[PATCH 0/3] iio: adc: stm32: add mdf support for stm32mp2

[PATCH 0/3] iio: adc: stm32: add mdf support for stm32mp2

[Olivier Moysan]

This series adds support for the STM32 Multi-function Digital Filter (MDF)
found on STM32MP2 SoCs. MDF filters bitstreams from external sigma-delta
modulators and PDM microphones into samples for IIO and ASoC consumers.

The first patch documents the MDF core, serial interfaces, filters and
their connections in the devicetree binding.

The second patch adds the core, serial interface and filter drivers.
It supports IIO voltage channels for external sigma-delta modulators,
with direct reads or DMA buffering, and PDM microphone capture through
a cyclic DMA buffer. It also provides CIC filter configuration,
synchronization and filter interleaving.

The lastest patches add an ASoC DAI for PDM microphone capture.

Olivier Moysan (3):
  dt-bindings: iio: adc: add bindings for stm32 mdf filter
  iio: adc: add stm32 mdf support
  ASoC: stm32: add mdf dai support

 .../bindings/iio/adc/st,stm32-mdf-adc.yaml    |  383 +++
 drivers/iio/adc/Kconfig                       |   27 +
 drivers/iio/adc/Makefile                      |    3 +
 drivers/iio/adc/stm32-mdf-adc.c               | 2078 +++++++++++++++++
 drivers/iio/adc/stm32-mdf-core.c              |  857 +++++++
 drivers/iio/adc/stm32-mdf-serial.c            |  309 +++
 drivers/iio/adc/stm32-mdf.h                   |  312 +++
 include/linux/iio/adc/stm32-mdf-adc.h         |   19 +
 sound/soc/stm/Kconfig                         |   15 +
 sound/soc/stm/Makefile                        |    3 +
 sound/soc/stm/stm32_amdf.c                    |  376 +++
 11 files changed, 4382 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
 create mode 100644 drivers/iio/adc/stm32-mdf-adc.c
 create mode 100644 drivers/iio/adc/stm32-mdf-core.c
 create mode 100644 drivers/iio/adc/stm32-mdf-serial.c
 create mode 100644 drivers/iio/adc/stm32-mdf.h
 create mode 100644 include/linux/iio/adc/stm32-mdf-adc.h
 create mode 100644 sound/soc/stm/stm32_amdf.c


base-commit: 9ee8306121495d2a25aa5d1bfd519f2748786b83
-- 
2.43.0

[PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Olivier Moysan]

Add bindings that describes STM32 MDF settings to support
digital filtering for Pulse Density Modulation (PDM) microphones
and analog sigma delta modulators.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
 1 file changed, 383 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
new file mode 100644
index 000000000000..f2fbc3e150e8
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
@@ -0,0 +1,383 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
+
+maintainers:
+  - Olivier Moysan <olivier.moysan@foss.st.com>
+
+description: |
+  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
+  interface external sigma delta modulators to STM32 micro controllers.
+
+properties:
+  compatible:
+    enum:
+      - st,stm32mp25-mdf
+      - st,stm32mp23-mdf
+
+  reg:
+    minItems: 1
+    maxItems: 2
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    description: Internal clock used for MDF digital processing.
+    items:
+      - const: ker_ck
+
+  "#clock-cells":
+    enum: [0, 1]
+
+  clock-output-names:
+    description: |
+      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
+      but can be gated independently to save power.
+    minItems: 1
+    maxItems: 2
+    oneOf:
+      - items:
+          - const: cck0
+      - items:
+          - const: cck1
+      - items:
+          - const: cck0
+          - const: cck1
+
+  clock-frequency:
+    description: |
+      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
+      The frequency must be a multiple of the "ker_ck" clock frequency.
+    maximum: 25000000
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+  ranges: true
+
+  clock-ranges: true
+
+  resets:
+    maxItems: 1
+
+  reset-names:
+    items:
+      - const: mdf
+
+  access-controllers:
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    description: |
+      Phandle to the rifsc device to check access right.
+
+  power-domains:
+    maxItems: 1
+
+  st,interleave:
+    description: |
+      List of phandles of interleaved filters. The indexes of interleaved filters must be
+      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
+      are muxed in a single channel and retrieved through the device associated to the filter 0.
+      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+
+required:
+  - compatible
+  - reg
+  - ranges
+  - clocks
+  - clock-names
+  - clock-ranges
+  - "#address-cells"
+  - "#size-cells"
+
+additionalProperties: false
+
+patternProperties:
+  "^sitf@[0-9]+$":
+    type: object
+    description: Serial interface child node
+
+    properties:
+      compatible:
+        enum:
+          - st,stm32mp25-sitf-mdf
+
+      reg:
+        description: Specify the SITF serial interface instance
+        maxItems: 1
+
+      clocks:
+        description: |
+          Serial interface clock (optional depending on interface mode)
+        maxItems: 1
+
+      st,sitf-mode:
+        description: |
+          Select serial interface protocol
+          - spi: SPI mode
+          - lf_spi: low frequency SPI mode for low power applications
+        $ref: /schemas/types.yaml#/definitions/string
+        enum:
+          - spi
+          - lf_spi
+
+    required:
+      - reg
+      - st,sitf-mode
+
+    additionalProperties: false
+
+  "^filter@[0-9]+$":
+    type: object
+    description: Digital filter path child node
+
+    properties:
+      compatible:
+        enum:
+          - st,stm32mp25-mdf-dmic
+          - st,stm32mp25-mdf-adc
+
+      reg:
+        description: Specify the MDF filter instance
+        maxItems: 1
+
+      interrupts:
+        maxItems: 1
+
+      clocks:
+        minItems: 1
+        description: Internal clock used for MDF digital processing and control blocks.
+
+      clock-names:
+        items:
+          - const: ker_ck
+
+      dmas:
+        maxItems: 1
+
+      dma-names:
+        items:
+          - const: rx
+
+      "#io-channel-cells":
+        const: 1
+
+      '#address-cells':
+        const: 1
+
+      '#size-cells':
+        const: 0
+
+      st,cic-mode:
+        description: |
+          Cascaded-integrator-comb (CIC) filter configuration
+          - 0: MCIC & ACIC filters in FastSinc mode
+          - [1-3]: MCIC & ACIC filters in Sinc mode order 1 to 3
+          - [4-5]: Single CIC filter in Sinc mode order 4 to 5
+          For audio purpose it is recommended to use CIC Sinc4 or Sinc5
+          This property is mandatory for filter 0 or filters not used in interleave mode.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 5
+
+      st,delay:
+        description: Filter delay in samples
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 127
+
+      st,rs-filter-bypass:
+        description: Bypass RSFLT reshaping filter.
+        $ref: /schemas/types.yaml#/definitions/flag
+
+      st,hpf-filter-cutoff-bp:
+        description: |
+          High Pass Filter (HPF) cut-off frequency expressed as a fraction of the PCM sampling rate.
+          Cut-off frequency = st,hpf-filter-cutoff-bp x Fpcm / 10000.
+          If this property is not defined the HPF is disabled.
+        enum: [625, 1250, 2500, 9500]
+
+      st,sync:
+        description:
+          Synchronize to another filter.
+          Must contain the phandle of the filter providing the synchronization.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/phandle-array
+          - maxItems: 1
+
+      st,sitf:
+        $ref: /schemas/types.yaml#/definitions/phandle-array
+        items:
+          - items:
+              - description: Phandle of the serial interface connected to the digital filter
+              - description: |
+                  The phandle's argument selects the bitstream on the falling or rising edge
+                  of the serial interface clock:
+                  - 0: rising edge
+                  - 1: falling edge
+                enum: [0, 1]
+                default: 0
+        description:
+          Should be phandle/bitstream pair.
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+      - dmas
+      - dma-names
+      - "#io-channel-cells"
+      - "#address-cells"
+      - "#size-cells"
+      - st,sitf
+
+    unevaluatedProperties: false
+
+    patternProperties:
+      "^channel@([0-7])$":
+        type: object
+        $ref: adc.yaml
+        description: Represents the external channel which is connected to the MDF.
+
+        properties:
+          reg:
+            maximum: 7
+
+          io-backends:
+            description:
+              Used to pipe external sigma delta modulator or internal ADC backend to MDF
+              channel.
+            maxItems: 1
+
+        required:
+          - reg
+
+        unevaluatedProperties: false
+
+    allOf:
+      - if:
+          properties:
+            compatible:
+              contains:
+                const: st,stm32mp25-mdf-adc
+
+        then:
+          patternProperties:
+            "^channel@[0-7]$":
+              required:
+                - io-backends
+
+      - if:
+          properties:
+            compatible:
+              contains:
+                const: st,stm32mp25-mdf-dmic
+
+        then:
+          patternProperties:
+            "^mdf-dai+$":
+              type: object
+              description: child node
+
+              properties:
+                compatible:
+                  enum:
+                    - st,stm32mp25-mdf-dai
+
+                "#sound-dai-cells":
+                  const: 0
+
+                io-channels:
+                  description:
+                    From common IIO binding. Used to pipe external sigma delta
+                    modulator or internal ADC output to MDF channel.
+
+                power-domains:
+                  maxItems: 1
+
+                port:
+                  $ref: /schemas/sound/audio-graph-port.yaml#
+                  unevaluatedProperties: false
+
+              required:
+                - compatible
+                - "#sound-dai-cells"
+                - io-channels
+
+              additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    mdf1: mdf@504d0000 {
+      compatible = "st,stm32mp25-mdf";
+      ranges = <0 0x504d0000 0x1000>;
+      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;
+      #address-cells = <1>;
+      #size-cells = <1>;
+      clocks = <&rcc CK_KER_MDF1>;
+      clock-names = "ker_ck";
+      clock-ranges;
+      #clock-cells = <1>;
+      clock-output-names = "cck0", "cck1";
+      clock-frequency = <2048000>;
+
+      sitf5: sitf@300 {
+        compatible = "st,stm32mp25-sitf-mdf";
+        reg = <0x300 0x4>;
+        st,sitf-mode = "spi";
+        clocks = <&mdf1 0>;
+      };
+
+      filter0: filter@84 {
+        compatible = "st,stm32mp25-mdf-dmic";
+        reg = <0x84 0x70>;
+        #io-channel-cells = <1>;
+        interrupts = <GIC_SPI 184 IRQ_TYPE_LEVEL_HIGH>;
+        dmas = <&hpdma 63 0x63 0x12 0>;
+        dma-names = "rx";
+        st,cic-mode = <5>;
+        st,sitf = <&sitf5 0>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        channel@0 {
+          reg = <0>;
+        };
+
+        asoc_pdm0: mdf-dai {
+          compatible = "st,stm32mp25-mdf-dai";
+          #sound-dai-cells = <0>;
+          io-channels = <&filter0 0>;
+        };
+      };
+
+      filter1: filter@104  {
+        compatible = "st,stm32mp25-mdf-adc";
+        reg = <0x104 0x70>;
+        #io-channel-cells = <1>;
+        interrupts = <GIC_SPI 185 IRQ_TYPE_LEVEL_HIGH>;
+        dmas = <&hpdma 64 0x63 0x12 0>;
+        dma-names = "rx";
+        st,cic-mode = <2>;
+        st,sitf = <&sitf5 1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        channel@1 {
+          reg = <1>;
+          settling-time-us = <1000>;
+          io-backends = <&sd_adc1>;
+        };
+      };
+    };
+
+...
-- 
2.43.0

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] dt-bindings: invalid decimal-only regex for sitf and filter unit addresses
- [Low] dt-bindings: faulty regex in mdf-dai and channel patternProperties
--

commit 0433e9502551ab7438d761bd69f15064435b1ccc
Author: Olivier Moysan <olivier.moysan@foss.st.com>

dt-bindings: iio: adc: add bindings for stm32 mdf filter

Add bindings that describes STM32 MDF settings to support
digital filtering for Pulse Density Modulation (PDM) microphones
and analog sigma delta modulators.

> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> new file mode 100644
> index 0000000000000..f2fbc3e150e8c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
[ ... ]
> +patternProperties:
> +  "^sitf@[0-9]+$":

[Severity: Low]
Is this regex overly restrictive? Device tree unit addresses commonly contain
hexadecimal characters, so an address like sitf@1a0 would fail to match this
pattern.

Since the top-level schema has additionalProperties: false, valid nodes might
be rejected. Would "^sitf@[0-9a-f]+$" be more appropriate?

> +    type: object
> +    description: Serial interface child node
[ ... ]
> +  "^filter@[0-9]+$":

[Severity: Low]
Similarly, does this restrict filter unit addresses strictly to decimal digits?

A node with a hexadecimal offset, such as filter@1e4, would not match this
pattern and would fail schema validation.

> +    type: object
> +    description: Digital filter path child node
[ ... ]
> +    patternProperties:
> +      "^channel@([0-7])$":

[Severity: Low]
Does this capture group differ from the allOf constraint key? The allOf section
later in the file uses "^channel@[0-7]$".

Mismatches in literal keys can sometimes interfere with schema aggregation
tools that rely on exact string matching to properly merge subschemas.

> +        type: object
> +        $ref: adc.yaml
[ ... ]
> +        then:
> +          patternProperties:
> +            "^mdf-dai+$":

[Severity: Low]
Could this regex pattern be a typo? The '+' quantifier applies to the character
'i' rather than matching multiple child nodes or strictly matching the string.

If it is meant to match exactly one string, would "^mdf-dai$" be intended?

> +              type: object
> +              description: child node

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261001145702.2628429-1-olivier.moysan@foss.st.com?part=1

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Rob Herring (Arm)]

On Thu, 01 Oct 2026 16:56:45 +0200, Olivier Moysan wrote:
> Add bindings that describes STM32 MDF settings to support
> digital filtering for Pulse Density Modulation (PDM) microphones
> and analog sigma delta modulators.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
>  1 file changed, 383 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
./Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml:363: example 0 [redundant-whitespace] extra whitespace before {

doc reference errors (make refcheckdocs):

See https://patchwork.kernel.org/project/devicetree/patch/20261001145702.2628429-2-olivier.moysan@foss.st.com

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 12687 bytes --]

On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
> Add bindings that describes STM32 MDF settings to support
> digital filtering for Pulse Density Modulation (PDM) microphones
> and analog sigma delta modulators.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
>  1 file changed, 383 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> new file mode 100644
> index 000000000000..f2fbc3e150e8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> @@ -0,0 +1,383 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
> +
> +maintainers:
> +  - Olivier Moysan <olivier.moysan@foss.st.com>
> +
> +description: |
> +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
> +  interface external sigma delta modulators to STM32 micro controllers.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - st,stm32mp25-mdf
> +      - st,stm32mp23-mdf
> +
> +  reg:
> +    minItems: 1
> +    maxItems: 2

This needs an items list here. The size of the regions seems like crap
to begin with...

> +
> +  clocks:
> +    maxItems: 1
> +
> +  clock-names:
> +    description: Internal clock used for MDF digital processing.
> +    items:
> +      - const: ker_ck

This is pointless when you only have one.

> +
> +  "#clock-cells":
> +    enum: [0, 1]

Why is this not fixed? Also why are parts of your own device consuming
the clocks?

> +
> +  clock-output-names:
> +    description: |
> +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
> +      but can be gated independently to save power.
> +    minItems: 1
> +    maxItems: 2
> +    oneOf:
> +      - items:
> +          - const: cck0
> +      - items:
> +          - const: cck1
> +      - items:
> +          - const: cck0
> +          - const: cck1
> +
> +  clock-frequency:
> +    description: |
> +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
> +      The frequency must be a multiple of the "ker_ck" clock frequency.
> +    maximum: 25000000

Should not be needed, the consumers request what they need.

> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 1
> +
> +  ranges: true
> +
> +  clock-ranges: true
> +
> +  resets:
> +    maxItems: 1
> +
> +  reset-names:
> +    items:
> +      - const: mdf
> +
> +  access-controllers:
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    description: |
> +      Phandle to the rifsc device to check access right.
> +
> +  power-domains:
> +    maxItems: 1
> +
> +  st,interleave:
> +    description: |
> +      List of phandles of interleaved filters. The indexes of interleaved filters must be
> +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
> +      are muxed in a single channel and retrieved through the device associated to the filter 0.
> +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
> +    $ref: /schemas/types.yaml#/definitions/phandle-array

No idea what these even are, but this is probably not the right way to
represent the relationship between devices. They're apparently ADCs, but
this is also an ADC so I'm not sure what's going on here at all.

> +
> +required:
> +  - compatible
> +  - reg
> +  - ranges
> +  - clocks
> +  - clock-names
> +  - clock-ranges
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +additionalProperties: false
> +
> +patternProperties:
> +  "^sitf@[0-9]+$":
> +    type: object
> +    description: Serial interface child node

Why is this a child node at all?
 
Probably not worth reviewing more without a link to the docs for this
device so I can figure out what on earth is going on!

Thanks,
Conor.

> +
> +    properties:
> +      compatible:
> +        enum:
> +          - st,stm32mp25-sitf-mdf
> +
> +      reg:
> +        description: Specify the SITF serial interface instance
> +        maxItems: 1
> +
> +      clocks:
> +        description: |
> +          Serial interface clock (optional depending on interface mode)
> +        maxItems: 1
> +
> +      st,sitf-mode:
> +        description: |
> +          Select serial interface protocol
> +          - spi: SPI mode
> +          - lf_spi: low frequency SPI mode for low power applications
> +        $ref: /schemas/types.yaml#/definitions/string
> +        enum:
> +          - spi
> +          - lf_spi
> +
> +    required:
> +      - reg
> +      - st,sitf-mode
> +
> +    additionalProperties: false
> +
> +  "^filter@[0-9]+$":
> +    type: object
> +    description: Digital filter path child node
> +
> +    properties:
> +      compatible:
> +        enum:
> +          - st,stm32mp25-mdf-dmic
> +          - st,stm32mp25-mdf-adc
> +
> +      reg:
> +        description: Specify the MDF filter instance
> +        maxItems: 1
> +
> +      interrupts:
> +        maxItems: 1
> +
> +      clocks:
> +        minItems: 1
> +        description: Internal clock used for MDF digital processing and control blocks.
> +
> +      clock-names:
> +        items:
> +          - const: ker_ck
> +
> +      dmas:
> +        maxItems: 1
> +
> +      dma-names:
> +        items:
> +          - const: rx
> +
> +      "#io-channel-cells":
> +        const: 1
> +
> +      '#address-cells':
> +        const: 1
> +
> +      '#size-cells':
> +        const: 0
> +
> +      st,cic-mode:
> +        description: |
> +          Cascaded-integrator-comb (CIC) filter configuration
> +          - 0: MCIC & ACIC filters in FastSinc mode
> +          - [1-3]: MCIC & ACIC filters in Sinc mode order 1 to 3
> +          - [4-5]: Single CIC filter in Sinc mode order 4 to 5
> +          For audio purpose it is recommended to use CIC Sinc4 or Sinc5
> +          This property is mandatory for filter 0 or filters not used in interleave mode.
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        minimum: 0
> +        maximum: 5
> +
> +      st,delay:
> +        description: Filter delay in samples
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        maximum: 127
> +
> +      st,rs-filter-bypass:
> +        description: Bypass RSFLT reshaping filter.
> +        $ref: /schemas/types.yaml#/definitions/flag
> +
> +      st,hpf-filter-cutoff-bp:
> +        description: |
> +          High Pass Filter (HPF) cut-off frequency expressed as a fraction of the PCM sampling rate.
> +          Cut-off frequency = st,hpf-filter-cutoff-bp x Fpcm / 10000.
> +          If this property is not defined the HPF is disabled.
> +        enum: [625, 1250, 2500, 9500]
> +
> +      st,sync:
> +        description:
> +          Synchronize to another filter.
> +          Must contain the phandle of the filter providing the synchronization.
> +        allOf:
> +          - $ref: /schemas/types.yaml#/definitions/phandle-array
> +          - maxItems: 1
> +
> +      st,sitf:
> +        $ref: /schemas/types.yaml#/definitions/phandle-array
> +        items:
> +          - items:
> +              - description: Phandle of the serial interface connected to the digital filter
> +              - description: |
> +                  The phandle's argument selects the bitstream on the falling or rising edge
> +                  of the serial interface clock:
> +                  - 0: rising edge
> +                  - 1: falling edge
> +                enum: [0, 1]
> +                default: 0
> +        description:
> +          Should be phandle/bitstream pair.
> +
> +    required:
> +      - compatible
> +      - reg
> +      - interrupts
> +      - dmas
> +      - dma-names
> +      - "#io-channel-cells"
> +      - "#address-cells"
> +      - "#size-cells"
> +      - st,sitf
> +
> +    unevaluatedProperties: false
> +
> +    patternProperties:
> +      "^channel@([0-7])$":
> +        type: object
> +        $ref: adc.yaml
> +        description: Represents the external channel which is connected to the MDF.
> +
> +        properties:
> +          reg:
> +            maximum: 7
> +
> +          io-backends:
> +            description:
> +              Used to pipe external sigma delta modulator or internal ADC backend to MDF
> +              channel.
> +            maxItems: 1
> +
> +        required:
> +          - reg
> +
> +        unevaluatedProperties: false
> +
> +    allOf:
> +      - if:
> +          properties:
> +            compatible:
> +              contains:
> +                const: st,stm32mp25-mdf-adc
> +
> +        then:
> +          patternProperties:
> +            "^channel@[0-7]$":
> +              required:
> +                - io-backends
> +
> +      - if:
> +          properties:
> +            compatible:
> +              contains:
> +                const: st,stm32mp25-mdf-dmic
> +
> +        then:
> +          patternProperties:
> +            "^mdf-dai+$":
> +              type: object
> +              description: child node
> +
> +              properties:
> +                compatible:
> +                  enum:
> +                    - st,stm32mp25-mdf-dai
> +
> +                "#sound-dai-cells":
> +                  const: 0
> +
> +                io-channels:
> +                  description:
> +                    From common IIO binding. Used to pipe external sigma delta
> +                    modulator or internal ADC output to MDF channel.
> +
> +                power-domains:
> +                  maxItems: 1
> +
> +                port:
> +                  $ref: /schemas/sound/audio-graph-port.yaml#
> +                  unevaluatedProperties: false
> +
> +              required:
> +                - compatible
> +                - "#sound-dai-cells"
> +                - io-channels
> +
> +              additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    mdf1: mdf@504d0000 {
> +      compatible = "st,stm32mp25-mdf";
> +      ranges = <0 0x504d0000 0x1000>;
> +      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;
> +      #address-cells = <1>;
> +      #size-cells = <1>;
> +      clocks = <&rcc CK_KER_MDF1>;
> +      clock-names = "ker_ck";
> +      clock-ranges;
> +      #clock-cells = <1>;
> +      clock-output-names = "cck0", "cck1";
> +      clock-frequency = <2048000>;
> +
> +      sitf5: sitf@300 {
> +        compatible = "st,stm32mp25-sitf-mdf";
> +        reg = <0x300 0x4>;
> +        st,sitf-mode = "spi";
> +        clocks = <&mdf1 0>;
> +      };
> +
> +      filter0: filter@84 {
> +        compatible = "st,stm32mp25-mdf-dmic";
> +        reg = <0x84 0x70>;
> +        #io-channel-cells = <1>;
> +        interrupts = <GIC_SPI 184 IRQ_TYPE_LEVEL_HIGH>;
> +        dmas = <&hpdma 63 0x63 0x12 0>;
> +        dma-names = "rx";
> +        st,cic-mode = <5>;
> +        st,sitf = <&sitf5 0>;
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        channel@0 {
> +          reg = <0>;
> +        };
> +
> +        asoc_pdm0: mdf-dai {
> +          compatible = "st,stm32mp25-mdf-dai";
> +          #sound-dai-cells = <0>;
> +          io-channels = <&filter0 0>;
> +        };
> +      };
> +
> +      filter1: filter@104  {
> +        compatible = "st,stm32mp25-mdf-adc";
> +        reg = <0x104 0x70>;
> +        #io-channel-cells = <1>;
> +        interrupts = <GIC_SPI 185 IRQ_TYPE_LEVEL_HIGH>;
> +        dmas = <&hpdma 64 0x63 0x12 0>;
> +        dma-names = "rx";
> +        st,cic-mode = <2>;
> +        st,sitf = <&sitf5 1>;
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        channel@1 {
> +          reg = <1>;
> +          settling-time-us = <1000>;
> +          io-backends = <&sd_adc1>;
> +        };
> +      };
> +    };
> +
> +...
> -- 
> 2.43.0
> 

