Re: [PATCH 4/8] dt-bindings: iio: dfsdm: move to backend framework

Hi Conor,

On 6/18/24 20:10, Conor Dooley wrote:

On Tue, Jun 18, 2024 at 06:08:30PM +0200, Olivier Moysan wrote:

...

Change the DFSDM binding to use the new IIO backend framework, along with the adoption of IIO generic channels. This binding change allows to add scaling support to the DFSDM.

Keep the legacy binding as deprecated for backward compatibility.

The io-backends property is supported only in generic IIO channel binding.

• Channel description with the generic binding (Audio and Analog):

  Properties supersed by generic properties: st,adc-channels: becomes "reg" property in channel node st,adc-channel-names: becomes "label" property in channel node Properties moved to channel child node: st,adc-channel-types, st,adc-channel-clk-src, st,adc-alt-channel

• Analog binding:

  DFSDM filter channel is configured as an IIO backend consumer. Add io-backends property in channel child nodes.

  DFSDM is no more configured as a channel consumer from SD modulator. Use of io-channels in DFSDM node is deprecated.

• Audio binding:

  DFSDM audio DAI is configured as a channel consumer from DFSDM filter. No change compare to legacy.

Signed-off-by: Olivier Moysan olivier.moysan@foss.st.com

.../bindings/iio/adc/st,stm32-dfsdm-adc.yaml | 158 +++++++++++++++++- 1 file changed, 152 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml index c1b1324fa132..dd414bab74c1 100644 --- a/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml @@ -102,9 +102,11 @@ patternProperties: items: minimum: 0 maximum: 7

•    deprecated: true
  
    st,adc-channel-names:
      description: List of single-ended channel names.
  

•    deprecated: true
  
    st,filter-order:
      description: |
  

@@ -118,6 +120,12 @@ patternProperties: "#io-channel-cells": const: 1

•  '#address-cells':
  

•    const: 1
  

•  '#size-cells':
  

•    const: 0
  

•   st,adc-channel-types:
      description: |
        Single-ended channel input type.
  

@@ -128,6 +136,7 @@ patternProperties: items: enum: [ SPI_R, SPI_F, MANCH_R, MANCH_F ] $ref: /schemas/types.yaml#/definitions/non-unique-string-array

•    deprecated: true
  
    st,adc-channel-clk-src:
      description: |
  

@@ -139,6 +148,7 @@ patternProperties: items: enum: [ CLKIN, CLKOUT, CLKOUT_F, CLKOUT_R ] $ref: /schemas/types.yaml#/definitions/non-unique-string-array

•    deprecated: true
  
    st,adc-alt-channel:
      description:
  

@@ -147,6 +157,7 @@ patternProperties: If not set, channel n is connected to SPI input n. If set, channel n is connected to SPI input n + 1. type: boolean

•    deprecated: true
  
    st,filter0-sync:
      description:
  

@@ -165,11 +176,65 @@ patternProperties: - compatible - reg - interrupts

•  - st,adc-channels
  

•  - st,adc-channel-names
    - st,filter-order
    - "#io-channel-cells"
  
  

• patternProperties:

•  "^channel@([0-9]|1[0-9])$":
  

•    type: object
  

•    $ref: adc.yaml
  

•    description: Represents the external channels which are connected to the DFSDM.
  

•    properties:
  

•      reg:
  

•        items:
  

•          minimum: 0
  

•          maximum: 8
  

•      label:
  

•        description:
  

•          Unique name to identify which channel this is.
  

•      st,adc-channel-types:
  

•        description: |
  

•          Single-ended channel input type.
  

•          - "SPI_R": SPI with data on rising edge (default)
  

•          - "SPI_F": SPI with data on falling edge
  

•          - "MANCH_R": manchester codec, rising edge = logic 0, falling edge = logic 1
  

•          - "MANCH_F": manchester codec, rising edge = logic 1, falling edge = logic 0
  

•        items:
  

•          enum: [ SPI_R, SPI_F, MANCH_R, MANCH_F ]
  

•        $ref: /schemas/types.yaml#/definitions/non-unique-string-array
  

Why is this an array? And why is the property plural? Can a channel have more than one type?

You are right. In channel node context, this property is no more an array. It has to be managed as a single string (This is already the case in the driver). I will change the type in binding and the name, to reflect this.

...

•      st,adc-channel-clk-src:
  

•        description: |
  

•          Conversion clock source.
  

•          - "CLKIN": external SPI clock (CLKIN x)
  

•          - "CLKOUT": internal SPI clock (CLKOUT) (default)
  

•          - "CLKOUT_F": internal SPI clock divided by 2 (falling edge).
  

•          - "CLKOUT_R": internal SPI clock divided by 2 (rising edge).
  

•        items:
  

•          enum: [ CLKIN, CLKOUT, CLKOUT_F, CLKOUT_R ]
  

•        $ref: /schemas/types.yaml#/definitions/non-unique-string-array
  

Ditto here, but s/type/clock source/

Same here.

Thanks, Conor.

...

•      st,adc-alt-channel:
  

•        description:
  

•          Must be defined if two sigma delta modulators are
  

•          connected on same SPI input.
  

•          If not set, channel n is connected to SPI input n.
  

•          If set, channel n is connected to SPI input n + 1.
  

•        type: boolean
  

•      io-backends:
  

•        description:
  

•          From common IIO binding.
  

Drop this from the description.

...

Used to pipe external sigma delta

•          modulator or internal ADC backend to DFSDM channel.
  

•    required:
  

•      - reg
  

•    additionalProperties: false
  

• allOf:
    - if:
        properties:
  

@@ -199,9 +264,19 @@ patternProperties: description: From common IIO binding. Used to pipe external sigma delta modulator or internal ADC output to DFSDM channel.

•          deprecated: true
  
  

•      required:
  

•        - io-channels
  

•      if:
  

•        required:
  

•          - st,adc-channels
  

•      then:
  

•        required:
  

•          - io-channels
  

•      patternProperties:
  

•        "^channel@([0-9]|1[0-9])$":
  

•          required:
  

•            - io-backends
  

Why is this here, rather than with reg above? Only some channels require a backend?

The io-backends property is required only when we use st,stm32-dfsdm-adc compatible. In other words, when we are in an analog use case. In this case the channel is a consumer of a backend (typically a sd modulator) In an audio use case (compatible st,stm32-dfsdm-dmic) the backend is not required.

BRs Olivier