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]$":
    properties:
      reg:
        description:
          Contains the native Ready/Busy IDs.

      nand-ecc-mode:
        allOf:
          - $ref: /schemas/types.yaml#/definitions/string
          - enum: [ none, soft, hw, hw_syndrome, hw_oob_first, on-die ]
        description:
          Desired ECC engine, either hardware (most of the time
          embedded in the NAND controller) or software correction
          (Linux will handle the calculations). soft_bch is deprecated
          and should be replaced by soft and nand-ecc-algo.

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

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

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

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

      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.

    required:
      - reg

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

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

      /* controller specific properties */

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

        /* controller specific properties */
      };
    };