[PATCH 0/8] iio: adc: dfsdm: add scaling support

[PATCH 0/8] iio: adc: dfsdm: add scaling support

[Olivier Moysan]

The aim of this serie is to add scaling support to STM32 DFSDM
peripheral in the analog context.

The DFSDM currently operates as a consumer of IIO channels
provided by a generic SD modulator. As previously discussed in RFC [1],
this topology is not suitable for implementing scaling.

This series brings the integration of the DFSDM driver with the new 
IIO backend framework [2], enabling the DFSDM IIO device to offer 
scaling feature based on reference voltage data obtained from the
IIO SD modulator backend. This generic SD modulator backend takes the
place of the former SD modulator, used with legacy implementation.

The DFSDM driver has been updated to adopt the generic ADC channel
binding [3]. The reasons for this include:
- Reducing the use of proprietary properties
- Simplifying the coexistence of legacy and new backend bindings
- Prepare the support of the MDF peripheral on STM32MP25 SoC

Backward compatibility is maintained through legacy support.

This series extends the backend framework with the following APIs 
(which may need further refinement):
- read_raw:
	This API is intented to retrieve the voltage information from the
	backend. It is based on IIO read_raw API, but maybe we need
	a more specialized API here.
- iio_backend_disable / iio_backend_enable:
	backend enable/disable to be used for PM management
- devm_iio_backend_subnode_get
	Intended for parsing DT subnodes to allow generic channel binding
	support, as generic channel DT nodes are not populated as devices.
	Ideally, a single API would be better, but I could not 
	identify a suitable alternative that doesn't affect the existing API
	(devm_iio_backend_get).

[1]: https://lore.kernel.org/lkml/20200204101008.11411-1-olivier.moysan@st.com/
[2]: https://lore.kernel.org/all/20240206-iio-backend-v9-0-df66d159c000@analog.com/
[3]: devicetree/bindings/iio/adc/adc.yaml

Olivier Moysan (8):
  iio: add read raw service to iio backend framework
  iio: add enable and disable services to iio backend framework
  iio: add child nodes support in iio backend framework
  dt-bindings: iio: dfsdm: move to backend framework
  dt-bindings: iio: add sigma delta modulator backend
  iio: adc: stm32-dfsdm: adopt generic channels bindings
  iio: add sd modulator generic iio backend
  iio: adc: stm32-dfsdm: add scaling support to dfsdm

 .../iio/adc/sd-modulator-backend.yaml         |  43 +++
 .../bindings/iio/adc/st,stm32-dfsdm-adc.yaml  | 158 ++++++++-
 drivers/iio/adc/Kconfig                       |  11 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/sd_adc_backend.c              | 110 +++++++
 drivers/iio/adc/stm32-dfsdm-adc.c             | 302 +++++++++++++++---
 drivers/iio/industrialio-backend.c            |  90 +++++-
 include/linux/iio/backend.h                   |   7 +
 8 files changed, 664 insertions(+), 58 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
 create mode 100644 drivers/iio/adc/sd_adc_backend.c


base-commit: 7db8a847f98caae68c70bdab9ba92d1af38e5656
-- 
2.25.1

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

[Olivier Moysan]

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
+
+          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
+
+          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. 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
 
       - if:
           properties:
@@ -294,7 +369,77 @@ examples:
       #address-cells = <1>;
       #size-cells = <0>;
 
