Re: [PATCH v2] ARM: dts: rockchip: use internal pull-up resistors on I2C busses
From: Heiko Stübner
Date: Wed Oct 29 2014 - 09:14:32 EST
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@localhost:~# 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@localhost:~# 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@xxxxxxxxxxxxxxxxxxx>
> ---
> 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>;
> };
> };
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/