[PATCH v3 0/8] iio: adc: dfsdm: add scaling support

[PATCH v3 0/8] iio: adc: dfsdm: add scaling support

[Olivier Moysan]

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

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

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

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

Backward compatibility is maintained through legacy support.

This series extends the backend framework with the following APIs:
- iio_backend_read_raw:
	This API is intented to retrieve channel attributes from the
	backend. It is based on IIO framework read_raw API.
- iio_backend_read_scale / iio_backend_read_offset
	Dedicated APIs to read scale and offset channel values.
- iio_backend_disable / iio_backend_enable:
	backend enable/disable to be used for PM management
- devm_iio_backend_fwnode_get
	Intended for parsing DT subnodes to allow generic channel binding
	support, as generic channel DT nodes are not populated as devices.

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

Changes in v2:
- Update enable/disable backend API
- Rename devm_iio_backend_subnode_get(), as devm_iio_backend_fwnode_get()
- Update iio_backend_read_raw() prototype to fully match IIO framework
  read_raw callback prototype.
- Change st,adc-channel-type property name and type in DFSDM binding
- Remove sd-backend and rename ads1201 compatibles in SD binding

Changes in v3:
- Add iio_backend_read_scale and iio_backend_read_offset
- Remove sd-backend compatible. Adapt existing sd modulator driver and
  binding to support backend topology.
- Misc corrections in DFSDM binding & minor changes in DFSDM driver

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

 .../iio/adc/sigma-delta-modulator.yaml        |  24 +-
 .../bindings/iio/adc/st,stm32-dfsdm-adc.yaml  | 153 ++++++++-
 drivers/iio/adc/Kconfig                       |   2 +
 drivers/iio/adc/sd_adc_modulator.c            |  92 +++++-
 drivers/iio/adc/stm32-dfsdm-adc.c             | 298 +++++++++++++++---
 drivers/iio/industrialio-backend.c            | 111 ++++++-
 include/linux/iio/backend.h                   |  11 +-
 7 files changed, 626 insertions(+), 65 deletions(-)


base-commit: 529d2e1900642eba6df28307e26e19793e227546
-- 
2.25.1

[PATCH v3 1/8] iio: add read scale and offset services to iio backend framework

[Olivier Moysan]

Add iio_backend_read_scale() and iio_backend_read_offset() services
to read channel scale and offset from an IIO backbend device.

Also add a read_raw callback which replicates the read_raw callback of
the IIO framework, and is intended to request miscellaneous channel
attributes from the backend device.
Both scale and offset helpers use this callback.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
---
 drivers/iio/industrialio-backend.c | 30 ++++++++++++++++++++++++++++++
 include/linux/iio/backend.h        |  7 ++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index efe05be284b6..1d3d6dbdcc4e 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -357,6 +357,36 @@ int devm_iio_backend_request_buffer(struct device *dev,
 }
 EXPORT_SYMBOL_NS_GPL(devm_iio_backend_request_buffer, IIO_BACKEND);
 
+/**
+ * iio_backend_read_scale - Request channel scale from the IIO backend.
+ * @back:	Backend device
+ * @chan:	IIO channel reference
+ * @scale:	returned scale value
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int iio_backend_read_scale(struct iio_backend *back, struct iio_chan_spec const *chan, int *scale)
+{
+	return iio_backend_op_call(back, read_raw, chan, scale, 0, IIO_CHAN_INFO_SCALE);
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_read_scale, IIO_BACKEND);
+
+/**
+ * iio_backend_read_offset - Request channel offset from the IIO backend.
+ * @back:	Backend device
+ * @chan:	IIO channel reference
+ * @offset:	returned offset value
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int iio_backend_read_offset(struct iio_backend *back, struct iio_chan_spec const *chan, int *offset)
+{
+	return iio_backend_op_call(back, read_raw, chan, offset, 0, IIO_CHAN_INFO_OFFSET);
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_read_offset, IIO_BACKEND);
+
 static struct iio_backend *iio_backend_from_indio_dev_parent(const struct device *dev)
 {
 	struct iio_backend *back = ERR_PTR(-ENODEV), *iter;
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 8099759d7242..cbad233ae9f2 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -81,6 +81,7 @@ enum iio_backend_sample_trigger {
  * @extend_chan_spec: Extend an IIO channel.
  * @ext_info_set: Extended info setter.
  * @ext_info_get: Extended info getter.
+ * @read_raw: Read a channel attribute from a backend device
  **/
 struct iio_backend_ops {
 	int (*enable)(struct iio_backend *back);
@@ -113,6 +114,8 @@ struct iio_backend_ops {
 			    const char *buf, size_t len);
 	int (*ext_info_get)(struct iio_backend *back, uintptr_t private,
 			    const struct iio_chan_spec *chan, char *buf);
+	int (*read_raw)(struct iio_backend *back, struct iio_chan_spec const *chan, int *val,
+			int *val2, long mask);
 };
 
