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Date:	Wed, 29 Oct 2014 14:17:23 +0100
From:	Heiko Stübner <heiko@...ech.de>
To:	Julien CHAUVEAU <julien.chauveau@...-technologies.fr>,
	Max Schwarz <max.schwarz@...ine.de>,
	Addy Ke <addy.ke@...k-chips.com>, wsa@...-dreams.de
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>,
	Russell King <linux@....linux.org.uk>,
	"moderated list:ARM/Rockchip SoC..." 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"open list:OPEN FIRMWARE AND..." <devicetree@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ARM: dts: rockchip: use internal pull-up resistors on I2C busses

Hi Addy, Max, Wolfram,

after Doug's explanation of disfavour [0] and Julien's subsequent response I'm
not sure which direction to go. So if possible I'd like to collect some more
opinions of people knowing a lot more about i2c internals than myself :-) .


Thanks
Heiko


[0] http://lists.infradead.org/pipermail/linux-rockchip/2014-October/000934.html

Am Dienstag, 28. Oktober 2014, 11:36:36 schrieb Julien CHAUVEAU:
> According to the I2C bus specification, it is required to use pull-up
> resistors on the clock and data lines. Probing the I2C busses with
> i2cdetect results in bad results when no devices are connected and no
> external resistors are used.
> 
> This patch configures the I2C busses to use the internal pull-up resistors
> on the RK3066, RK3188 and RK3288 Rockchip processors. It should also be
> noted that these default pull settings match the original configuration on
> these SoCs.
> 
> Below is the results of using i2cdetect on a I2C bus with no devices
> connected before (1) and after (2) applying this patch.
> 
> (1) root@...alhost:~# i2cdetect -y 3
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:          03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
> 10: 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
> 20: 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
> 30: -- -- -- -- -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x81, state: 2
> -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 2
> -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 2
> -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3
> -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3
> -- rk3x-i2c 2005a000.i2c: timeout, ipd: 0x80, state: 3
> ...
> 
> (2) root@...alhost:~# i2cdetect -y 3
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:          -- -- -- -- -- -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
> 
> Signed-off-by: Julien CHAUVEAU <julien.chauveau@...-technologies.fr>
> ---
> Changes since v1:
> - fix the rk3066a pull settings (only available is pull_none/pull_default)
> - remove the warnings in the results of i2cdetect
> 
>  arch/arm/boot/dts/rk3066a.dtsi | 20 ++++++++++----------
>  arch/arm/boot/dts/rk3188.dtsi  | 20 ++++++++++----------
>  arch/arm/boot/dts/rk3288.dtsi  | 24 ++++++++++++------------
>  3 files changed, 32 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/rk3066a.dtsi b/arch/arm/boot/dts/rk3066a.dtsi
> index ad9c2db..dbc1a0b 100644
> --- a/arch/arm/boot/dts/rk3066a.dtsi
> +++ b/arch/arm/boot/dts/rk3066a.dtsi
> @@ -202,36 +202,36 @@
> 
>  		i2c0 {
>  			i2c0_xfer: i2c0-xfer {
> -				rockchip,pins = <RK_GPIO2 28 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO2 29 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO2 28 RK_FUNC_1 &pcfg_pull_default>,
> +						<RK_GPIO2 29 RK_FUNC_1 &pcfg_pull_default>;
>  			};
>  		};
> 
>  		i2c1 {
>  			i2c1_xfer: i2c1-xfer {
> -				rockchip,pins = <RK_GPIO2 30 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO2 31 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO2 30 RK_FUNC_1 &pcfg_pull_default>,
> +						<RK_GPIO2 31 RK_FUNC_1 &pcfg_pull_default>;
>  			};
>  		};
> 
>  		i2c2 {
>  			i2c2_xfer: i2c2-xfer {
> -				rockchip,pins = <RK_GPIO3 0 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO3 1 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO3 0 RK_FUNC_1 &pcfg_pull_default>,
> +						<RK_GPIO3 1 RK_FUNC_1 &pcfg_pull_default>;
>  			};
>  		};
> 
