Re: [PATCH] arm64: dts: imx8mq-zii-ultra: Operate I2C at 100kHz

[Lucas Stach <l.stach@pengutronix.de>]

Hi Fabio,

Am Montag, den 13.05.2019, 11:02 -0300 schrieb Fabio Estevam:
> According to the i.MX8M errata document [1], there is an I2C spec
> violation when the I2C clock frequency is 400 kHz:
> 
> "e7805: I2C: When the I2C clock speed is configured for 400 kHz, the
> SCL low period violates the I2C spec of 1.3 uS min"

> Avoid this problem by running I2C at 100 kHz instead.

Does this fix a real bug? The same issue is present with the i.MX6 I2C
controllers, but we are still running a lot of i2c busses on i.MX6
based boards at 400kHz, with no issues whatsoever.

Regards,
Lucas

> [1] https://www.nxp.com/docs/en/errata/IMX8MDQLQ_1N14W.pdf
> 
> Signed-off-by: Fabio Estevam <festevam@gmail.com>
> ---
>  arch/arm64/boot/dts/freescale/imx8mq-zii-ultra.dtsi | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8mq-zii-ultra.dtsi
> b/arch/arm64/boot/dts/freescale/imx8mq-zii-ultra.dtsi
> index 7a1706f969f0..8603fb1a78d0 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mq-zii-ultra.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mq-zii-ultra.dtsi
> @@ -253,14 +253,14 @@
>  };
>  
>  &i2c1 {
> -	clock-frequency = <400000>;
> +	clock-frequency = <100000>;
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_i2c1>;
>  	status = "okay";
>  };
>  
>  &i2c2 {
> -	clock-frequency = <400000>;
> +	clock-frequency = <100000>;
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_i2c2>;
>  	status = "okay";
> @@ -376,7 +376,7 @@
>  };
>  
>  &i2c4 {
> -	clock-frequency = <400000>;
> +	clock-frequency = <100000>;
>  	pinctrl-names = "default";
>  	pinctrl-0 = <&pinctrl_i2c4>;
>  	status = "okay";

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