+      // Example 1: Audio use case with generic binding
       dfsdm0: filter@0 {
+        compatible = "st,stm32-dfsdm-dmic";
+        reg = <0>;
+        interrupts = <GIC_SPI 110 IRQ_TYPE_LEVEL_HIGH>;
+        dmas = <&dmamux1 101 0x400 0x01>;
+        dma-names = "rx";
+        #io-channel-cells = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        st,filter-order = <5>;
+
+        channel@1 {
+          reg = <1>;
+          label = "dmic0";
+          st,adc-channel-types = "SPI_R";
+          st,adc-channel-clk-src = "CLKOUT";
+          st,adc-alt-channel;
+        };
+
+        asoc_pdm0: dfsdm-dai {
+          compatible = "st,stm32h7-dfsdm-dai";
+          #sound-dai-cells = <0>;
+          io-channels = <&dfsdm0 0>;
+        };
+      };
+
+      // Example 1: Analog use case with generic binding
+      dfsdm1: filter@1 {
+        compatible = "st,stm32-dfsdm-adc";
+        reg = <1>;
+        interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
+        dmas = <&dmamux1 102 0x400 0x01>;
+        dma-names = "rx";
+        st,filter-order = <1>;
+        #io-channel-cells = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        channel@2 {
+          reg = <2>;
+          label = "in2";
+          st,adc-channel-types = "SPI_F";
+          st,adc-channel-clk-src = "CLKOUT";
+          st,adc-alt-channel;
+          io-backends = <&sd_adc2>;
+        };
+
+        channel@3 {
+          reg = <3>;
+          label = "in3";
+          st,adc-channel-types = "SPI_R";
+          st,adc-channel-clk-src = "CLKOUT";
+          io-backends = <&sd_adc3>;
+        };
+      };
+    };
+
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/stm32mp1-clks.h>
+    dfsdm_2: dfsdm@4400d000 {
+      compatible = "st,stm32mp1-dfsdm";
+      reg = <0x4400d000 0x800>;
+      clocks = <&rcc DFSDM_K>, <&rcc ADFSDM_K>;
+      clock-names = "dfsdm", "audio";
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      // Example 3: Audio use case with legacy binding
+      dfsdm0_2: filter@0 {
         compatible = "st,stm32-dfsdm-dmic";
         reg = <0>;
         interrupts = <GIC_SPI 110 IRQ_TYPE_LEVEL_HIGH>;
@@ -307,14 +452,15 @@ examples:
         st,adc-channel-clk-src = "CLKOUT";
         st,filter-order = <5>;
 
-        asoc_pdm0: dfsdm-dai {
+        asoc_pdm0_2: dfsdm-dai {
           compatible = "st,stm32h7-dfsdm-dai";
           #sound-dai-cells = <0>;
           io-channels = <&dfsdm0 0>;
         };
       };
 
-      dfsdm_pdm1: filter@1 {
+      // Example 3: Analog use case with legacy binding
+      dfsdm1_2: filter@1 {
         compatible = "st,stm32-dfsdm-adc";
         reg = <1>;
         interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
-- 
2.25.1

[PATCH 5/8] dt-bindings: iio: add sigma delta modulator backend

[Olivier Moysan]

Add documentation of device tree bindings to support
sigma delta modulator backend in IIO framework.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 .../iio/adc/sd-modulator-backend.yaml         | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml b/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
new file mode 100644
index 000000000000..b0fa71b75cd0
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/sd-modulator-backend.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sigma delta modulator backend
+
+maintainers:
+  - Olivier Moysan <olivier.moysan@foss.st.com>
+
+properties:
+  compatible:
+    description: |
+      "sd-backend" can be used as a generic SD modulator backend,
+      if the modulator is not specified in the compatible list.
+    enum:
+      - sd-backend
+      - ads1201
+
+  '#io-backend-cells':
+    const: 0
+
+  reg:
+    maxItems: 1
+
+  vref-supply:
+    description: Phandle to the vref input analog reference voltage.
+
+required:
+  - compatible
+  - '#io-backend-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    ads1201: adc {
+      compatible = "sd-backend";
+      #io-backend-cells = <0>;
+    };
+
+...
-- 
2.25.1

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

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 6722 bytes --]

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?

> +
> +          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/

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?

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Re: [PATCH 5/8] dt-bindings: iio: add sigma delta modulator backend

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 2224 bytes --]

On Tue, Jun 18, 2024 at 06:08:31PM +0200, Olivier Moysan wrote:
> Add documentation of device tree bindings to support
> sigma delta modulator backend in IIO framework.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  .../iio/adc/sd-modulator-backend.yaml         | 43 +++++++++++++++++++
>  1 file changed, 43 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml b/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
> new file mode 100644
> index 000000000000..b0fa71b75cd0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
> @@ -0,0 +1,43 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/sd-modulator-backend.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Sigma delta modulator backend
> +
> +maintainers:
> +  - Olivier Moysan <olivier.moysan@foss.st.com>
> +
> +properties:
> +  compatible:
> +    description: |
> +      "sd-backend" can be used as a generic SD modulator backend,
> +      if the modulator is not specified in the compatible list.
> +    enum:
> +      - sd-backend

I'd rather not have a generic compatible like this. Something generic as
a fallback for the driver to binding against I would be fine with, but
not something that avoids people documenting their devices.