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Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Krzysztof Kozlowski]

On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
> Add bindings that describes STM32 MDF settings to support
> digital filtering for Pulse Density Modulation (PDM) microphones
> and analog sigma delta modulators.

You already received review, so a few things on top to spare you one
more cycle:

A nit, subject: drop second/last, redundant "bindings for". The
"dt-bindings" prefix is already stating that these are bindings.
See also:
https://elixir.bootlin.com/linux/v7.1-rc7/source/Documentation/devicetree/bindings/submitting-patches.rst#L23

> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
>  1 file changed, 383 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> new file mode 100644
> index 000000000000..f2fbc3e150e8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml

Filename follows compatible, so st,stm32mp23-mdf

> @@ -0,0 +1,383 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
> +
> +maintainers:
> +  - Olivier Moysan <olivier.moysan@foss.st.com>
> +
> +description: |
> +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
> +  interface external sigma delta modulators to STM32 micro controllers.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - st,stm32mp25-mdf
> +      - st,stm32mp23-mdf

Why reversed order?

> +  ranges: true
> +
> +  clock-ranges: true

Do you need it here?

> +
> +  resets:
> +    maxItems: 1
> +
> +  reset-names:
> +    items:
> +      - const: mdf

Drop

> +
> +  access-controllers:
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +    description: |
> +      Phandle to the rifsc device to check access right.

Look at other code how this is done. Don't come with own stuff.

> +
> +  power-domains:
> +    maxItems: 1
> +
> +  st,interleave:
> +    description: |
> +      List of phandles of interleaved filters. The indexes of interleaved filters must be
> +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
> +      are muxed in a single channel and retrieved through the device associated to the filter 0.
> +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +
> +required:
> +  - compatible
> +  - reg
> +  - ranges
> +  - clocks
> +  - clock-names
> +  - clock-ranges
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +additionalProperties: false
> +
> +patternProperties:

And this has odd order. Please look at example-schema.

> +  "^sitf@[0-9]+$":
> +    type: object
> +    description: Serial interface child node
> +
> +    properties:
> +      compatible:
> +        enum:
> +          - st,stm32mp25-sitf-mdf
> +
> +      reg:
> +        description: Specify the SITF serial interface instance
> +        maxItems: 1
> +
> +      clocks:
> +        description: |
> +          Serial interface clock (optional depending on interface mode)
> +        maxItems: 1
> +
> +      st,sitf-mode:
> +        description: |
> +          Select serial interface protocol
> +          - spi: SPI mode
> +          - lf_spi: low frequency SPI mode for low power applications
> +        $ref: /schemas/types.yaml#/definitions/string
> +        enum:
> +          - spi
> +          - lf_spi
> +
> +    required:
> +      - reg
> +      - st,sitf-mode
> +
> +    additionalProperties: false
> +
> +  "^filter@[0-9]+$":
> +    type: object
> +    description: Digital filter path child node
> +
> +    properties:
> +      compatible:
> +        enum:
> +          - st,stm32mp25-mdf-dmic
> +          - st,stm32mp25-mdf-adc
> +
> +      reg:
> +        description: Specify the MDF filter instance
> +        maxItems: 1
> +
> +      interrupts:
> +        maxItems: 1
> +
> +      clocks:
> +        minItems: 1

Heh? so here min? Is there any logic in your choices of code style?

> +        description: Internal clock used for MDF digital processing and control blocks.
> +
> +      clock-names:
> +        items:
> +          - const: ker_ck
> +
> +      dmas:
> +        maxItems: 1
> +
> +      dma-names:
> +        items:
> +          - const: rx
> +
> +      "#io-channel-cells":
> +        const: 1
> +
> +      '#address-cells':
> +        const: 1
> +
> +      '#size-cells':
> +        const: 0
> +
> +      st,cic-mode:
> +        description: |
> +          Cascaded-integrator-comb (CIC) filter configuration
> +          - 0: MCIC & ACIC filters in FastSinc mode
> +          - [1-3]: MCIC & ACIC filters in Sinc mode order 1 to 3
> +          - [4-5]: Single CIC filter in Sinc mode order 4 to 5
> +          For audio purpose it is recommended to use CIC Sinc4 or Sinc5
> +          This property is mandatory for filter 0 or filters not used in interleave mode.
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        minimum: 0
> +        maximum: 5
> +
> +      st,delay:
> +        description: Filter delay in samples
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        maximum: 127
> +
> +      st,rs-filter-bypass:
> +        description: Bypass RSFLT reshaping filter.
> +        $ref: /schemas/types.yaml#/definitions/flag
> +
> +      st,hpf-filter-cutoff-bp:
> +        description: |
> +          High Pass Filter (HPF) cut-off frequency expressed as a fraction of the PCM sampling rate.
> +          Cut-off frequency = st,hpf-filter-cutoff-bp x Fpcm / 10000.
> +          If this property is not defined the HPF is disabled.
> +        enum: [625, 1250, 2500, 9500]
> +
> +      st,sync:
> +        description:
> +          Synchronize to another filter.
> +          Must contain the phandle of the filter providing the synchronization.
> +        allOf:
> +          - $ref: /schemas/types.yaml#/definitions/phandle-array
> +          - maxItems: 1
> +
> +      st,sitf:
> +        $ref: /schemas/types.yaml#/definitions/phandle-array
> +        items:
> +          - items:
> +              - description: Phandle of the serial interface connected to the digital filter
> +              - description: |
> +                  The phandle's argument selects the bitstream on the falling or rising edge
> +                  of the serial interface clock:
> +                  - 0: rising edge
> +                  - 1: falling edge
> +                enum: [0, 1]
> +                default: 0
> +        description:
> +          Should be phandle/bitstream pair.
> +
> +    required:
> +      - compatible
> +      - reg
> +      - interrupts
> +      - dmas
> +      - dma-names
> +      - "#io-channel-cells"
> +      - "#address-cells"
> +      - "#size-cells"
> +      - st,sitf
> +
> +    unevaluatedProperties: false
> +
> +    patternProperties:
> +      "^channel@([0-7])$":
> +        type: object
> +        $ref: adc.yaml
> +        description: Represents the external channel which is connected to the MDF.
> +
> +        properties:
> +          reg:
> +            maximum: 7
> +
> +          io-backends:
> +            description:
> +              Used to pipe external sigma delta modulator or internal ADC backend to MDF
> +              channel.
> +            maxItems: 1
> +
> +        required:
> +          - reg
> +
> +        unevaluatedProperties: false
> +
> +    allOf:
> +      - if:
> +          properties:
> +            compatible:
> +              contains:
> +                const: st,stm32mp25-mdf-adc
> +
> +        then:
> +          patternProperties:
> +            "^channel@[0-7]$":
> +              required:
> +                - io-backends
> +
> +      - if:
> +          properties:
> +            compatible:
> +              contains:
> +                const: st,stm32mp25-mdf-dmic
> +
> +        then:
> +          patternProperties:
> +            "^mdf-dai+$":

This makes no sense. Why is this a pattern and why mdf-daiiiii is
correct name?

Not mentioning that your are not supposed to define properties in if
block (do you see any code like that?). Mixing addressable and
non-addressable children is another odd thing.

This entire schema is quite chaotic and overcomplicated.

> +              type: object
> +              description: child node
> +
> +              properties:
> +                compatible:
> +                  enum:
> +                    - st,stm32mp25-mdf-dai
> +
> +                "#sound-dai-cells":
> +                  const: 0
> +
> +                io-channels:
> +                  description:
> +                    From common IIO binding. Used to pipe external sigma delta
> +                    modulator or internal ADC output to MDF channel.
> +
> +                power-domains:
> +                  maxItems: 1
> +
> +                port:
> +                  $ref: /schemas/sound/audio-graph-port.yaml#
> +                  unevaluatedProperties: false
> +
> +              required:
> +                - compatible
> +                - "#sound-dai-cells"
> +                - io-channels
> +
> +              additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    mdf1: mdf@504d0000 {

Node names should be generic. See also an explanation and list of
examples (not exhaustive) in DT specification:
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
If you cannot find a name matching your device, please check in kernel
sources for similar cases or you can grow the spec (via pull request to
DT spec repo).

And drop unused labels.

> +      compatible = "st,stm32mp25-mdf";
> +      ranges = <0 0x504d0000 0x1000>;
> +      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;

Address ranges of 2 and 4 words?

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Krzysztof Kozlowski]

On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
> +  clock-output-names:
> +    description: |
> +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
> +      but can be gated independently to save power.
> +    minItems: 1
> +    maxItems: 2
> +    oneOf:
> +      - items:
> +          - const: cck0
> +      - items:
> +          - const: cck1
> +      - items:
> +          - const: cck0
> +          - const: cck1

Use simpler notation:
minItems: 1
items:
  - enum
  - const

> +
> +  clock-frequency:
> +    description: |

Drop | when not needed.

> +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
> +      The frequency must be a multiple of the "ker_ck" clock frequency.
> +    maximum: 25000000

So here is the clock-frequency. No, these are output clocks as written
above, so consumer sets it, not the provider. Or use existing assigned
properties. This is even mentioned on DTS101 slides, really...

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Olivier MOYSAN]

Hi Krzysztof,

Thank you for the review.

On 10/2/26 11:22, Krzysztof Kozlowski wrote:
> On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
>> Add bindings that describes STM32 MDF settings to support
>> digital filtering for Pulse Density Modulation (PDM) microphones
>> and analog sigma delta modulators.
> 
> You already received review, so a few things on top to spare you one
> more cycle:
> 
> A nit, subject: drop second/last, redundant "bindings for". The
> "dt-bindings" prefix is already stating that these are bindings.
> See also:
> https://elixir.bootlin.com/linux/v7.1-rc7/source/Documentation/devicetree/bindings/submitting-patches.rst#L23
> 

Done

>>
>> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
>> ---
>>   .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
>>   1 file changed, 383 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>> new file mode 100644
>> index 000000000000..f2fbc3e150e8
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> 
> Filename follows compatible, so st,stm32mp23-mdf
> 

stmp32mp25 is the main SoC, while stm32mp23 is a variant.
file renamed st,stm32mp25-mdf.yaml

>> @@ -0,0 +1,383 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
>> +
>> +maintainers:
>> +  - Olivier Moysan <olivier.moysan@foss.st.com>
>> +
>> +description: |
>> +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
>> +  interface external sigma delta modulators to STM32 micro controllers.
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - st,stm32mp25-mdf
>> +      - st,stm32mp23-mdf
> 
> Why reversed order?
> 

Ok. Reordered alphabetically

>> +  ranges: true
>> +
>> +  clock-ranges: true
> 
> Do you need it here?

clock-ranges property is used to allow the filter child nodes to inherit 
the MDF kernel clock from the parent node.

