Documentation/devicetree/bindings/mfd/syscon-common.yaml

# SPDX-License-Identifier: GPL-2.0
%YAML 1.2
---
$id: http://devicetree.org/schemas/mfd/syscon-common.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: System Controller Registers R/W Common Properties

description:
  System controller node represents a register region containing a set
  of miscellaneous registers. The registers are not cohesive enough to
  represent as any specific type of device. The typical use-case is
  for some other node's driver, or platform-specific code, to acquire
  a reference to the syscon node (e.g. by phandle, node path, or
  search using a specific compatible value), interrogate the node (or
  associated OS driver) to determine the location of the registers,
  and access the registers directly.

maintainers:
  - Lee Jones <lee@kernel.org>

select:
  properties:
    compatible:
      contains:
        const: syscon

  required:
    - compatible

properties:
  compatible:
    contains:
      const: syscon
    # Always require a specific compatible for syscon
    minItems: 2
    maxItems: 5  # Should be enough

  reg-io-width:
    description:
      The size (in bytes) of the IO accesses that should be performed
      on the device.
    enum: [1, 2, 4, 8]

required:
  - compatible
  - reg

allOf:
  - if:
      properties:
        compatible:
          contains:
            const: simple-mfd
    then:
      # Always require a specific compatible for syscon with simple-mfd
      properties:
        compatible:
          minItems: 3
          maxItems: 5

  - if:
      properties:
        compatible:
          contains:
            const: simple-bus
    then:
      # simple-bus conflicts with syscon - if a device is a system controller
      # with miscellaneous registers, then it has at least one dedicated
      # function thus it is not a simple bus. Allow existing exceptions.
      if:
        properties:
          compatible:
            not:
              contains:
                # This list CANNOT grow
                enum:
                  - cznic,turris1x-cpld
                  - img,pistachio-cr-periph
                  - ti,am3352-scm-conf
                  - ti,am4372-scm-conf
                  - ti,dm814-scm-conf
                  - ti,dm8168-scm-conf
                  - ti,dra7-scm-conf
                  - ti,omap2-scm-conf
                  - ti,omap3-scm-conf
                  - ti,omap4-sysc-padconf-global
                  - ti,omap5-scm-wkup-conf
                  - ti,omap5-sysc-padconf-global
      then:
        required:
          - incorrect-usage-of-simple-bus-and-syscon

additionalProperties: true

examples:
  - |
    syscon: syscon@1c00000 {
        compatible = "allwinner,sun8i-h3-system-controller", "syscon";
        reg = <0x01c00000 0x1000>;
    };
...