linux/Documentation/devicetree/bindings/i2c/i2c-ocores.txt

Device tree configuration for i2c-ocores

Required properties:
- compatible      : "opencores,i2c-ocores" or "aeroflexgaisler,i2cmst"
- reg             : bus address start and address range size of device
- interrupts      : interrupt number
- opencores,ip-clock-frequency: frequency of the controller clock in Hz;
                    see the note below
- #address-cells  : should be <1>
- #size-cells     : should be <0>

Optional properties:
- clock-frequency : frequency of bus clock in Hz; see the note below.
                    Defaults to 100 KHz when the property is not specified
- reg-shift       : device register offsets are shifted by this value
- reg-io-width    : io register width in bytes (1, 2 or 4)
- regstep         : deprecated, use reg-shift above

Note
clock-frequency property is meant to control the bus frequency for i2c bus
drivers, but it was incorrectly used to specify i2c controller input clock
frequency. So the following rules are set to fix this situation:
- if clock-frequency is present and opencores,ip-clock-frequency is not,
  then clock-frequency specifies i2c controller clock frequency. This is
  to keep backwards compatibility with setups using old DTB. i2c bus
  frequency is fixed at 100 KHz.
- if opencores,ip-clock-frequency is present it specifies i2c controller
  clock frequency. clock-frequency property specifies i2c bus frequency.

Example:

	i2c0: ocores@a0000000 {
		#address-cells = <1>;
		#size-cells = <0>;
		compatible = "opencores,i2c-ocores";
		reg = <0xa0000000 0x8>;
		interrupts = <10>;
		opencores,ip-clock-frequency = <20000000>;

		reg-shift = <0>;	/* 8 bit registers */
		reg-io-width = <1>;	/* 8 bit read/write */

		dummy@60 {
			compatible = "dummy";
			reg = <0x60>;
		};
	};