtsi
> index 8a5b3a6..0a61bbb 100644
> --- a/arch/arm/boot/dts/cros5250-common.dtsi
> +++ b/arch/arm/boot/dts/cros5250-common.dtsi
> @@ -193,7 +193,8 @@
>  	};
> 
>  	i2c@12CA0000 {
> -		status = "disabled";
> +		samsung,i2c-sda-delay = <100>;
> +		samsung,i2c-max-bus-freq = <66000>;
>  	};
> 
>  	i2c@12CB0000 {
> diff --git a/arch/arm/boot/dts/exynos5250-snow.dts
> b/arch/arm/boot/dts/exynos5250-snow.dts
> index 581ffae..fa85f58 100644
> --- a/arch/arm/boot/dts/exynos5250-snow.dts
> +++ b/arch/arm/boot/dts/exynos5250-snow.dts
> @@ -16,6 +16,10 @@
>  	model = "Google Snow";
>  	compatible = "google,snow", "samsung,exynos5250";
> 
> +	aliases {
> +		i2c104 = &i2c_104;
> +	};
> +
>  	pinctrl@11400000 {
>  		sd3_clk: sd3-clk {
>  			samsung,pin-drv = <0>;
> @@ -44,6 +48,27 @@
>  		};
>  	};
> 
> +	i2c-arbitrator {
> +		compatible = "i2c-arb-gpio-challenge";
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		i2c-parent = <&{/i2c@12CA0000}>;
> +
> +		our-claim-gpio = <&gpf0 3 1>;
> +		their-claim-gpios = <&gpe0 4 1>;
> +		slew-delay-us = <10>;
> +		wait-retry-us = <3000>;
> +		wait-free-us = <50000>;
> +
> +		/* Use ID 104 as a hint that we're on physical bus 4 */
> +		i2c_104: i2c@0 {
> +			reg = <0>;
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +		};
> +	};
> +
>  	/*
>  	 * On Snow we've got SIP WiFi and so can keep drive strengths low
> to
>  	 * reduce EMI.
> --
> 1.8.1.3