linux-arkmicro/u-boot/doc/device-tree-bindings/i2c/i2c.txt

U-Boot I2C
----------

U-Boot's I2C model has the concept of an offset within a chip (I2C target
device). The offset can be up to 4 bytes long, but is normally 1 byte,
meaning that offsets from 0 to 255 are supported by the chip. This often
corresponds to register numbers.

Apart from the controller-specific I2C bindings, U-Boot supports a special
property which allows the chip offset length to be selected.

Optional properties:
- u-boot,i2c-offset-len - length of chip offset in bytes. If omitted the
    default value of 1 is used.
- gpios = <sda ...>, <scl ...>;
  pinctrl-names = "default", "gpio";
  pinctrl-0 = <&i2c_xfer>;
  pinctrl-1 = <&i2c_gpio>;
    Pin description for I2C bus software deblocking.


Example
-------

i2c4: i2c@12ca0000 {
	cros-ec@1e {
		reg = <0x1e>;
		compatible = "google,cros-ec";
		i2c-max-frequency = <100000>;
		u-boot,i2c-offset-len = <0>;
		ec-interrupt = <&gpx1 6 GPIO_ACTIVE_LOW>;
	};
};

&i2c1 {
	pinctrl-names = "default", "gpio";
	pinctrl-0 = <&i2c1_xfer>;
	pinctrl-1 = <&i2c1_gpio>;
	gpios = <&gpio1 26 GPIO_ACTIVE_LOW>, /* SDA */
		<&gpio1 27 GPIO_ACTIVE_LOW>; /* SCL */
};