> 
>> +
>> +  resets:
>> +    maxItems: 1
>> +
>> +  reset-names:
>> +    items:
>> +      - const: mdf
> 
> Drop
> 

reset-names removed.

>> +
>> +  access-controllers:
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +    description: |
>> +      Phandle to the rifsc device to check access right.
> 
> Look at other code how this is done. Don't come with own stuff.
> 

Replaced by:
   access-controllers:
     maxItems: 1

>> +
>> +  power-domains:
>> +    maxItems: 1
>> +
>> +  st,interleave:
>> +    description: |
>> +      List of phandles of interleaved filters. The indexes of interleaved filters must be
>> +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
>> +      are muxed in a single channel and retrieved through the device associated to the filter 0.
>> +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - ranges
>> +  - clocks
>> +  - clock-names
>> +  - clock-ranges
>> +  - "#address-cells"
>> +  - "#size-cells"
>> +
>> +additionalProperties: false
>> +
>> +patternProperties:
> 
> And this has odd order. Please look at example-schema.
> 

ok. Reordered.

>> +  "^sitf@[0-9]+$":
>> +    type: object
>> +    description: Serial interface child node
>> +
>> +    properties:
>> +      compatible:
>> +        enum:
>> +          - st,stm32mp25-sitf-mdf
>> +
>> +      reg:
>> +        description: Specify the SITF serial interface instance
>> +        maxItems: 1
>> +
>> +      clocks:
>> +        description: |
>> +          Serial interface clock (optional depending on interface mode)
>> +        maxItems: 1
>> +
>> +      st,sitf-mode:
>> +        description: |
>> +          Select serial interface protocol
>> +          - spi: SPI mode
>> +          - lf_spi: low frequency SPI mode for low power applications
>> +        $ref: /schemas/types.yaml#/definitions/string
>> +        enum:
>> +          - spi
>> +          - lf_spi
>> +
>> +    required:
>> +      - reg
>> +      - st,sitf-mode
>> +
>> +    additionalProperties: false
>> +
>> +  "^filter@[0-9]+$":
>> +    type: object
>> +    description: Digital filter path child node
>> +
>> +    properties:
>> +      compatible:
>> +        enum:
>> +          - st,stm32mp25-mdf-dmic
>> +          - st,stm32mp25-mdf-adc
>> +
>> +      reg:
>> +        description: Specify the MDF filter instance
>> +        maxItems: 1
>> +
>> +      interrupts:
>> +        maxItems: 1
>> +
>> +      clocks:
>> +        minItems: 1
> 
> Heh? so here min? Is there any logic in your choices of code style?
> 

As the filter node always use the kernel clock from parent node we can 
remove "clocks" item. "clocks" is not relevant here as the filter is not 
supposed to use another reference.
clocks & clock-names removed

>> +        description: Internal clock used for MDF digital processing and control blocks.
>> +
>> +      clock-names:
>> +        items:
>> +          - const: ker_ck
>> +
>> +      dmas:
>> +        maxItems: 1
>> +
>> +      dma-names:
>> +        items:
>> +          - const: rx
>> +
>> +      "#io-channel-cells":
>> +        const: 1
>> +
>> +      '#address-cells':
>> +        const: 1
>> +
>> +      '#size-cells':
>> +        const: 0
>> +
>> +      st,cic-mode:
>> +        description: |
>> +          Cascaded-integrator-comb (CIC) filter configuration
>> +          - 0: MCIC & ACIC filters in FastSinc mode
>> +          - [1-3]: MCIC & ACIC filters in Sinc mode order 1 to 3
>> +          - [4-5]: Single CIC filter in Sinc mode order 4 to 5
>> +          For audio purpose it is recommended to use CIC Sinc4 or Sinc5
>> +          This property is mandatory for filter 0 or filters not used in interleave mode.
>> +        $ref: /schemas/types.yaml#/definitions/uint32
>> +        minimum: 0
>> +        maximum: 5
>> +
>> +      st,delay:
>> +        description: Filter delay in samples
>> +        $ref: /schemas/types.yaml#/definitions/uint32
>> +        maximum: 127
>> +
>> +      st,rs-filter-bypass:
>> +        description: Bypass RSFLT reshaping filter.
>> +        $ref: /schemas/types.yaml#/definitions/flag
>> +
>> +      st,hpf-filter-cutoff-bp:
>> +        description: |
>> +          High Pass Filter (HPF) cut-off frequency expressed as a fraction of the PCM sampling rate.
>> +          Cut-off frequency = st,hpf-filter-cutoff-bp x Fpcm / 10000.
>> +          If this property is not defined the HPF is disabled.
>> +        enum: [625, 1250, 2500, 9500]
>> +
>> +      st,sync:
>> +        description:
>> +          Synchronize to another filter.
>> +          Must contain the phandle of the filter providing the synchronization.
>> +        allOf:
>> +          - $ref: /schemas/types.yaml#/definitions/phandle-array
>> +          - maxItems: 1
>> +
>> +      st,sitf:
>> +        $ref: /schemas/types.yaml#/definitions/phandle-array
>> +        items:
>> +          - items:
>> +              - description: Phandle of the serial interface connected to the digital filter
>> +              - description: |
>> +                  The phandle's argument selects the bitstream on the falling or rising edge
>> +                  of the serial interface clock:
>> +                  - 0: rising edge
>> +                  - 1: falling edge
>> +                enum: [0, 1]
>> +                default: 0
>> +        description:
>> +          Should be phandle/bitstream pair.
>> +
>> +    required:
>> +      - compatible
>> +      - reg
>> +      - interrupts
>> +      - dmas
>> +      - dma-names
>> +      - "#io-channel-cells"
>> +      - "#address-cells"
>> +      - "#size-cells"
>> +      - st,sitf
>> +
>> +    unevaluatedProperties: false
>> +
>> +    patternProperties:
>> +      "^channel@([0-7])$":
>> +        type: object
>> +        $ref: adc.yaml
>> +        description: Represents the external channel which is connected to the MDF.
>> +
>> +        properties:
>> +          reg:
>> +            maximum: 7
>> +
>> +          io-backends:
>> +            description:
>> +              Used to pipe external sigma delta modulator or internal ADC backend to MDF
>> +              channel.
>> +            maxItems: 1
>> +
>> +        required:
>> +          - reg
>> +
>> +        unevaluatedProperties: false
>> +
>> +    allOf:
>> +      - if:
>> +          properties:
>> +            compatible:
>> +              contains:
>> +                const: st,stm32mp25-mdf-adc
>> +
>> +        then:
>> +          patternProperties:
>> +            "^channel@[0-7]$":
>> +              required:
>> +                - io-backends
>> +
>> +      - if:
>> +          properties:
>> +            compatible:
>> +              contains:
>> +                const: st,stm32mp25-mdf-dmic
>> +
>> +        then:
>> +          patternProperties:
>> +            "^mdf-dai+$":
> 
> This makes no sense. Why is this a pattern and why mdf-daiiiii is
> correct name?
> 

"^mdf-dai$" is intended here

> Not mentioning that your are not supposed to define properties in if
> block (do you see any code like that?). Mixing addressable and
> non-addressable children is another odd thing.
> 

This binding is inspired by the one already adopted for the DFSDM
https://www.kernel.org/doc/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml

I assume can move the mdf-dai node definition outside the conditional 
branch easily.
However, it seems to me more complicated to avoid mixing addressable and 
non-addressable nodes here. Can we keep this binding aligned with the 
DFSDM model? Or would you have another suggestion?

> This entire schema is quite chaotic and overcomplicated.
> 
>> +              type: object
>> +              description: child node
>> +
>> +              properties:
>> +                compatible:
>> +                  enum:
>> +                    - st,stm32mp25-mdf-dai
>> +
>> +                "#sound-dai-cells":
>> +                  const: 0
>> +
>> +                io-channels:
>> +                  description:
>> +                    From common IIO binding. Used to pipe external sigma delta
>> +                    modulator or internal ADC output to MDF channel.
>> +
>> +                power-domains:
>> +                  maxItems: 1
>> +
>> +                port:
>> +                  $ref: /schemas/sound/audio-graph-port.yaml#
>> +                  unevaluatedProperties: false
>> +
>> +              required:
>> +                - compatible
>> +                - "#sound-dai-cells"
>> +                - io-channels
>> +
>> +              additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +    mdf1: mdf@504d0000 {
> 
> Node names should be generic. See also an explanation and list of
> examples (not exhaustive) in DT specification:
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
> If you cannot find a name matching your device, please check in kernel
> sources for similar cases or you can grow the spec (via pull request to
> DT spec repo).
> 
> And drop unused labels.
> 

The MDF is a digital filter for sigma-delta bitstreams, rather than the 
analog-to-digital converter itself. So "adc" would not be adapted. I did 
not find "filter", that probably would be the more relevant generic name.
The closest similar case is the DFSDM peripheral, which already uses a 
specific naming:
     dfsdm: dfsdm@4400d000 { ...
https://www.kernel.org/doc/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml

What is your recommendation: keep the naming "mdf" or make a pull 
request to add "filter" or another more appropriate name ?

>> +      compatible = "st,stm32mp25-mdf";
>> +      ranges = <0 0x504d0000 0x1000>;
>> +      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;
> 
> Address ranges of 2 and 4 words?
> 

These two sections correspond to MDF common registers managed by the core
- Control registers: 2 x 32 bits registers
- Identification registers: 4 x 32 bits registers
The other registers are managed by filter and serial interface driver

> Best regards,
> Krzysztof
> 

Best regards
Olivier

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Krzysztof Kozlowski]

On 06/10/2026 17:48, Olivier MOYSAN wrote:
>>>
>>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>> new file mode 100644
>>> index 000000000000..f2fbc3e150e8
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>
>> Filename follows compatible, so st,stm32mp23-mdf
>>
> 
> stmp32mp25 is the main SoC, while stm32mp23 is a variant.
> file renamed st,stm32mp25-mdf.yaml

Sure, that's fine.

> 
>>> @@ -0,0 +1,383 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
>>> +
>>> +maintainers:
>>> +  - Olivier Moysan <olivier.moysan@foss.st.com>
>>> +
>>> +description: |
>>> +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
>>> +  interface external sigma delta modulators to STM32 micro controllers.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - st,stm32mp25-mdf
>>> +      - st,stm32mp23-mdf
>>
>> Why reversed order?
>>
> 
> Ok. Reordered alphabetically
> 
>>> +  ranges: true
>>> +
>>> +  clock-ranges: true
>>
>> Do you need it here?
> 
> clock-ranges property is used to allow the filter child nodes to inherit 
> the MDF kernel clock from the parent node.

You answered why you need it in DTS. I question why do you need it in
the binding? Do you see a warning?

