linux/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

  cs-gpios:
    description:
      Array of chip-select available to the controller. The first
      entries are a 1:1 mapping of the available chip-select on the
      NAND controller (even if they are not used). As many additional
      chip-select as needed may follow and should be phandles of GPIO
      lines. 'reg' entries of the NAND chip subnodes become indexes of
      this array when this property is present.
    minItems: 1
    maxItems: 8

patternProperties:
  "^nand@[a-f0-9]$":
    type: object
    $ref: "nand-chip.yaml#"

    properties:
      reg:
        description:
          Contains the chip-select IDs.

      nand-ecc-placement:
        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.
        $ref: /schemas/types.yaml#/definitions/string
        enum: [ oob, interleaved ]

      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:
        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.
        $ref: /schemas/types.yaml#/definitions/flag

      nand-ecc-maximize:
        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.
        $ref: /schemas/types.yaml#/definitions/flag

      nand-is-boot-medium:
        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.
        $ref: /schemas/types.yaml#/definitions/flag

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

      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.

      wp-gpios:
        description:
          Contains one GPIO descriptor for the Write Protect pin.
          Active state refers to the NAND Write Protect state and should be
          set to GPIOD_ACTIVE_LOW unless the signal is inverted.
        maxItems: 1

    required:
      - reg

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

additionalProperties: true

examples:
  - |
    nand-controller {
      #address-cells = <1>;
      #size-cells = <0>;
      cs-gpios = <0>, <&gpioA 1>; /* A single native CS is available */

      /* controller specific properties */

      nand@0 {
        reg = <0>; /* Native CS */
        /* NAND chip specific properties */
      };

      nand@1 {
        reg = <1>; /* GPIO CS */
      };
    };