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

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Message-id: <310301ce35da$724dff60$56e9fe20$%kim@samsung.com>
Date:	Wed, 10 Apr 2013 19:59:17 +0900
From:	Kukjin Kim <kgene.kim@...sung.com>
To:	'Doug Anderson' <dianders@...omium.org>,
	'Wolfram Sang' <wsa@...-dreams.de>
Cc:	'Simon Glass' <sjg@...omium.org>,
	'Naveen Krishna Chatradhi' <ch.naveen@...sung.com>,
	grant.likely@...retlab.ca, yuvaraj.cd@...il.com,
	ben.dooks@...ethink.co.uk, u.kleine-koenig@...gutronix.de,
	broonie@...nsource.wolfsonmicro.com,
	girish.shivananjappa@...aro.org, bhushan.r@...sung.com,
	sreekumar.c@...sung.com, prashanth.g@...sung.com, olof@...om.net,
	djkurtz@...omium.org, swarren@...dotorg.org, linux@...ck-us.net,
	'Russell King' <linux@....linux.org.uk>,
	'Thomas Abraham' <thomas.abraham@...aro.org>,
	'Rahul Sharma' <rahul.sharma@...sung.com>,
	'Jingoo Han' <jg1.han@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: RE: [PATCH v5 2/3] ARM: dts: Add i2c-arbitrator bus for exynos5250-snow

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@...omium.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@...A0000 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@...A0000 {
> -		status = "disabled";
> +		samsung,i2c-sda-delay = <100>;
> +		samsung,i2c-max-bus-freq = <66000>;
>  	};
> 
>  	i2c@...B0000 {
> 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@...00000 {
>  		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@...A0000}>;
> +
> +		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

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