> 
>>
>>> +
>>> +  resets:
>>> +    maxItems: 1
>>> +
>>> +  reset-names:
>>> +    items:
>>> +      - const: mdf


>>> +        then:
>>> +          patternProperties:
>>> +            "^channel@[0-7]$":
>>> +              required:
>>> +                - io-backends
>>> +
>>> +      - if:
>>> +          properties:
>>> +            compatible:
>>> +              contains:
>>> +                const: st,stm32mp25-mdf-dmic
>>> +
>>> +        then:
>>> +          patternProperties:
>>> +            "^mdf-dai+$":
>>
>> This makes no sense. Why is this a pattern and why mdf-daiiiii is
>> correct name?
>>
> 
> "^mdf-dai$" is intended here
> 
>> Not mentioning that your are not supposed to define properties in if
>> block (do you see any code like that?). Mixing addressable and
>> non-addressable children is another odd thing.
>>
> 
> This binding is inspired by the one already adopted for the DFSDM
> https://www.kernel.org/doc/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml
> 
> I assume can move the mdf-dai node definition outside the conditional 
> branch easily.
> However, it seems to me more complicated to avoid mixing addressable and 
> non-addressable nodes here. Can we keep this binding aligned with the 
> DFSDM model? Or would you have another suggestion?

Why was this model chosen in that dfsdm? The child has no resources, so
it should never been made a separate node.


> 
>> This entire schema is quite chaotic and overcomplicated.
>>
>>> +              type: object
>>> +              description: child node
>>> +
>>> +              properties:
>>> +                compatible:
>>> +                  enum:
>>> +                    - st,stm32mp25-mdf-dai
>>> +
>>> +                "#sound-dai-cells":
>>> +                  const: 0
>>> +
>>> +                io-channels:
>>> +                  description:
>>> +                    From common IIO binding. Used to pipe external sigma delta
>>> +                    modulator or internal ADC output to MDF channel.
>>> +
>>> +                power-domains:
>>> +                  maxItems: 1
>>> +
>>> +                port:
>>> +                  $ref: /schemas/sound/audio-graph-port.yaml#
>>> +                  unevaluatedProperties: false
>>> +
>>> +              required:
>>> +                - compatible
>>> +                - "#sound-dai-cells"
>>> +                - io-channels
>>> +
>>> +              additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
>>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>>> +    mdf1: mdf@504d0000 {
>>
>> Node names should be generic. See also an explanation and list of
>> examples (not exhaustive) in DT specification:
>> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
>> If you cannot find a name matching your device, please check in kernel
>> sources for similar cases or you can grow the spec (via pull request to
>> DT spec repo).
>>
>> And drop unused labels.
>>
> 
> The MDF is a digital filter for sigma-delta bitstreams, rather than the 
> analog-to-digital converter itself. So "adc" would not be adapted. I did 
> not find "filter", that probably would be the more relevant generic name.
> The closest similar case is the DFSDM peripheral, which already uses a 
> specific naming:
>      dfsdm: dfsdm@4400d000 { ...
> https://www.kernel.org/doc/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml
> 
> What is your recommendation: keep the naming "mdf" or make a pull 
> request to add "filter" or another more appropriate name ?
> 
>>> +      compatible = "st,stm32mp25-mdf";
>>> +      ranges = <0 0x504d0000 0x1000>;
>>> +      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;
>>
>> Address ranges of 2 and 4 words?
>>
> 
> These two sections correspond to MDF common registers managed by the core
> - Control registers: 2 x 32 bits registers
> - Identification registers: 4 x 32 bits registers
> The other registers are managed by filter and serial interface driver
> 


Unfortunately this leaves impression of incomplete DT or too granular
split of devices to match your driver model.

Best regards,
Krzysztof

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Olivier MOYSAN]

Hi Krzysztof,

On 10/2/26 11:34, Krzysztof Kozlowski wrote:
> On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
>> +  clock-output-names:
>> +    description: |
>> +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
>> +      but can be gated independently to save power.
>> +    minItems: 1
>> +    maxItems: 2
>> +    oneOf:
>> +      - items:
>> +          - const: cck0
>> +      - items:
>> +          - const: cck1
>> +      - items:
>> +          - const: cck0
>> +          - const: cck1
> 
> Use simpler notation:
> minItems: 1
> items:
>    - enum
>    - const
> 
>> +
>> +  clock-frequency:
>> +    description: |
> 
> Drop | when not needed.
> 
>> +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
>> +      The frequency must be a multiple of the "ker_ck" clock frequency.
>> +    maximum: 25000000
> 
> So here is the clock-frequency. No, these are output clocks as written
> above, so consumer sets it, not the provider. Or use existing assigned
> properties. This is even mentioned on DTS101 slides, really...
> 

We expect the clock frequency to be defined statically for a given board 
So, using assigned-clocks properties looks the right choice.
What bothers me about this solution, is that the frequency will be 
defined in each consumer, whereas a single rate can be defined for the 
provider. This may looks a bit strange, but I will implement it this way 
if there is no other mean to set the provider frequency.


> Best regards,
> Krzysztof
> 

Best regards
Olivier

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Olivier MOYSAN]

Hi Conor,

Thanks for the review

On 10/1/26 20:32, Conor Dooley wrote:
> On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
>> Add bindings that describes STM32 MDF settings to support
>> digital filtering for Pulse Density Modulation (PDM) microphones
>> and analog sigma delta modulators.
>>
>> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
>> ---
>>   .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
>>   1 file changed, 383 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>> new file mode 100644
>> index 000000000000..f2fbc3e150e8
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>> @@ -0,0 +1,383 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
>> +
>> +maintainers:
>> +  - Olivier Moysan <olivier.moysan@foss.st.com>
>> +
>> +description: |
>> +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
>> +  interface external sigma delta modulators to STM32 micro controllers.
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - st,stm32mp25-mdf
>> +      - st,stm32mp23-mdf
>> +
>> +  reg:
>> +    minItems: 1
>> +    maxItems: 2
> 
> This needs an items list here. The size of the regions seems like crap
> to begin with...
> 
>> +
>> +  clocks:
>> +    maxItems: 1
>> +
>> +  clock-names:
>> +    description: Internal clock used for MDF digital processing.
>> +    items:
>> +      - const: ker_ck
> 
> This is pointless when you only have one.
> 

I agree that it could be dropped. However, it is useful for using 
devm_regmap_init_mmio_clk.

>> +
>> +  "#clock-cells":
>> +    enum: [0, 1]
> 
> Why is this not fixed? Also why are parts of your own device consuming
> the clocks?
> 
>> +
>> +  clock-output-names:
>> +    description: |
>> +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
>> +      but can be gated independently to save power.
>> +    minItems: 1
>> +    maxItems: 2
>> +    oneOf:
>> +      - items:
>> +          - const: cck0
>> +      - items:
>> +          - const: cck1
>> +      - items:
>> +          - const: cck0
>> +          - const: cck1
>> +
>> +  clock-frequency:
>> +    description: |
>> +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
>> +      The frequency must be a multiple of the "ker_ck" clock frequency.
>> +    maximum: 25000000
> 
> Should not be needed, the consumers request what they need.
> 

The CCKx clock frequency depends on the maximum rate supported by the 
sigma delta converters (for instance a digital mic) and the expected 
decimation ratio on the bitstream. Typically this determines the 
frequency on the SPI bus.
This rate is defined statically and shared by the CCKx clocks. So IMHO, 
as this rate is unique, it can look strange to let the consumer define 
it. Moreover, it seems to me that clock-frequency is already used to 
configure the frequency of a provider in some other bindings.
For instance: Documentation/devicetree/bindings/clock/silabs,si570.yaml
So, it's not clear for me, what is the restriction on clock-frequency 
property.
>> +
>> +  ranges: true
>> +
>> +  clock-ranges: true
>> +
>> +  resets:
>> +    maxItems: 1
>> +
>> +  reset-names:
>> +    items:
>> +      - const: mdf
>> +
>> +  access-controllers:
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +    description: |
>> +      Phandle to the rifsc device to check access right.
>> +
>> +  power-domains:
>> +    maxItems: 1
>> +
>> +  st,interleave:
>> +    description: |
>> +      List of phandles of interleaved filters. The indexes of interleaved filters must be
>> +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
>> +      are muxed in a single channel and retrieved through the device associated to the filter 0.
>> +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> 
> No idea what these even are, but this is probably not the right way to
> represent the relationship between devices. They're apparently ADCs, but
> this is also an ADC so I'm not sure what's going on here at all.
> 
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - ranges
>> +  - clocks
>> +  - clock-names
>> +  - clock-ranges
>> +  - "#address-cells"
>> +  - "#size-cells"
>> +
>> +additionalProperties: false
>> +
>> +patternProperties:
>> +  "^sitf@[0-9]+$":
>> +    type: object
>> +    description: Serial interface child node
> 
> Why is this a child node at all?
>   
> Probably not worth reviewing more without a link to the docs for this
> device so I can figure out what on earth is going on!
> 

The MDF is a digital filter for sigma-delta bitstreams, rather than the 
analog-to-digital converter itself.

Here is the link to STM32MP25 reference manuel
https://www.st.com/resource/en/reference_manual/rm0457-stm32mp2325xx-advanced-armbased-3264bit-mpus-stmicroelectronics.pdf
Chapter 45: Multi-function digital filter (MDF)

On STMP32MP25 SoC, the MDF provides 8 serial interfaces (SITF) and 8 
digital filters (DFLT) which can be connected through a multiplexer.

Below is a schematic view of typical applications targeted by this 
peripheral


Audio use case:

		mdf
             +-------------------------------------+
+------+    | +------+    +------+    +------+    |
| dmic | -> | | sitf | -> | mux  | -> | dflt | -- | -> audio device
+------+    | +------+    +------+    +------+    |
             +-------------------------------------+

For instance, in an audio use case the serial interface can be 
configured to provide the clock to the digital microphone (cck0, cck1 or 
both) at a common predefined rate, and to retrieve the PDM samples.
The serial interface provides this samples to a digital filter, which 
delivers PCM samples on its output.


Analog use case:

		mdf
               +-------------------------------------+
+--------+    | +------+    +------+    +------+    |
| sd adc | -> | | sitf | -> | mux  | -> | dflt | -- | -> iio device
+--------+    | +------+    +------+    +------+    |
               +-------------------------------------+


