dt-bindings: mailbox : arm,mhuv2: Add bindings

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

%YAML 1.2

---

$id: http://devicetree.org/schemas/mailbox/arm,mhuv2.yaml#

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

title: ARM MHUv2 Mailbox Controller

maintainers:

  - Tushar Khandelwal <tushar.khandelwal@arm.com>

  - Viresh Kumar <viresh.kumar@linaro.org>

description: |

  The Arm Message Handling Unit (MHU) Version 2 is a mailbox controller that has

  between 1 and 124 channel windows (each 32-bit wide) to provide unidirectional

  communication with remote processor(s), where the number of channel windows

  are implementation dependent.

  Given the unidirectional nature of the controller, an MHUv2 mailbox may only

  be written to or read from. If a pair of MHU controllers is implemented

  between two processing elements to provide bidirectional communication, these

  must be specified as two separate mailboxes.

  If the interrupts property is present in device tree node, then its treated as

  a "receiver" mailbox, otherwise a "sender".

  An MHU controller must be specified along with the supported transport

  protocols. The transport protocols determine the method of data transmission

  as well as the number of provided mailbox channels.

  Following are the possible transport protocols.

  - Data-transfer: Each transfer is made of one or more words, using one or more

    channel windows.

  - Doorbell: Each transfer is made up of single bit flag, using any one of the

    bits in a channel window. A channel window can support up to 32 doorbells

    and the entire window shall be used in doorbell protocol.  Optionally, data

    may be transmitted through a shared memory region, wherein the MHU is used

    strictly as an interrupt generation mechanism but that is out of the scope

    of these bindings.

# We need a select here so we don't match all nodes with 'arm,primecell'

select:

  properties:

    compatible:

      contains:

        enum:

          - arm,mhuv2-tx

          - arm,mhuv2-rx

  required:

    - compatible

properties:

  compatible:

    oneOf:

      - description: Sender mode

        items:

          - const: arm,mhuv2-tx

          - const: arm,primecell

      - description: Receiver-mode

        items:

          - const: arm,mhuv2-rx

          - const: arm,primecell

  reg:

    maxItems: 1

  interrupts:

    description: |

      The MHUv2 controller always implements an interrupt in the "receiver"

      mode, while the interrupt in the "sender" mode was not available in the

      version MHUv2.0, but the later versions do have it.

    maxItems: 1

  clocks:

    maxItems: 1

  clock-names:

    maxItems: 1

  arm,mhuv2-protocols:

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

    description: |

      The MHUv2 controller may contain up to 124 channel windows (each 32-bit

      wide). The hardware and the DT bindings allows any combination of those to

      be used for various transport protocols.

      This property allows a platform to describe how these channel windows are

      used in various transport protocols. The entries in this property shall be

      present as an array of tuples, where each tuple describes details about

      one of the transport protocol being implemented over some channel

      window(s).

      The first field of a tuple signifies the transfer protocol, 0 is reserved

      for doorbell protocol, and 1 is reserved for data-transfer protocol.

      Using any other value in the first field of a tuple makes it invalid.

      The second field of a tuple signifies the number of channel windows where

      the protocol would be used and should be set to a non zero value. For

      doorbell protocol this field signifies the number of 32-bit channel

      windows that implement the doorbell protocol. For data-transfer protocol,

      this field signifies the number of 32-bit channel windows that implement

      the data-transfer protocol.

      The total number of channel windows specified here shouldn't be more than

      the ones implemented by the platform, though one can specify lesser number

      of windows here than what the platform implements.

      mhu: mailbox@2b1f0000 {

          ...

          arm,mhuv2-protocols = <0 2>, <1 1>, <1 5>, <1 7>;

      }

      The above example defines the protocols of an ARM MHUv2 mailbox

      controller, where a total of 15 channel windows are used. The first two

      windows are used in doorbell protocol (64 doorbells), followed by 1, 5 and

      7 windows (separately) used in data-transfer protocol.

    minItems: 1

    maxItems: 124

    items:

      items:

        - enum: [ 0, 1 ]

        - minimum: 0

          maximum: 124

  '#mbox-cells':

    description: |

      It is always set to 2. The first argument in the consumers 'mboxes'

      property represents the channel window group, which may be used in

      doorbell, or data-transfer protocol, and the second argument (only

      relevant in doorbell protocol, should be 0 otherwise) represents the

      doorbell number within the 32 bit wide channel window.

      From the example given above for arm,mhuv2-protocols, here is how a client

      node can reference them.

      mboxes = <&mhu 0 5>; // Channel Window Group 0, doorbell 5.

      mboxes = <&mhu 1 7>; // Channel Window Group 1, doorbell 7.

      mboxes = <&mhu 2 0>; // Channel Window Group 2, data transfer protocol with 1 window.

      mboxes = <&mhu 3 0>; // Channel Window Group 3, data transfer protocol with 5 windows.

      mboxes = <&mhu 4 0>; // Channel Window Group 4, data transfer protocol with 7 windows.

    const: 2

if:

  # Interrupt is compulsory for receiver

  properties:

    compatible:

      contains:

        const: arm,mhuv2-rx

then:

  required:

    - interrupts

required:

  - compatible

  - reg

  - '#mbox-cells'

  - arm,mhuv2-protocols

additionalProperties: false

examples:

  # Multiple transport protocols implemented by the mailbox controllers

  - |

    soc {

        #address-cells = <2>;

        #size-cells = <2>;

        mhu_tx: mailbox@2b1f0000 {

            #mbox-cells = <2>;

            compatible = "arm,mhuv2-tx", "arm,primecell";

            reg = <0 0x2b1f0000 0 0x1000>;

            clocks = <&clock 0>;

            clock-names = "apb_pclk";

            interrupts = <0 45 4>;

            arm,mhuv2-protocols = <1 5>, <1 2>, <1 5>, <1 7>, <0 2>;

        };

        mhu_rx: mailbox@2b1f1000 {

            #mbox-cells = <2>;

            compatible = "arm,mhuv2-rx", "arm,primecell";

            reg = <0 0x2b1f1000 0 0x1000>;

            clocks = <&clock 0>;

            clock-names = "apb_pclk";

            interrupts = <0 46 4>;

            arm,mhuv2-protocols = <1 1>, <1 7>, <0 2>;

        };

        mhu_client: scb@2e000000 {

            compatible = "fujitsu,mb86s70-scb-1.0";

            reg = <0 0x2e000000 0 0x4000>;

            mboxes =

                     //data-transfer protocol with 5 windows, mhu-tx

                     <&mhu_tx 2 0>,

                     //data-transfer protocol with 7 windows, mhu-tx

                     <&mhu_tx 3 0>,

                     //doorbell protocol channel 4, doorbell 27, mhu-tx

                     <&mhu_tx 4 27>,

                     //data-transfer protocol with 1 window, mhu-rx

                     <&mhu_rx 0 0>;

        };

    };