>  		i2c3 {
>  			i2c3_xfer: i2c3-xfer {
> -				rockchip,pins = <RK_GPIO3 2 RK_FUNC_2 &pcfg_pull_none>,
> -						<RK_GPIO3 3 RK_FUNC_2 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO3 2 RK_FUNC_2 &pcfg_pull_default>,
> +						<RK_GPIO3 3 RK_FUNC_2 &pcfg_pull_default>;
>  			};
>  		};
> 
>  		i2c4 {
>  			i2c4_xfer: i2c4-xfer {
> -				rockchip,pins = <RK_GPIO3 4 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO3 5 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO3 4 RK_FUNC_1 &pcfg_pull_default>,
> +						<RK_GPIO3 5 RK_FUNC_1 &pcfg_pull_default>;
>  			};
>  		};
> 
> diff --git a/arch/arm/boot/dts/rk3188.dtsi b/arch/arm/boot/dts/rk3188.dtsi
> index ddaada7..ee2865f 100644
> --- a/arch/arm/boot/dts/rk3188.dtsi
> +++ b/arch/arm/boot/dts/rk3188.dtsi
> @@ -188,36 +188,36 @@
> 
>  		i2c0 {
>  			i2c0_xfer: i2c0-xfer {
> -				rockchip,pins = <RK_GPIO1 24 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO1 25 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO1 24 RK_FUNC_1 &pcfg_pull_up>,
> +						<RK_GPIO1 25 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c1 {
>  			i2c1_xfer: i2c1-xfer {
> -				rockchip,pins = <RK_GPIO1 26 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO1 27 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO1 26 RK_FUNC_1 &pcfg_pull_up>,
> +						<RK_GPIO1 27 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c2 {
>  			i2c2_xfer: i2c2-xfer {
> -				rockchip,pins = <RK_GPIO1 28 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO1 29 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO1 28 RK_FUNC_1 &pcfg_pull_up>,
> +						<RK_GPIO1 29 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c3 {
>  			i2c3_xfer: i2c3-xfer {
> -				rockchip,pins = <RK_GPIO3 14 RK_FUNC_2 &pcfg_pull_none>,
> -						<RK_GPIO3 15 RK_FUNC_2 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO3 14 RK_FUNC_2 &pcfg_pull_up>,
> +						<RK_GPIO3 15 RK_FUNC_2 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c4 {
>  			i2c4_xfer: i2c4-xfer {
> -				rockchip,pins = <RK_GPIO1 30 RK_FUNC_1 &pcfg_pull_none>,
> -						<RK_GPIO1 31 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <RK_GPIO1 30 RK_FUNC_1 &pcfg_pull_up>,
> +						<RK_GPIO1 31 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
> diff --git a/arch/arm/boot/dts/rk3288.dtsi b/arch/arm/boot/dts/rk3288.dtsi
> index 874e66d..9a4b1f7 100644
> --- a/arch/arm/boot/dts/rk3288.dtsi
> +++ b/arch/arm/boot/dts/rk3288.dtsi
> @@ -636,43 +636,43 @@
> 
>  		i2c0 {
>  			i2c0_xfer: i2c0-xfer {
> -				rockchip,pins = <0 15 RK_FUNC_1 &pcfg_pull_none>,
> -						<0 16 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <0 15 RK_FUNC_1 &pcfg_pull_up>,
> +						<0 16 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c1 {
>  			i2c1_xfer: i2c1-xfer {
> -				rockchip,pins = <8 4 RK_FUNC_1 &pcfg_pull_none>,
> -						<8 5 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <8 4 RK_FUNC_1 &pcfg_pull_up>,
> +						<8 5 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c2 {
>  			i2c2_xfer: i2c2-xfer {
> -				rockchip,pins = <6 9 RK_FUNC_1 &pcfg_pull_none>,
> -						<6 10 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <6 9 RK_FUNC_1 &pcfg_pull_up>,
> +						<6 10 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c3 {
>  			i2c3_xfer: i2c3-xfer {
> -				rockchip,pins = <2 16 RK_FUNC_1 &pcfg_pull_none>,
> -						<2 17 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <2 16 RK_FUNC_1 &pcfg_pull_up>,
> +						<2 17 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c4 {
>  			i2c4_xfer: i2c4-xfer {
> -				rockchip,pins = <7 17 RK_FUNC_1 &pcfg_pull_none>,
> -						<7 18 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <7 17 RK_FUNC_1 &pcfg_pull_up>,
> +						<7 18 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};
> 
>  		i2c5 {
>  			i2c5_xfer: i2c5-xfer {
> -				rockchip,pins = <7 19 RK_FUNC_1 &pcfg_pull_none>,
> -						<7 20 RK_FUNC_1 &pcfg_pull_none>;
> +				rockchip,pins = <7 19 RK_FUNC_1 &pcfg_pull_up>,
> +						<7 20 RK_FUNC_1 &pcfg_pull_up>;
>  			};
>  		};

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