Best regards
Olivier

> Thanks,
> Conor.
> 
>> +
>> +    properties:
>> +      compatible:
>> +        enum:
>> +          - st,stm32mp25-sitf-mdf
>> +
>> +      reg:
>> +        description: Specify the SITF serial interface instance
>> +        maxItems: 1
>> +
>> +      clocks:
>> +        description: |
>> +          Serial interface clock (optional depending on interface mode)
>> +        maxItems: 1
>> +
>> +      st,sitf-mode:
>> +        description: |
>> +          Select serial interface protocol
>> +          - spi: SPI mode
>> +          - lf_spi: low frequency SPI mode for low power applications
>> +        $ref: /schemas/types.yaml#/definitions/string
>> +        enum:
>> +          - spi
>> +          - lf_spi
>> +
>> +    required:
>> +      - reg
>> +      - st,sitf-mode
>> +
>> +    additionalProperties: false
>> +
>> +  "^filter@[0-9]+$":
>> +    type: object
>> +    description: Digital filter path child node
>> +
>> +    properties:
>> +      compatible:
>> +        enum:
>> +          - st,stm32mp25-mdf-dmic
>> +          - st,stm32mp25-mdf-adc
>> +
>> +      reg:
>> +        description: Specify the MDF filter instance
>> +        maxItems: 1
>> +
>> +      interrupts:
>> +        maxItems: 1
>> +
>> +      clocks:
>> +        minItems: 1
>> +        description: Internal clock used for MDF digital processing and control blocks.
>> +
>> +      clock-names:
>> +        items:
>> +          - const: ker_ck
>> +
>> +      dmas:
>> +        maxItems: 1
>> +
>> +      dma-names:
>> +        items:
>> +          - const: rx
>> +
>> +      "#io-channel-cells":
>> +        const: 1
>> +
>> +      '#address-cells':
>> +        const: 1
>> +
>> +      '#size-cells':
>> +        const: 0
>> +
>> +      st,cic-mode:
>> +        description: |
>> +          Cascaded-integrator-comb (CIC) filter configuration
>> +          - 0: MCIC & ACIC filters in FastSinc mode
>> +          - [1-3]: MCIC & ACIC filters in Sinc mode order 1 to 3
>> +          - [4-5]: Single CIC filter in Sinc mode order 4 to 5
>> +          For audio purpose it is recommended to use CIC Sinc4 or Sinc5
>> +          This property is mandatory for filter 0 or filters not used in interleave mode.
>> +        $ref: /schemas/types.yaml#/definitions/uint32
>> +        minimum: 0
>> +        maximum: 5
>> +
>> +      st,delay:
>> +        description: Filter delay in samples
>> +        $ref: /schemas/types.yaml#/definitions/uint32
>> +        maximum: 127
>> +
>> +      st,rs-filter-bypass:
>> +        description: Bypass RSFLT reshaping filter.
>> +        $ref: /schemas/types.yaml#/definitions/flag
>> +
>> +      st,hpf-filter-cutoff-bp:
>> +        description: |
>> +          High Pass Filter (HPF) cut-off frequency expressed as a fraction of the PCM sampling rate.
>> +          Cut-off frequency = st,hpf-filter-cutoff-bp x Fpcm / 10000.
>> +          If this property is not defined the HPF is disabled.
>> +        enum: [625, 1250, 2500, 9500]
>> +
>> +      st,sync:
>> +        description:
>> +          Synchronize to another filter.
>> +          Must contain the phandle of the filter providing the synchronization.
>> +        allOf:
>> +          - $ref: /schemas/types.yaml#/definitions/phandle-array
>> +          - maxItems: 1
>> +
>> +      st,sitf:
>> +        $ref: /schemas/types.yaml#/definitions/phandle-array
>> +        items:
>> +          - items:
>> +              - description: Phandle of the serial interface connected to the digital filter
>> +              - description: |
>> +                  The phandle's argument selects the bitstream on the falling or rising edge
>> +                  of the serial interface clock:
>> +                  - 0: rising edge
>> +                  - 1: falling edge
>> +                enum: [0, 1]
>> +                default: 0
>> +        description:
>> +          Should be phandle/bitstream pair.
>> +
>> +    required:
>> +      - compatible
>> +      - reg
>> +      - interrupts
>> +      - dmas
>> +      - dma-names
>> +      - "#io-channel-cells"
>> +      - "#address-cells"
>> +      - "#size-cells"
>> +      - st,sitf
>> +
>> +    unevaluatedProperties: false
>> +
>> +    patternProperties:
>> +      "^channel@([0-7])$":
>> +        type: object
>> +        $ref: adc.yaml
>> +        description: Represents the external channel which is connected to the MDF.
>> +
>> +        properties:
>> +          reg:
>> +            maximum: 7
>> +
>> +          io-backends:
>> +            description:
>> +              Used to pipe external sigma delta modulator or internal ADC backend to MDF
>> +              channel.
>> +            maxItems: 1
>> +
>> +        required:
>> +          - reg
>> +
>> +        unevaluatedProperties: false
>> +
>> +    allOf:
>> +      - if:
>> +          properties:
>> +            compatible:
>> +              contains:
>> +                const: st,stm32mp25-mdf-adc
>> +
>> +        then:
>> +          patternProperties:
>> +            "^channel@[0-7]$":
>> +              required:
>> +                - io-backends
>> +
>> +      - if:
>> +          properties:
>> +            compatible:
>> +              contains:
>> +                const: st,stm32mp25-mdf-dmic
>> +
>> +        then:
>> +          patternProperties:
>> +            "^mdf-dai+$":
>> +              type: object
>> +              description: child node
>> +
>> +              properties:
>> +                compatible:
>> +                  enum:
>> +                    - st,stm32mp25-mdf-dai
>> +
>> +                "#sound-dai-cells":
>> +                  const: 0
>> +
>> +                io-channels:
>> +                  description:
>> +                    From common IIO binding. Used to pipe external sigma delta
>> +                    modulator or internal ADC output to MDF channel.
>> +
>> +                power-domains:
>> +                  maxItems: 1
>> +
>> +                port:
>> +                  $ref: /schemas/sound/audio-graph-port.yaml#
>> +                  unevaluatedProperties: false
>> +
>> +              required:
>> +                - compatible
>> +                - "#sound-dai-cells"
>> +                - io-channels
>> +
>> +              additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +    mdf1: mdf@504d0000 {
>> +      compatible = "st,stm32mp25-mdf";
>> +      ranges = <0 0x504d0000 0x1000>;
>> +      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;
>> +      #address-cells = <1>;
>> +      #size-cells = <1>;
>> +      clocks = <&rcc CK_KER_MDF1>;
>> +      clock-names = "ker_ck";
>> +      clock-ranges;
>> +      #clock-cells = <1>;
>> +      clock-output-names = "cck0", "cck1";
>> +      clock-frequency = <2048000>;
>> +
>> +      sitf5: sitf@300 {
>> +        compatible = "st,stm32mp25-sitf-mdf";
>> +        reg = <0x300 0x4>;
>> +        st,sitf-mode = "spi";
>> +        clocks = <&mdf1 0>;
>> +      };
>> +
>> +      filter0: filter@84 {
>> +        compatible = "st,stm32mp25-mdf-dmic";
>> +        reg = <0x84 0x70>;
>> +        #io-channel-cells = <1>;
>> +        interrupts = <GIC_SPI 184 IRQ_TYPE_LEVEL_HIGH>;
>> +        dmas = <&hpdma 63 0x63 0x12 0>;
>> +        dma-names = "rx";
>> +        st,cic-mode = <5>;
>> +        st,sitf = <&sitf5 0>;
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +
>> +        channel@0 {
>> +          reg = <0>;
>> +        };
>> +
>> +        asoc_pdm0: mdf-dai {
>> +          compatible = "st,stm32mp25-mdf-dai";
>> +          #sound-dai-cells = <0>;
>> +          io-channels = <&filter0 0>;
>> +        };
>> +      };
>> +
>> +      filter1: filter@104  {
>> +        compatible = "st,stm32mp25-mdf-adc";
>> +        reg = <0x104 0x70>;
>> +        #io-channel-cells = <1>;
>> +        interrupts = <GIC_SPI 185 IRQ_TYPE_LEVEL_HIGH>;
>> +        dmas = <&hpdma 64 0x63 0x12 0>;
>> +        dma-names = "rx";
>> +        st,cic-mode = <2>;
>> +        st,sitf = <&sitf5 1>;
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +
>> +        channel@1 {
>> +          reg = <1>;
>> +          settling-time-us = <1000>;
>> +          io-backends = <&sd_adc1>;
>> +        };
>> +      };
>> +    };
>> +
>> +...
>> -- 
>> 2.43.0
>>

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Rob Herring]

On Wed, Oct 07, 2026 at 11:01:28AM +0200, Olivier MOYSAN wrote:
> Hi Conor,
> 
> Thanks for the review
> 
> On 10/1/26 20:32, Conor Dooley wrote:
> > On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
> > > Add bindings that describes STM32 MDF settings to support
> > > digital filtering for Pulse Density Modulation (PDM) microphones
> > > and analog sigma delta modulators.
> > > 
> > > Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> > > ---
> > >   .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
> > >   1 file changed, 383 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> > > new file mode 100644
> > > index 000000000000..f2fbc3e150e8
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> > > @@ -0,0 +1,383 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
> > > +
> > > +maintainers:
> > > +  - Olivier Moysan <olivier.moysan@foss.st.com>
> > > +
> > > +description: |
> > > +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
> > > +  interface external sigma delta modulators to STM32 micro controllers.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - st,stm32mp25-mdf
> > > +      - st,stm32mp23-mdf
> > > +
> > > +  reg:
> > > +    minItems: 1
> > > +    maxItems: 2
> > 
> > This needs an items list here. The size of the regions seems like crap
> > to begin with...
> > 
> > > +
> > > +  clocks:
> > > +    maxItems: 1
> > > +
> > > +  clock-names:
> > > +    description: Internal clock used for MDF digital processing.
> > > +    items:
> > > +      - const: ker_ck
> > 
> > This is pointless when you only have one.
> > 
> 
> I agree that it could be dropped. However, it is useful for using
> devm_regmap_init_mmio_clk.

I don't know what that function is/does, but that's not justification 
for bindings. Maybe you need a helper that handles a single clock. Or 
that function could take a NULL string for single clock? 

> 
> > > +
> > > +  "#clock-cells":
> > > +    enum: [0, 1]
> > 
> > Why is this not fixed? Also why are parts of your own device consuming
> > the clocks?
> > 
> > > +
> > > +  clock-output-names:
> > > +    description: |
> > > +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
> > > +      but can be gated independently to save power.
> > > +    minItems: 1
> > > +    maxItems: 2
> > > +    oneOf:
> > > +      - items:
> > > +          - const: cck0
> > > +      - items:
> > > +          - const: cck1
> > > +      - items:
> > > +          - const: cck0
> > > +          - const: cck1
> > > +
> > > +  clock-frequency:
> > > +    description: |
> > > +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
> > > +      The frequency must be a multiple of the "ker_ck" clock frequency.
> > > +    maximum: 25000000
> > 
> > Should not be needed, the consumers request what they need.
> > 
> 
> The CCKx clock frequency depends on the maximum rate supported by the sigma
> delta converters (for instance a digital mic) and the expected decimation
> ratio on the bitstream. Typically this determines the frequency on the SPI
> bus.
> This rate is defined statically and shared by the CCKx clocks. So IMHO, as
> this rate is unique, it can look strange to let the consumer define it.
> Moreover, it seems to me that clock-frequency is already used to configure
> the frequency of a provider in some other bindings.
> For instance: Documentation/devicetree/bindings/clock/silabs,si570.yaml
> So, it's not clear for me, what is the restriction on clock-frequency
> property.
> > > +
> > > +  ranges: true
> > > +
> > > +  clock-ranges: true
> > > +
> > > +  resets:
> > > +    maxItems: 1
> > > +
> > > +  reset-names:
> > > +    items:
> > > +      - const: mdf
> > > +
> > > +  access-controllers:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > > +    description: |
> > > +      Phandle to the rifsc device to check access right.
> > > +
> > > +  power-domains:
> > > +    maxItems: 1
> > > +
> > > +  st,interleave:
> > > +    description: |
> > > +      List of phandles of interleaved filters. The indexes of interleaved filters must be
> > > +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
> > > +      are muxed in a single channel and retrieved through the device associated to the filter 0.
> > > +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
> > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > 
> > No idea what these even are, but this is probably not the right way to
> > represent the relationship between devices. They're apparently ADCs, but
> > this is also an ADC so I'm not sure what's going on here at all.

I don't under it either, but regardless phandle-array needs constraints 
on the items. It's really a matrix with array of phandle+args arrays.