Also, I think "backend" should be dropped from the
filename/title/descriptions, the ads1201 is "just" an delta-sigma
modulator.:wq

> +      - ads1201

Missing vendor prefix.

Thanks,
Conor.


> +
> +  '#io-backend-cells':
> +    const: 0
> +
> +  reg:
> +    maxItems: 1
> +
> +  vref-supply:
> +    description: Phandle to the vref input analog reference voltage.
> +
> +required:
> +  - compatible
> +  - '#io-backend-cells'
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    ads1201: adc {
> +      compatible = "sd-backend";
> +      #io-backend-cells = <0>;
> +    };
> +
> +...
> -- 
> 2.25.1
> 

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

[Olivier MOYSAN]

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

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

[Conor Dooley]

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On Thu, Jun 20, 2024 at 10:03:44AM +0200, Olivier MOYSAN wrote:
> On 6/18/24 20:10, Conor Dooley wrote:
> > On Tue, Jun 18, 2024 at 06:08:30PM +0200, Olivier Moysan wrote:
> > >       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.

Ahh, I think the hunks and indent confused me here. What you're doing is
making io-backends required based on the compatible, but what I thought
you were doing was trying to make io-backends required in channels if
st,adc-channels was set.

Thanks for the explanation,
Conor.

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

[Jonathan Cameron]

On Tue, 18 Jun 2024 18:08:30 +0200
Olivier Moysan <olivier.moysan@foss.st.com> 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:
superseded

>     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>

Re: [PATCH 5/8] dt-bindings: iio: add sigma delta modulator backend

[Olivier MOYSAN]

Hi Conor,

On 6/18/24 20:13, Conor Dooley wrote:
> On Tue, Jun 18, 2024 at 06:08:31PM +0200, Olivier Moysan wrote:
>> Add documentation of device tree bindings to support
>> sigma delta modulator backend in IIO framework.
>>
>> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
>> ---
>>   .../iio/adc/sd-modulator-backend.yaml         | 43 +++++++++++++++++++
>>   1 file changed, 43 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml b/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
>> new file mode 100644
>> index 000000000000..b0fa71b75cd0
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/sd-modulator-backend.yaml
>> @@ -0,0 +1,43 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/adc/sd-modulator-backend.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Sigma delta modulator backend
>> +
>> +maintainers:
>> +  - Olivier Moysan <olivier.moysan@foss.st.com>
>> +
>> +properties:
>> +  compatible:
>> +    description: |
>> +      "sd-backend" can be used as a generic SD modulator backend,
>> +      if the modulator is not specified in the compatible list.
>> +    enum:
>> +      - sd-backend
> 
> I'd rather not have a generic compatible like this. Something generic as
> a fallback for the driver to binding against I would be fine with, but
> not something that avoids people documenting their devices.
> 

This binding was modeled on the following binding
Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
But, I understand that we need to encourage people to use a real 
compatible. So, I will remove this generic compatible from the binding 
in v2.

> Also, I think "backend" should be dropped from the
> filename/title/descriptions, the ads1201 is "just" an delta-sigma
> modulator.:wq
> 

There is already a generic sigma delta modulator driver: 
"sd_adc_modulator.c"
This driver follows a different approach, as it registers an IIO device. 
It has to be kept for backward compatibility.
The current patch introduces a new sigma delta modulator generic driver
based on the new IIO backend framework.
So, we have two drivers dedicated to the same type of hardware, but 
intented to be used with different topologies in IIO.
I used "backend" suffix as a differentiator here.
I did not find a better alternative to manage this diversity.
If, you have another suggestion please let me know.

>> +      - ads1201
> 
> Missing vendor prefix.
> 

Ack

BRs
Olivier

> Thanks,
> Conor.
> 
> 
>> +
>> +  '#io-backend-cells':
>> +    const: 0
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  vref-supply:
>> +    description: Phandle to the vref input analog reference voltage.
>> +
>> +required:
>> +  - compatible
>> +  - '#io-backend-cells'
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    ads1201: adc {
>> +      compatible = "sd-backend";
>> +      #io-backend-cells = <0>;
>> +    };
>> +
>> +...
>> -- 
>> 2.25.1
>>