dt-bindings: mfd: Convert ChromeOS EC bindings to json-schema

ChromeOS Embedded Controller

Google's ChromeOS EC is a Cortex-M device which talks to the AP and

implements various function such as keyboard and battery charging.

The EC can be connect through various means (I2C, SPI, LPC, RPMSG) and the

compatible string used depends on the interface. Each connection method has

its own driver which connects to the top level interface-agnostic EC driver.

Other Linux driver (such as cros-ec-keyb for the matrix keyboard) connect to

the top-level driver.

Required properties (I2C):

- compatible: "google,cros-ec-i2c"

- reg: I2C slave address

Required properties (SPI):

- compatible: "google,cros-ec-spi"

- reg: SPI chip select

Required properties (RPMSG):

- compatible: "google,cros-ec-rpmsg"

Optional properties (SPI):

- google,cros-ec-spi-pre-delay: Some implementations of the EC need a little

  time to wake up from sleep before they can receive SPI transfers at a high

  clock rate. This property specifies the delay, in usecs, between the

  assertion of the CS to the start of the first clock pulse.

- google,cros-ec-spi-msg-delay: Some implementations of the EC require some

  additional processing time in order to accept new transactions. If the delay

  between transactions is not long enough the EC may not be able to respond

  properly to subsequent transactions and cause them to hang. This property

  specifies the delay, in usecs, introduced between transactions to account

  for the time required by the EC to get back into a state in which new data

  can be accepted.

Required properties (LPC):

- compatible: "google,cros-ec-lpc"

- reg: List of (IO address, size) pairs defining the interface uses

Optional properties (all):

- google,has-vbc-nvram: Some implementations of the EC include a small

  nvram space used to store verified boot context data. This boolean flag

  is used to specify whether this nvram is present or not.

Example for I2C:

i2c@12ca0000 {

	cros-ec@1e {

		reg = <0x1e>;

		compatible = "google,cros-ec-i2c";

		interrupts = <14 0>;

		interrupt-parent = <&wakeup_eint>;

		wakeup-source;

	};

Example for SPI:

spi@131b0000 {

	ec@0 {

		compatible = "google,cros-ec-spi";

		reg = <0x0>;

		interrupts = <14 0>;

		interrupt-parent = <&wakeup_eint>;

		wakeup-source;

		spi-max-frequency = <5000000>;

		controller-data {

		cs-gpio = <&gpf0 3 4 3 0>;

		samsung,spi-cs;

		samsung,spi-feedback-delay = <2>;

		};

	};

};

Example for LPC is not supplied as it is not yet implemented.

# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)

%YAML 1.2

---

$id: http://devicetree.org/schemas/mfd/google,cros-ec.yaml#

$schema: http://devicetree.org/meta-schemas/core.yaml#

title: ChromeOS Embedded Controller

maintainers:

  - Benson Leung <bleung@chromium.org>

  - Enric Balletbo i Serra <enric.balletbo@collabora.com>

  - Guenter Roeck <groeck@chromium.org>

description:

  Google's ChromeOS EC is a microcontroller which talks to the AP and

  implements various functions such as keyboard and battery charging.

  The EC can be connected through various interfaces (I2C, SPI, and others)

  and the compatible string specifies which interface is being used.

properties:

  compatible:

    oneOf:

      - description:

          For implementations of the EC is connected through I2C.

        const: google,cros-ec-i2c

      - description:

          For implementations of the EC is connected through SPI.

        const: google,cros-ec-spi

      - description:

          For implementations of the EC is connected through RPMSG.

        const: google,cros-ec-rpmsg

  google,cros-ec-spi-pre-delay:

    description:

      This property specifies the delay in usecs between the

      assertion of the CS and the first clock pulse.

    allOf:

      - $ref: /schemas/types.yaml#/definitions/uint32

      - default: 0

      - minimum: 0

  google,cros-ec-spi-msg-delay:

    description:

      This property specifies the delay in usecs between messages.

    allOf:

      - $ref: /schemas/types.yaml#/definitions/uint32

      - default: 0

      - minimum: 0

  google,has-vbc-nvram:

    description:

      Some implementations of the EC include a small nvram space used to

      store verified boot context data. This boolean flag is used to specify

      whether this nvram is present or not.

    type: boolean

  spi-max-frequency:

    description: Maximum SPI frequency of the device in Hz.

  reg:

    maxItems: 1

  interrupts:

    maxItems: 1

required:

  - compatible

if:

  properties:

    compatible:

      contains:

        enum:

          - google,cros-ec-i2c

          - google,cros-ec-rpmsg

then:

  properties:

    google,cros-ec-spi-pre-delay: false

    google,cros-ec-spi-msg-delay: false

    spi-max-frequency: false

additionalProperties: false

examples:

  # Example for I2C

  - |

    #include <dt-bindings/gpio/gpio.h>

    #include <dt-bindings/interrupt-controller/irq.h>

    i2c0 {

        #address-cells = <1>;

        #size-cells = <0>;

        cros-ec@1e {

            compatible = "google,cros-ec-i2c";

            reg = <0x1e>;

            interrupts = <6 0>;

            interrupt-parent = <&gpio0>;

        };

    };

  # Example for SPI

  - |

    #include <dt-bindings/gpio/gpio.h>

    #include <dt-bindings/interrupt-controller/irq.h>

    spi0 {

        #address-cells = <1>;

        #size-cells = <0>;

        cros-ec@0 {

            compatible = "google,cros-ec-spi";

            reg = <0x0>;

            google,cros-ec-spi-msg-delay = <30>;

            google,cros-ec-spi-pre-delay = <10>;

            interrupts = <99 0>;

            interrupt-parent = <&gpio7>;

            spi-max-frequency = <5000000>;

        };

    };

  # Example for RPMSG

  - |

    scp0 {

        cros-ec {

            compatible = "google,cros-ec-rpmsg";

        };

    };

...