Rob

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Olivier MOYSAN]

Hi Rob,

On 10/7/26 15:47, Rob Herring wrote:
> On Wed, Oct 07, 2026 at 11:01:28AM +0200, Olivier MOYSAN wrote:
>> Hi Conor,
>>
>> Thanks for the review
>>
>> On 10/1/26 20:32, Conor Dooley wrote:
>>> On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
>>>> Add bindings that describes STM32 MDF settings to support
>>>> digital filtering for Pulse Density Modulation (PDM) microphones
>>>> and analog sigma delta modulators.
>>>>
>>>> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
>>>> ---
>>>>    .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
>>>>    1 file changed, 383 insertions(+)
>>>>    create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>>> new file mode 100644
>>>> index 000000000000..f2fbc3e150e8
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
>>>> @@ -0,0 +1,383 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
>>>> +
>>>> +maintainers:
>>>> +  - Olivier Moysan <olivier.moysan@foss.st.com>
>>>> +
>>>> +description: |
>>>> +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
>>>> +  interface external sigma delta modulators to STM32 micro controllers.
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    enum:
>>>> +      - st,stm32mp25-mdf
>>>> +      - st,stm32mp23-mdf
>>>> +
>>>> +  reg:
>>>> +    minItems: 1
>>>> +    maxItems: 2
>>>
>>> This needs an items list here. The size of the regions seems like crap
>>> to begin with...
>>>
>>>> +
>>>> +  clocks:
>>>> +    maxItems: 1
>>>> +
>>>> +  clock-names:
>>>> +    description: Internal clock used for MDF digital processing.
>>>> +    items:
>>>> +      - const: ker_ck
>>>
>>> This is pointless when you only have one.
>>>
>>
>> I agree that it could be dropped. However, it is useful for using
>> devm_regmap_init_mmio_clk.
> 
> I don't know what that function is/does, but that's not justification
> for bindings. Maybe you need a helper that handles a single clock. Or
> that function could take a NULL string for single clock?
> 

Ok. I will drop this clock, and use a helper to replace 
devm_regmap_init_mmio_clk api calls.

>>
>>>> +
>>>> +  "#clock-cells":
>>>> +    enum: [0, 1]
>>>
>>> Why is this not fixed? Also why are parts of your own device consuming
>>> the clocks?
>>>
>>>> +
>>>> +  clock-output-names:
>>>> +    description: |
>>>> +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
>>>> +      but can be gated independently to save power.
>>>> +    minItems: 1
>>>> +    maxItems: 2
>>>> +    oneOf:
>>>> +      - items:
>>>> +          - const: cck0
>>>> +      - items:
>>>> +          - const: cck1
>>>> +      - items:
>>>> +          - const: cck0
>>>> +          - const: cck1
>>>> +
>>>> +  clock-frequency:
>>>> +    description: |
>>>> +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
>>>> +      The frequency must be a multiple of the "ker_ck" clock frequency.
>>>> +    maximum: 25000000
>>>
>>> Should not be needed, the consumers request what they need.
>>>
>>
>> The CCKx clock frequency depends on the maximum rate supported by the sigma
>> delta converters (for instance a digital mic) and the expected decimation
>> ratio on the bitstream. Typically this determines the frequency on the SPI
>> bus.
>> This rate is defined statically and shared by the CCKx clocks. So IMHO, as
>> this rate is unique, it can look strange to let the consumer define it.
>> Moreover, it seems to me that clock-frequency is already used to configure
>> the frequency of a provider in some other bindings.
>> For instance: Documentation/devicetree/bindings/clock/silabs,si570.yaml
>> So, it's not clear for me, what is the restriction on clock-frequency
>> property.

Would you have any feedback regarding clock-frequency property usage ?

>>>> +
>>>> +  ranges: true
>>>> +
>>>> +  clock-ranges: true
>>>> +
>>>> +  resets:
>>>> +    maxItems: 1
>>>> +
>>>> +  reset-names:
>>>> +    items:
>>>> +      - const: mdf
>>>> +
>>>> +  access-controllers:
>>>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>>>> +    description: |
>>>> +      Phandle to the rifsc device to check access right.
>>>> +
>>>> +  power-domains:
>>>> +    maxItems: 1
>>>> +
>>>> +  st,interleave:
>>>> +    description: |
>>>> +      List of phandles of interleaved filters. The indexes of interleaved filters must be
>>>> +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
>>>> +      are muxed in a single channel and retrieved through the device associated to the filter 0.
>>>> +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
>>>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>>>
>>> No idea what these even are, but this is probably not the right way to
>>> represent the relationship between devices. They're apparently ADCs, but
>>> this is also an ADC so I'm not sure what's going on here at all.
> 
> I don't under it either, but regardless phandle-array needs constraints
> on the items. It's really a matrix with array of phandle+args arrays.
> 

What is expected for this property is a list of phandles (from 2 to 8)
For instance: st,interleave = <&filter0 &filter1>;

So, if I just consider the missing constraints, I need to add
     minItems: 2
     maxItems: 8
     items:
       maxItems: 1

Is this correct ?

> Rob

Best regards
Olivier

Re: [PATCH 1/3] dt-bindings: iio: adc: add bindings for stm32 mdf filter

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 20073 bytes --]

On Wed, Oct 07, 2026 at 11:01:28AM +0200, Olivier MOYSAN wrote:
> Hi Conor,
> 
> Thanks for the review
> 
> On 10/1/26 20:32, Conor Dooley wrote:
> > On Thu, Oct 01, 2026 at 04:56:45PM +0200, Olivier Moysan wrote:
> > > Add bindings that describes STM32 MDF settings to support
> > > digital filtering for Pulse Density Modulation (PDM) microphones
> > > and analog sigma delta modulators.
> > > 
> > > Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> > > ---
> > >   .../bindings/iio/adc/st,stm32-mdf-adc.yaml    | 383 ++++++++++++++++++
> > >   1 file changed, 383 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> > > new file mode 100644
> > > index 000000000000..f2fbc3e150e8
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-mdf-adc.yaml
> > > @@ -0,0 +1,383 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/iio/adc/st,stm32-mdf-adc.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: STMicroelectronics STM32 Multi-function Digital Filter (MDF) ADC
> > > +
> > > +maintainers:
> > > +  - Olivier Moysan <olivier.moysan@foss.st.com>
> > > +
> > > +description: |
> > > +  STM32 MDF ADC is a sigma delta analog-to-digital converter dedicated to
> > > +  interface external sigma delta modulators to STM32 micro controllers.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - st,stm32mp25-mdf
> > > +      - st,stm32mp23-mdf
> > > +
> > > +  reg:
> > > +    minItems: 1
> > > +    maxItems: 2
> > 
> > This needs an items list here. The size of the regions seems like crap
> > to begin with...
> > 
> > > +
> > > +  clocks:
> > > +    maxItems: 1
> > > +
> > > +  clock-names:
> > > +    description: Internal clock used for MDF digital processing.
> > > +    items:
> > > +      - const: ker_ck
> > 
> > This is pointless when you only have one.
> > 
> 
> I agree that it could be dropped. However, it is useful for using
> devm_regmap_init_mmio_clk.

Ah, because that function if you pass NULL to it, it doesn't mean no
string, it means no clock.

> 
> > > +
> > > +  "#clock-cells":
> > > +    enum: [0, 1]
> > 
> > Why is this not fixed? Also why are parts of your own device consuming
> > the clocks?

Reading the docs, this has to be 1, you have two clocks?

Not sure why you skipped this and skipped explaining why you are
consuming your own clocks.

> > > +  clock-output-names:
> > > +    description: |
> > > +      CCK0 and CCK1 are optional output clocks, which share the same clock frequency,
> > > +      but can be gated independently to save power.
> > > +    minItems: 1
> > > +    maxItems: 2
> > > +    oneOf:
> > > +      - items:
> > > +          - const: cck0
> > > +      - items:
> > > +          - const: cck1
> > > +      - items:
> > > +          - const: cck0
> > > +          - const: cck1
> > > +
> > > +  clock-frequency:
> > > +    description: |
> > > +      Common clock frequency (Hz) for CCK0 and CCK1 output clocks.
> > > +      The frequency must be a multiple of the "ker_ck" clock frequency.
> > > +    maximum: 25000000
> > 
> > Should not be needed, the consumers request what they need.
> > 
> 
> The CCKx clock frequency depends on the maximum rate supported by the sigma
> delta converters (for instance a digital mic) and the expected decimation
> ratio on the bitstream. Typically this determines the frequency on the SPI
> bus.
> This rate is defined statically and shared by the CCKx clocks. So IMHO, as
> this rate is unique, it can look strange to let the consumer define it.
> Moreover, it seems to me that clock-frequency is already used to configure
> the frequency of a provider in some other bindings.
> For instance: Documentation/devicetree/bindings/clock/silabs,si570.yaml

This is a binding from the age of antiquity, using it to justify your
use is actually harming your argument rather than helping. Your clock
consumers should be providing the information about what the rate should
be, and if you need to do this in dt you can use assigned-clock-rates.

> So, it's not clear for me, what is the restriction on clock-frequency
> property.
> > > +
> > > +  ranges: true
> > > +
> > > +  clock-ranges: true
> > > +
> > > +  resets:
> > > +    maxItems: 1
> > > +
> > > +  reset-names:
> > > +    items:
> > > +      - const: mdf

Same applies here as to the clock names fwiw.

> > > +
> > > +  access-controllers:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > > +    description: |
> > > +      Phandle to the rifsc device to check access right.
> > > +
> > > +  power-domains:
> > > +    maxItems: 1
> > > +
> > > +  st,interleave:
> > > +    description: |
> > > +      List of phandles of interleaved filters. The indexes of interleaved filters must be
> > > +      consecutives starting from 0 (i.e in range [0..N]). The samples from interleaved filters
> > > +      are muxed in a single channel and retrieved through the device associated to the filter 0.
> > > +      The filters 1..N have to be enabled, but inherit their configuration from filter 0.
> > > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > 
> > No idea what these even are, but this is probably not the right way to
> > represent the relationship between devices. They're apparently ADCs, but
> > this is also an ADC so I'm not sure what's going on here at all.

Yeah, after more thought this should not be done like this at all,
especially if these filters the phandle point to are part of this device
itself, which I suspect they are. If that's the case, you don't need
phandles to even do this, you just need an int that says what N is.

> > 
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +  - ranges
> > > +  - clocks
> > > +  - clock-names
> > > +  - clock-ranges
> > > +  - "#address-cells"
> > > +  - "#size-cells"
> > > +
> > > +additionalProperties: false
> > > +
> > > +patternProperties:
> > > +  "^sitf@[0-9]+$":
> > > +    type: object
> > > +    description: Serial interface child node
> > 
> > Why is this a child node at all?
> > Probably not worth reviewing more without a link to the docs for this
> > device so I can figure out what on earth is going on!
> > 
> 
> The MDF is a digital filter for sigma-delta bitstreams, rather than the
> analog-to-digital converter itself.
> 
> Here is the link to STM32MP25 reference manuel
> https://www.st.com/resource/en/reference_manual/rm0457-stm32mp2325xx-advanced-armbased-3264bit-mpus-stmicroelectronics.pdf
> Chapter 45: Multi-function digital filter (MDF)
> 
> On STMP32MP25 SoC, the MDF provides 8 serial interfaces (SITF) and 8 digital
> filters (DFLT) which can be connected through a multiplexer.
> 
> Below is a schematic view of typical applications targeted by this
> peripheral
> 
> 
> Audio use case:
> 
> 		mdf
>             +-------------------------------------+
> +------+    | +------+    +------+    +------+    |
> | dmic | -> | | sitf | -> | mux  | -> | dflt | -- | -> audio device
> +------+    | +------+    +------+    +------+    |
>             +-------------------------------------+
> 
> For instance, in an audio use case the serial interface can be configured to
> provide the clock to the digital microphone (cck0, cck1 or both) at a common
> predefined rate, and to retrieve the PDM samples.
> The serial interface provides this samples to a digital filter, which
> delivers PCM samples on its output.
> 
> 
> Analog use case:
> 
> 		mdf
>               +-------------------------------------+
> +--------+    | +------+    +------+    +------+    |
> | sd adc | -> | | sitf | -> | mux  | -> | dflt | -- | -> iio device
> +--------+    | +------+    +------+    +------+    |
>               +-------------------------------------+


So, looking at the docs and a brief chat with Jonathan about this
device, I believe you've got things backwards and this is actually the backend,
and the adc should be the one populating the io-backends property
pointing to this device. You should have io-backend-cells, and I assume
that there should be a cell for the adc to select which dlft it is connected
to.

