Documentation/devicetree/bindings/spi/spi-controller.yaml

Source file repositories/reference/linux-study-clean/Documentation/devicetree/bindings/spi/spi-controller.yaml

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Linux kernel
Corpus path
Documentation/devicetree/bindings/spi/spi-controller.yaml
Extension
.yaml
Size
5864 bytes
Lines
217
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: configuration, schema, or hardware description
Status
atlas-only

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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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

title: SPI Controller Common Properties

maintainers:
  - Mark Brown <broonie@kernel.org>

description: |
  SPI busses can be described with a node for the SPI controller device
  and a set of child nodes for each SPI slave on the bus. The system SPI
  controller may be described for use in SPI master mode or in SPI slave mode,
  but not for both at the same time.

properties:
  $nodename:
    pattern: "^spi(@.*|-([0-9]|[1-9][0-9]+))?$"

  "#address-cells":
    enum: [0, 1]

  "#size-cells":
    const: 0

  cs-gpios:
    description: |
      GPIOs used as chip selects.
      If that property is used, the number of chip selects will be
      increased automatically with max(cs-gpios, hardware chip selects).

      So if, for example, the controller has 4 CS lines, and the
      cs-gpios looks like this
        cs-gpios = <&gpio1 0 0>, <0>, <&gpio1 1 0>, <&gpio1 2 0>;

      Then it should be configured so that num_chipselect = 4, with
      the following mapping
        cs0 : &gpio1 0 0
        cs1 : native
        cs2 : &gpio1 1 0
        cs3 : &gpio1 2 0

      The second flag of a gpio descriptor can be GPIO_ACTIVE_HIGH (0)
      or GPIO_ACTIVE_LOW(1). Legacy device trees often use 0.

      There is a special rule set for combining the second flag of an
      cs-gpio with the optional spi-cs-high flag for SPI slaves.

      Each table entry defines how the CS pin is to be physically
      driven (not considering potential gpio inversions by pinmux):

      device node     | cs-gpio       | CS pin state active | Note
      ================+===============+=====================+=====
      spi-cs-high     | -             | H                   |
      -               | -             | L                   |
      spi-cs-high     | ACTIVE_HIGH   | H                   |
      -               | ACTIVE_HIGH   | L                   | 1
      spi-cs-high     | ACTIVE_LOW    | H                   | 2
      -               | ACTIVE_LOW    | L                   |

      Notes:
      1) Should print a warning about polarity inversion.
         Here it would be wise to avoid and define the gpio as
         ACTIVE_LOW.
      2) Should print a warning about polarity inversion
         because ACTIVE_LOW is overridden by spi-cs-high.
         Should be generally avoided and be replaced by
         spi-cs-high + ACTIVE_HIGH.

Annotation

Implementation Notes