 int iio_backend_chan_enable(struct iio_backend *back, unsigned int chan);
@@ -141,7 +144,9 @@ ssize_t iio_backend_ext_info_set(struct iio_dev *indio_dev, uintptr_t private,
 				 const char *buf, size_t len);
 ssize_t iio_backend_ext_info_get(struct iio_dev *indio_dev, uintptr_t private,
 				 const struct iio_chan_spec *chan, char *buf);
-
+int iio_backend_read_scale(struct iio_backend *back, struct iio_chan_spec const *chan, int *scale);
+int iio_backend_read_offset(struct iio_backend *back, struct iio_chan_spec const *chan,
+			    int *offset);
 int iio_backend_extend_chan_spec(struct iio_dev *indio_dev,
 				 struct iio_backend *back,
 				 struct iio_chan_spec *chan);
-- 
2.25.1

[PATCH v3 2/8] iio: add enable and disable services to iio backend framework

[Olivier Moysan]

Add iio_backend_disable() and iio_backend_enable() APIs to allow
IIO backend consumer to request backend disabling and enabling.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
---
 drivers/iio/industrialio-backend.c | 25 ++++++++++++++++++++++++-
 include/linux/iio/backend.h        |  2 ++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index 1d3d6dbdcc4e..bb6aac68979f 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -146,6 +146,29 @@ static void __iio_backend_disable(void *back)
 	iio_backend_void_op_call(back, disable);
 }
 
+/**
+ * iio_backend_disable - Backend disable
+ * @back: Backend device
+ */
+void iio_backend_disable(struct iio_backend *back)
+{
+	__iio_backend_disable(back);
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_disable, IIO_BACKEND);
+
+/**
+ * iio_backend_enable - Backend enable
+ * @back: Backend device
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int iio_backend_enable(struct iio_backend *back)
+{
+	return iio_backend_op_call(back, enable);
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_enable, IIO_BACKEND);
+
 /**
  * devm_iio_backend_enable - Device managed backend enable
  * @dev: Consumer device for the backend
@@ -158,7 +181,7 @@ int devm_iio_backend_enable(struct device *dev, struct iio_backend *back)
 {
 	int ret;
 
-	ret = iio_backend_op_call(back, enable);
+	ret = iio_backend_enable(back);
 	if (ret)
 		return ret;
 
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index cbad233ae9f2..696997f2c0d6 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -121,6 +121,8 @@ struct iio_backend_ops {
 int iio_backend_chan_enable(struct iio_backend *back, unsigned int chan);
 int iio_backend_chan_disable(struct iio_backend *back, unsigned int chan);
 int devm_iio_backend_enable(struct device *dev, struct iio_backend *back);
+int iio_backend_enable(struct iio_backend *back);
+void iio_backend_disable(struct iio_backend *back);
 int iio_backend_data_format_set(struct iio_backend *back, unsigned int chan,
 				const struct iio_backend_data_fmt *data);
 int iio_backend_data_source_set(struct iio_backend *back, unsigned int chan,
-- 
2.25.1

[PATCH v3 3/8] iio: add child nodes support in iio backend framework

[Olivier Moysan]

Add an API to support IIO generic channels binding:
http://devicetree.org/schemas/iio/adc/adc.yaml#
This new API is needed, as generic channel DT node isn't populated as a
device.
Add devm_iio_backend_fwnode_get() to allow an IIO device backend
consumer to reference backend phandles in its child nodes.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
---
 drivers/iio/industrialio-backend.c | 56 +++++++++++++++++++++---------
 include/linux/iio/backend.h        |  2 ++
 2 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index bb6aac68979f..522765c7784f 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -586,19 +586,10 @@ static int __devm_iio_backend_get(struct device *dev, struct iio_backend *back)
 	return 0;
 }
 
