FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/mailbox/arm,mhu.yaml

     # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
     %YAML 1.2
     ---
     $id: http://devicetree.org/schemas/mailbox/arm,mhu.yaml#
     $schema: http://devicetree.org/meta-schemas/core.yaml#
     
     title: ARM MHU Mailbox Controller
     
     maintainers:
      - Jassi Brar <jaswinder.singh@linaro.org>
    
    description: |
      The ARM's Message-Handling-Unit (MHU) is a mailbox controller that has 3
      independent channels/links to communicate with remote processor(s).  MHU links
      are hardwired on a platform. A link raises interrupt for any received data.
      However, there is no specified way of knowing if the sent data has been read
      by the remote. This driver assumes the sender polls STAT register and the
      remote clears it after having read the data.  The last channel is specified to
      be a 'Secure' resource, hence can't be used by Linux running NS.
    
      The MHU hardware also allows operations in doorbell mode. The MHU drives the
      interrupt signal using a 32-bit register, with all 32-bits logically ORed
      together. It provides a set of registers to enable software to set, clear and
      check the status of each of the bits of this register independently. The use
      of 32 bits per interrupt line enables software to provide more information
      about the source of the interrupt. For example, each bit of the register can
      be associated with a type of event that can contribute to raising the
      interrupt. Each of the 32-bits can be used as "doorbell" to alert the remote
      processor.
    
    # We need a select here so we don't match all nodes with 'arm,primecell'
    select:
      properties:
        compatible:
          contains:
            enum:
              - arm,mhu
              - arm,mhu-doorbell
      required:
        - compatible
    
    properties:
      compatible:
        oneOf:
          - description: Data transfer mode
            items:
              - const: arm,mhu
              - const: arm,primecell
    
          - description: Doorbell mode
            items:
              - const: arm,mhu-doorbell
              - const: arm,primecell
    
    
      reg:
        maxItems: 1
    
      interrupts:
        minItems: 2
        items:
          - description: low-priority non-secure
          - description: high-priority non-secure
          - description: Secure
    
      clocks:
        maxItems: 1
    
      clock-names:
        items:
          - const: apb_pclk
    
      '#mbox-cells':
        description: |
          Set to 1 in data transfer mode and represents index of the channel.
          Set to 2 in doorbell mode and represents index of the channel and doorbell
          number.
        enum: [ 1, 2 ]
    
    required:
      - compatible
      - reg
      - interrupts
      - '#mbox-cells'
    
    additionalProperties: false
    
    examples:
      # Data transfer mode.
      - |
        soc {
            #address-cells = <2>;
            #size-cells = <2>;
    
            mhuA: mailbox@2b1f0000 {
                #mbox-cells = <1>;
                compatible = "arm,mhu", "arm,primecell";
                reg = <0 0x2b1f0000 0 0x1000>;
                interrupts = <0 36 4>, /* LP-NonSecure */
                            <0 35 4>, /* HP-NonSecure */
                            <0 37 4>; /* Secure */
               clocks = <&clock 0 2 1>;
               clock-names = "apb_pclk";
           };
       };
   
       firmware {
           scpi {
               compatible = "arm,scpi";
               mboxes = <&mhuA 1>; /* HP-NonSecure */
               shmem = <&cpu_scp_hpri>; /* HP-NonSecure */
   
               scpi_devpd: power-controller {
                   compatible = "arm,scpi-power-domains";
                   num-domains = <2>;
                   #power-domain-cells = <1>;
               };
           };
       };
   
     # Doorbell mode.
     - |
       soc {
           #address-cells = <2>;
           #size-cells = <2>;
   
           mhuB: mailbox@2b2f0000 {
               #mbox-cells = <2>;
               compatible = "arm,mhu-doorbell", "arm,primecell";
               reg = <0 0x2b2f0000 0 0x1000>;
               interrupts = <0 36 4>, /* LP-NonSecure */
                            <0 35 4>, /* HP-NonSecure */
                            <0 37 4>; /* Secure */
               clocks = <&clock 0 2 1>;
               clock-names = "apb_pclk";
           };
       };
   
       firmware {
           scmi {
               compatible = "arm,scmi";
               mboxes = <&mhuB 0 0>, /* LP-NonSecure, 1st doorbell */
                        <&mhuB 0 1>; /* LP-NonSecure, 2nd doorbell */
               mbox-names = "tx", "rx";
               shmem = <&cpu_scp_lpri0>,
                       <&cpu_scp_lpri1>;
   
               #address-cells = <1>;
               #size-cells = <0>;
   
               scmi_devpd: protocol@11 {
                   reg = <0x11>;
                   #power-domain-cells = <1>;
               };
   
               scmi_dvfs: protocol@13 {
                   reg = <0x13>;
                   #clock-cells = <1>;
   
                   mboxes = <&mhuB 1 2>, /* HP-NonSecure, 3rd doorbell */
                            <&mhuB 1 3>; /* HP-NonSecure, 4th doorbell */
                   mbox-names = "tx", "rx";
                   shmem = <&cpu_scp_hpri0>,
                           <&cpu_scp_hpri1>;
               };
           };
       };
   
   ...

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