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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 Generic Binding
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:
$nodename:
pattern: "^spi(@.*|-[0-9a-f])*$"
"#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.
num-cs:
$ref: /schemas/types.yaml#/definitions/uint32
description:
Total number of chip selects.
spi-slave:
$ref: /schemas/types.yaml#/definitions/flag
description:
The SPI controller acts as a slave, instead of a master.
allOf:
- if:
not:
required:
- spi-slave
then:
properties:
"#address-cells":
const: 1
else:
properties:
"#address-cells":
const: 0
patternProperties:
"^slave$":
type: object
properties:
compatible:
description:
Compatible of the SPI device.
required:
- compatible
"^.*@[0-9a-f]+$":
type: object
properties:
compatible:
description:
Compatible of the SPI device.
reg:
minimum: 0
maximum: 256
description:
Chip select used by the device.
spi-3wire:
$ref: /schemas/types.yaml#/definitions/flag
description:
The device requires 3-wire mode.
spi-cpha:
$ref: /schemas/types.yaml#/definitions/flag
description:
The device requires shifted clock phase (CPHA) mode.
spi-cpol:
$ref: /schemas/types.yaml#/definitions/flag
description:
The device requires inverse clock polarity (CPOL) mode.
spi-cs-high:
$ref: /schemas/types.yaml#/definitions/flag
description:
The device requires the chip select active high.
spi-lsb-first:
$ref: /schemas/types.yaml#/definitions/flag
description:
The device requires the LSB first mode.
spi-max-frequency:
$ref: /schemas/types.yaml#/definitions/uint32
description:
Maximum SPI clocking speed of the device in Hz.
spi-rx-bus-width:
description:
Bus width to the SPI bus used for read transfers.
If 0 is provided, then no RX will be possible on this device.
$ref: /schemas/types.yaml#/definitions/uint32
enum: [0, 1, 2, 4, 8]
default: 1
spi-rx-delay-us:
description:
Delay, in microseconds, after a read transfer.
spi-tx-bus-width:
description:
Bus width to the SPI bus used for write transfers.
If 0 is provided, then no TX will be possible on this device.
$ref: /schemas/types.yaml#/definitions/uint32
enum: [0, 1, 2, 4, 8]
default: 1
spi-tx-delay-us:
description:
Delay, in microseconds, after a write transfer.
required:
- compatible
- reg
additionalProperties: true
examples:
- |
spi@80010000 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "fsl,imx28-spi";
reg = <0x80010000 0x2000>;
interrupts = <96>;
dmas = <&dma_apbh 0>;
dma-names = "rx-tx";
display@0 {
compatible = "lg,lg4573";
spi-max-frequency = <1000000>;
reg = <0>;
};
sensor@1 {
compatible = "bosch,bme680";
spi-max-frequency = <100000>;
reg = <1>;
};
};
|
