leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

spi: dt-bindings: add schema listing peripheral-specific properties

Browse Source 
Many SPI controllers need to add properties to peripheral devices. This
could be the delay in clock or data lines, etc. These properties are
controller specific but need to be defined in the peripheral node
because they are per-peripheral and there can be multiple peripherals
attached to a controller.

If these properties are not added to the peripheral binding, then the
dtbs check emits a warning. But these properties do not make much sense
in the peripheral binding because they are controller-specific and they
will just pollute every peripheral binding. So this binding is added to
collect all such properties from all such controllers. Peripheral
bindings should simply refer to this binding and they should be rid of
the warnings.

There are some limitations with this approach. Firstly, there is no way
to specify required properties. The schema contains properties for all
controllers and there is no way to know which controller is being used.
Secondly, there is no way to restrict additional properties. Since this
schema will be used with an allOf operator, additionalProperties needs
to be true. In addition, the peripheral schema will have to set
unevaluatedProperties: false.

Despite these limitations, this appears to be the best solution to this
problem that doesn't involve modifying existing tools or schema specs.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211109181911.2251-2-p.yadav@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Pratyush Yadav 2021-11-09 23:49:09 +05:30 committed by Mark Brown
parent 8393961c53
commit 8762b07c95
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
2 changed files with 89 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
Documentation/devicetree/bindings/spi/spi-controller.yaml
View File

@ -94,73 +94,8 @@ patternProperties:
"^.*@[0-9a-f]+$":
type: object
properties:
compatible:
description:
Compatible of the SPI device.
reg:
minItems: 1
maxItems: 256
items:
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.
allOf:
- $ref: spi-peripheral-props.yaml
required:
- compatible

87
Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml Normal file
View File

@ -0,0 +1,87 @@
# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/spi/spi-peripheral-props.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#
title: Peripheral-specific properties for a SPI bus.
description:
Many SPI controllers need to add properties to peripheral devices. They could
be common properties like spi-max-frequency, spi-cpha, etc. or they could be
controller specific like delay in clock or data lines, etc. These properties
need to be defined in the peripheral node because they are per-peripheral and
there can be multiple peripherals attached to a controller. All those
properties are listed here. The controller specific properties should go in
their own separate schema that should be referenced from here.
maintainers:
- Pratyush Yadav <p.yadav@ti.com>
properties:
reg:
minItems: 1
maxItems: 256
items:
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.
# The controller specific properties go here.
additionalProperties: true