Documentation/devicetree/bindings/mtd/nand-controller.yaml

# SPDX-License-Identifier: GPL-2.0
%YAML 1.2
---
$id: http://devicetree.org/schemas/mtd/nand-controller.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: NAND Chip and NAND Controller Generic Binding

maintainers:
  - Miquel Raynal <miquel.raynal@bootlin.com>
  - Richard Weinberger <richard@nod.at>

description: |
  The NAND controller should be represented with its own DT node, and
  all NAND chips attached to this controller should be defined as
  children nodes of the NAND controller. This representation should be
  enforced even for simple controllers supporting only one chip.

  The ECC strength and ECC step size properties define the user
  desires in terms of correction capability of a controller. Together,
  they request the ECC engine to correct {strength} bit errors per
  {size} bytes.

  The interpretation of these parameters is implementation-defined, so
  not all implementations must support all possible
  combinations. However, implementations are encouraged to further
  specify the value(s) they support.

properties:
  $nodename:
    pattern: "^nand-controller(@.*)?"

  "#address-cells":
    const: 1

  "#size-cells":
    const: 0

  ranges: true

patternProperties:
  "^nand@[a-f0-9]$":
    type: object
    properties:
      reg:
        description:
          Contains the native Ready/Busy IDs.

      nand-ecc-engine:
        allOf:
          - $ref: /schemas/types.yaml#/definitions/phandle
        description: |
          A phandle on the hardware ECC engine if any. There are
          basically three possibilities:
          1/ The ECC engine is part of the NAND controller, in this
          case the phandle should reference the parent node.
          2/ The ECC engine is part of the NAND part (on-die), in this
          case the phandle should reference the node itself.
          3/ The ECC engine is external, in this case the phandle should
          reference the specific ECC engine node.

      nand-use-soft-ecc-engine:
        type: boolean
        description: Use a software ECC engine.

      nand-no-ecc-engine:
        type: boolean
        description: Do not use any ECC correction.

      nand-ecc-placement:
        allOf:
          - $ref: /schemas/types.yaml#/definitions/string
          - enum: [ oob, interleaved ]
        description:
          Location of the ECC bytes. This location is unknown by default
          but can be explicitly set to "oob", if all ECC bytes are
          known to be stored in the OOB area, or "interleaved" if ECC
          bytes will be interleaved with regular data in the main area.

      nand-ecc-algo:
        description:
          Desired ECC algorithm.
        $ref: /schemas/types.yaml#/definitions/string
        enum: [hamming, bch, rs]

      nand-bus-width:
        description:
          Bus width to the NAND chip
        $ref: /schemas/types.yaml#/definitions/uint32
        enum: [8, 16]
        default: 8

      nand-on-flash-bbt:
        $ref: /schemas/types.yaml#/definitions/flag
        description:
          With this property, the OS will search the device for a Bad
          Block Table (BBT). If not found, it will create one, reserve
          a few blocks at the end of the device to store it and update
          it as the device ages. Otherwise, the out-of-band area of a
          few pages of all the blocks will be scanned at boot time to
          find Bad Block Markers (BBM). These markers will help to
          build a volatile BBT in RAM.

      nand-ecc-strength:
        description:
          Maximum number of bits that can be corrected per ECC step.
        $ref: /schemas/types.yaml#/definitions/uint32
        minimum: 1

      nand-ecc-step-size:
        description:
          Number of data bytes covered by a single ECC step.
        $ref: /schemas/types.yaml#/definitions/uint32
        minimum: 1

      nand-ecc-maximize:
        $ref: /schemas/types.yaml#/definitions/flag
        description:
          Whether or not the ECC strength should be maximized. The
          maximum ECC strength is both controller and chip
          dependent. The ECC engine has to select the ECC config
          providing the best strength and taking the OOB area size
          constraint into account. This is particularly useful when
          only the in-band area is used by the upper layers, and you
          want to make your NAND as reliable as possible.

      nand-is-boot-medium:
        $ref: /schemas/types.yaml#/definitions/flag
        description:
          Whether or not the NAND chip is a boot medium. Drivers might
          use this information to select ECC algorithms supported by
          the boot ROM or similar restrictions.

      nand-rb:
        $ref: /schemas/types.yaml#/definitions/uint32-array
        description:
          Contains the native Ready/Busy IDs.

      rb-gpios:
        description:
          Contains one or more GPIO descriptor (the numper of descriptor
          depends on the number of R/B pins exposed by the flash) for the
          Ready/Busy pins. Active state refers to the NAND ready state and
          should be set to GPIOD_ACTIVE_HIGH unless the signal is inverted.

    required:
      - reg

required:
  - "#address-cells"
  - "#size-cells"

additionalProperties: true

examples:
  - |
    nand-controller {
      #address-cells = <1>;
      #size-cells = <0>;

      /* controller specific properties */

      nand@0 {
        reg = <0>;
        nand-use-soft-ecc-engine;
        nand-ecc-algo = "bch";

        /* controller specific properties */
      };
    };