I think all of these child nodes should just get deleted - all your
devices here seem completely fake, since you've got stuff that's only a
single word wide. With that, you could also throw away these mickey
mouse nodes with sound-dai-cels of 0, and use 1 instead, with that cell
again determining which dlft is in use.

The only child node I can really thing of any justification for here is
channels - albeit not adc channels since this is not an adc - so that
you can individually configure a dlft using those channel nodes.

These serial inputs, what is the source for the data that is ever
actually sent there? I am assuming it's effectively another IIO device,
just not the onboard adc? Are the outputs exposed on pins on the
package?

I would encourage you to remodel this system, where this device is the
backend and also try to get rid of as much of the consuming your own
clock as possible. Certainly consuming ker_clk should never be required.
It's hard to reason about what should happen with the serial interface
clocks, when I have no idea what the input/data source device actually
is in those cases. Being a clock controller does make sense, because the
device exposes CCK0/1 to the outside world, it's the internal routing to
the SITF blocks that I am not sure how to deal with. A ouroboros device
that is consuming a clock it provides is not really a done thing,
hopefully the IIO guys can tell you how these kinds of things are
typically done here, since I'm sure there's plenty of other devices
that have some sort of ability to change the clock source for a channel.

Probably you need to add two optional input clocks to this device, since
mdf_cck0/1 can be inputs too?

Let me know if any of this feedback is intractable stuff, and maybe hang
on for someone like David or Jonathan to provide some review before
going about a significant rework. It's worth bearing in mind that I am a
binding reviewer and not a domain expert in ADCs etc.

Thanks,
Conor.

> > > +
> > > +    properties:
> > > +      compatible:
> > > +        enum:
> > > +          - st,stm32mp25-sitf-mdf
> > > +
> > > +      reg:
> > > +        description: Specify the SITF serial interface instance
> > > +        maxItems: 1
> > > +
> > > +      clocks:
> > > +        description: |
> > > +          Serial interface clock (optional depending on interface mode)
> > > +        maxItems: 1
> > > +
> > > +      st,sitf-mode:
> > > +        description: |
> > > +          Select serial interface protocol
> > > +          - spi: SPI mode
> > > +          - lf_spi: low frequency SPI mode for low power applications
> > > +        $ref: /schemas/types.yaml#/definitions/string
> > > +        enum:
> > > +          - spi
> > > +          - lf_spi
> > > +
> > > +    required:
> > > +      - reg
> > > +      - st,sitf-mode
> > > +
> > > +    additionalProperties: false
> > > +
> > > +  "^filter@[0-9]+$":
> > > +    type: object
> > > +    description: Digital filter path child node
> > > +
> > > +    properties:
> > > +      compatible:
> > > +        enum:
> > > +          - st,stm32mp25-mdf-dmic
> > > +          - st,stm32mp25-mdf-adc
> > > +
> > > +      reg:
> > > +        description: Specify the MDF filter instance
> > > +        maxItems: 1
> > > +
> > > +      interrupts:
> > > +        maxItems: 1
> > > +
> > > +      clocks:
> > > +        minItems: 1
> > > +        description: Internal clock used for MDF digital processing and control blocks.
> > > +
> > > +      clock-names:
> > > +        items:
> > > +          - const: ker_ck
> > > +
> > > +      dmas:
> > > +        maxItems: 1
> > > +
> > > +      dma-names:
> > > +        items:
> > > +          - const: rx
> > > +
> > > +      "#io-channel-cells":
> > > +        const: 1
> > > +
> > > +      '#address-cells':
> > > +        const: 1
> > > +
> > > +      '#size-cells':
> > > +        const: 0
> > > +
> > > +      st,cic-mode:
> > > +        description: |
> > > +          Cascaded-integrator-comb (CIC) filter configuration
> > > +          - 0: MCIC & ACIC filters in FastSinc mode
> > > +          - [1-3]: MCIC & ACIC filters in Sinc mode order 1 to 3
> > > +          - [4-5]: Single CIC filter in Sinc mode order 4 to 5
> > > +          For audio purpose it is recommended to use CIC Sinc4 or Sinc5
> > > +          This property is mandatory for filter 0 or filters not used in interleave mode.
> > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > +        minimum: 0
> > > +        maximum: 5
> > > +
> > > +      st,delay:
> > > +        description: Filter delay in samples
> > > +        $ref: /schemas/types.yaml#/definitions/uint32
> > > +        maximum: 127
> > > +
> > > +      st,rs-filter-bypass:
> > > +        description: Bypass RSFLT reshaping filter.
> > > +        $ref: /schemas/types.yaml#/definitions/flag
> > > +
> > > +      st,hpf-filter-cutoff-bp:
> > > +        description: |
> > > +          High Pass Filter (HPF) cut-off frequency expressed as a fraction of the PCM sampling rate.
> > > +          Cut-off frequency = st,hpf-filter-cutoff-bp x Fpcm / 10000.
> > > +          If this property is not defined the HPF is disabled.
> > > +        enum: [625, 1250, 2500, 9500]
> > > +
> > > +      st,sync:
> > > +        description:
> > > +          Synchronize to another filter.
> > > +          Must contain the phandle of the filter providing the synchronization.
> > > +        allOf:
> > > +          - $ref: /schemas/types.yaml#/definitions/phandle-array
> > > +          - maxItems: 1
> > > +
> > > +      st,sitf:
> > > +        $ref: /schemas/types.yaml#/definitions/phandle-array
> > > +        items:
> > > +          - items:
> > > +              - description: Phandle of the serial interface connected to the digital filter
> > > +              - description: |
> > > +                  The phandle's argument selects the bitstream on the falling or rising edge
> > > +                  of the serial interface clock:
> > > +                  - 0: rising edge
> > > +                  - 1: falling edge
> > > +                enum: [0, 1]
> > > +                default: 0
> > > +        description:
> > > +          Should be phandle/bitstream pair.
> > > +
> > > +    required:
> > > +      - compatible
> > > +      - reg
> > > +      - interrupts
> > > +      - dmas
> > > +      - dma-names
> > > +      - "#io-channel-cells"
> > > +      - "#address-cells"
> > > +      - "#size-cells"
> > > +      - st,sitf
> > > +
> > > +    unevaluatedProperties: false
> > > +
> > > +    patternProperties:
> > > +      "^channel@([0-7])$":
> > > +        type: object
> > > +        $ref: adc.yaml
> > > +        description: Represents the external channel which is connected to the MDF.
> > > +
> > > +        properties:
> > > +          reg:
> > > +            maximum: 7
> > > +
> > > +          io-backends:
> > > +            description:
> > > +              Used to pipe external sigma delta modulator or internal ADC backend to MDF
> > > +              channel.
> > > +            maxItems: 1

> > > +
> > > +        required:
> > > +          - reg
> > > +
> > > +        unevaluatedProperties: false
> > > +
> > > +    allOf:
> > > +      - if:
> > > +          properties:
> > > +            compatible:
> > > +              contains:
> > > +                const: st,stm32mp25-mdf-adc
> > > +
> > > +        then:
> > > +          patternProperties:
> > > +            "^channel@[0-7]$":
> > > +              required:
> > > +                - io-backends
> > > +
> > > +      - if:
> > > +          properties:
> > > +            compatible:
> > > +              contains:
> > > +                const: st,stm32mp25-mdf-dmic
> > > +
> > > +        then:
> > > +          patternProperties:
> > > +            "^mdf-dai+$":
> > > +              type: object
> > > +              description: child node
> > > +
> > > +              properties:
> > > +                compatible:
> > > +                  enum:
> > > +                    - st,stm32mp25-mdf-dai
> > > +
> > > +                "#sound-dai-cells":
> > > +                  const: 0
> > > +
> > > +                io-channels:
> > > +                  description:
> > > +                    From common IIO binding. Used to pipe external sigma delta
> > > +                    modulator or internal ADC output to MDF channel.
> > > +
> > > +                power-domains:
> > > +                  maxItems: 1
> > > +
> > > +                port:
> > > +                  $ref: /schemas/sound/audio-graph-port.yaml#
> > > +                  unevaluatedProperties: false
> > > +
> > > +              required:
> > > +                - compatible
> > > +                - "#sound-dai-cells"
> > > +                - io-channels
> > > +
> > > +              additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
> > > +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> > > +    mdf1: mdf@504d0000 {
> > > +      compatible = "st,stm32mp25-mdf";
> > > +      ranges = <0 0x504d0000 0x1000>;
> > > +      reg = <0x504d0000 0x8>, <0x504d0ff0 0x10>;
> > > +      #address-cells = <1>;
> > > +      #size-cells = <1>;
> > > +      clocks = <&rcc CK_KER_MDF1>;
> > > +      clock-names = "ker_ck";
> > > +      clock-ranges;
> > > +      #clock-cells = <1>;
> > > +      clock-output-names = "cck0", "cck1";
> > > +      clock-frequency = <2048000>;
> > > +
> > > +      sitf5: sitf@300 {
> > > +        compatible = "st,stm32mp25-sitf-mdf";
> > > +        reg = <0x300 0x4>;
> > > +        st,sitf-mode = "spi";
> > > +        clocks = <&mdf1 0>;
> > > +      };
> > > +
> > > +      filter0: filter@84 {
> > > +        compatible = "st,stm32mp25-mdf-dmic";
> > > +        reg = <0x84 0x70>;
> > > +        #io-channel-cells = <1>;
> > > +        interrupts = <GIC_SPI 184 IRQ_TYPE_LEVEL_HIGH>;
> > > +        dmas = <&hpdma 63 0x63 0x12 0>;
> > > +        dma-names = "rx";
> > > +        st,cic-mode = <5>;
> > > +        st,sitf = <&sitf5 0>;
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +
> > > +        channel@0 {
> > > +          reg = <0>;
> > > +        };
> > > +
> > > +        asoc_pdm0: mdf-dai {
> > > +          compatible = "st,stm32mp25-mdf-dai";
> > > +          #sound-dai-cells = <0>;
> > > +          io-channels = <&filter0 0>;
> > > +        };
> > > +      };
> > > +
> > > +      filter1: filter@104  {
> > > +        compatible = "st,stm32mp25-mdf-adc";
> > > +        reg = <0x104 0x70>;
> > > +        #io-channel-cells = <1>;
> > > +        interrupts = <GIC_SPI 185 IRQ_TYPE_LEVEL_HIGH>;
> > > +        dmas = <&hpdma 64 0x63 0x12 0>;
> > > +        dma-names = "rx";
> > > +        st,cic-mode = <2>;
> > > +        st,sitf = <&sitf5 1>;
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +
> > > +        channel@1 {
> > > +          reg = <1>;
> > > +          settling-time-us = <1000>;
> > > +          io-backends = <&sd_adc1>;
> > > +        };
> > > +      };
> > > +    };
> > > +
> > > +...
> > > -- 
> > > 2.43.0
> > > 
> 

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