linux/Documentation/devicetree/bindings/memory-controllers/ddr/jedec,sdram-channel.yaml

# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/memory-controllers/ddr/jedec,sdram-channel.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: SDRAM channel with chip/rank topology description

description:
  A memory channel of SDRAM memory like DDR SDRAM or LPDDR SDRAM is a completely
  independent set of pins (DQ, CA, CS, CK, etc.) that connect one or more memory
  chips to a host system. The main purpose of this node is to overall memory
  topology of the system, including the amount of individual memory chips and
  the ranks per chip.

maintainers:
  - Julius Werner <jwerner@chromium.org>

properties:
  $nodename:
    pattern: "sdram-channel-[0-9]+$"

  compatible:
    enum:
      - jedec,ddr4-channel
      - jedec,lpddr2-channel
      - jedec,lpddr3-channel
      - jedec,lpddr4-channel
      - jedec,lpddr5-channel

  io-width:
    description:
      The number of DQ pins in the channel. If this number is different
      from (a multiple of) the io-width of the SDRAM chip, that means that
      multiple instances of that type of chip are wired in parallel on this
      channel (with the channel's DQ pins split up between the different
      chips, and the CA, CS, etc. pins of the different chips all shorted
      together).  This means that the total physical memory controlled by a
      channel is equal to the sum of the densities of each rank on the
      connected SDRAM chip, times the io-width of the channel divided by
      the io-width of the SDRAM chip.
    enum:
      - 8
      - 16
      - 32
      - 64
      - 128

  "#address-cells":
    const: 1

  "#size-cells":
    const: 0

patternProperties:
  "^rank@[0-9]+$":
    type: object
    description:
      Each physical SDRAM chip may have one or more ranks. Ranks are
      internal but fully independent sub-units of the chip. Each SDRAM bus
      transaction on the channel targets exactly one rank, based on the
      state of the CS pins. Different ranks may have different densities and
      timing requirements.
    required:
      - reg

allOf:
  - if:
      properties:
        compatible:
          contains:
            const: jedec,ddr4-channel
    then:
      patternProperties:
        "^rank@[0-9]+$":
          $ref: /schemas/memory-controllers/ddr/jedec,ddr4.yaml#
  - if:
      properties:
        compatible:
          contains:
            const: jedec,lpddr2-channel
    then:
      patternProperties:
        "^rank@[0-9]+$":
          $ref: /schemas/memory-controllers/ddr/jedec,lpddr2.yaml#
  - if:
      properties:
        compatible:
          contains:
            const: jedec,lpddr3-channel
    then:
      patternProperties:
        "^rank@[0-9]+$":
          $ref: /schemas/memory-controllers/ddr/jedec,lpddr3.yaml#
  - if:
      properties:
        compatible:
          contains:
            const: jedec,lpddr4-channel
    then:
      patternProperties:
        "^rank@[0-9]+$":
          $ref: /schemas/memory-controllers/ddr/jedec,lpddr4.yaml#
  - if:
      properties:
        compatible:
          contains:
            const: jedec,lpddr5-channel
    then:
      patternProperties:
        "^rank@[0-9]+$":
          $ref: /schemas/memory-controllers/ddr/jedec,lpddr5.yaml#

required:
  - compatible
  - io-width
  - "#address-cells"
  - "#size-cells"

additionalProperties: false

examples:
  - |
    sdram-channel-0 {
      #address-cells = <1>;
      #size-cells = <0>;
      compatible = "jedec,lpddr3-channel";
      io-width = <32>;

      rank@0 {
        compatible = "lpddr3-ff,0100", "jedec,lpddr3";
        reg = <0>;
        density = <8192>;
        io-width = <16>;
        revision-id = <1 0>;
      };
    };

    sdram-channel-1 {
      #address-cells = <1>;
      #size-cells = <0>;
      compatible = "jedec,lpddr4-channel";
      io-width = <32>;

      rank@0 {
        compatible = "lpddr4-05,0301", "jedec,lpddr4";
        reg = <0>;
        density = <4096>;
        io-width = <32>;
        revision-id = <3 1>;
      };

      rank@1 {
        compatible = "lpddr4-05,0301", "jedec,lpddr4";
        reg = <1>;
        density = <2048>;
        io-width = <32>;
        revision-id = <3 1>;
      };
    };