-/**
- * devm_iio_backend_get - Device managed backend device get
- * @dev: Consumer device for the backend
- * @name: Backend name
- *
- * Get's the backend associated with @dev.
- *
- * RETURNS:
- * A backend pointer, negative error pointer otherwise.
- */
-struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
+static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, const char *name,
+							 struct fwnode_handle *fwnode)
 {
-	struct fwnode_handle *fwnode;
+	struct fwnode_handle *fwnode_back;
 	struct iio_backend *back;
 	unsigned int index;
 	int ret;
@@ -613,17 +604,17 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
 		index = 0;
 	}
 
-	fwnode = fwnode_find_reference(dev_fwnode(dev), "io-backends", index);
+	fwnode_back = fwnode_find_reference(fwnode, "io-backends", index);
 	if (IS_ERR(fwnode))
 		return dev_err_cast_probe(dev, fwnode,
 					  "Cannot get Firmware reference\n");
 
 	guard(mutex)(&iio_back_lock);
 	list_for_each_entry(back, &iio_back_list, entry) {
-		if (!device_match_fwnode(back->dev, fwnode))
+		if (!device_match_fwnode(back->dev, fwnode_back))
 			continue;
 
-		fwnode_handle_put(fwnode);
+		fwnode_handle_put(fwnode_back);
 		ret = __devm_iio_backend_get(dev, back);
 		if (ret)
 			return ERR_PTR(ret);
@@ -631,11 +622,44 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
 		return back;
 	}
 
-	fwnode_handle_put(fwnode);
+	fwnode_handle_put(fwnode_back);
 	return ERR_PTR(-EPROBE_DEFER);
 }
+
+/**
+ * devm_iio_backend_get - Device managed backend device get
+ * @dev: Consumer device for the backend
+ * @name: Backend name
+ *
+ * Get's the backend associated with @dev.
+ *
+ * RETURNS:
+ * A backend pointer, negative error pointer otherwise.
+ */
+struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
+{
+	return __devm_iio_backend_fwnode_get(dev, name, dev_fwnode(dev));
+}
 EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get, IIO_BACKEND);
 
+/**
+ * devm_iio_backend_fwnode_get - Device managed backend firmware node get
+ * @dev: Consumer device for the backend
+ * @name: Backend name
+ * @fwnode: Firmware node of the backend consumer
+ *
+ * Get's the backend associated with a firmware node.
+ *
+ * RETURNS:
+ * A backend pointer, negative error pointer otherwise.
+ */
+struct iio_backend *devm_iio_backend_fwnode_get(struct device *dev, const char *name,
+						struct fwnode_handle *fwnode)
+{
+	return __devm_iio_backend_fwnode_get(dev, name, fwnode);
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_backend_fwnode_get, IIO_BACKEND);
+
 /**
  * __devm_iio_backend_get_from_fwnode_lookup - Device managed fwnode backend device get
  * @dev: Consumer device for the backend
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 696997f2c0d6..ec0d6a307c79 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -154,6 +154,8 @@ int iio_backend_extend_chan_spec(struct iio_dev *indio_dev,
 				 struct iio_chan_spec *chan);
 void *iio_backend_get_priv(const struct iio_backend *conv);
 struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name);
+struct iio_backend *devm_iio_backend_fwnode_get(struct device *dev, const char *name,
+						struct fwnode_handle *fwnode);
 struct iio_backend *
 __devm_iio_backend_get_from_fwnode_lookup(struct device *dev,
 					  struct fwnode_handle *fwnode);
-- 
2.25.1

[PATCH v3 4/8] dt-bindings: iio: dfsdm: move to backend framework

[Olivier Moysan]

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

Keep the legacy binding as deprecated for backward compatibility.

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

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

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

- Analog binding:

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

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

- Audio binding:

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

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 .../bindings/iio/adc/st,stm32-dfsdm-adc.yaml  | 153 +++++++++++++++++-
 1 file changed, 147 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml
index 2722edab1d9a..5a5bc8b96402 100644
--- a/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.yaml
@@ -102,9 +102,11 @@ patternProperties:
         items:
           minimum: 0
           maximum: 7
+        deprecated: true
 
       st,adc-channel-names:
         description: List of single-ended channel names.
+        deprecated: true
 
       st,filter-order:
         description: |
@@ -118,6 +120,12 @@ patternProperties:
       "#io-channel-cells":
         const: 1
 
+      '#address-cells':
+        const: 1
+
+      '#size-cells':
+        const: 0
+
       st,adc-channel-types:
         description: |
           Single-ended channel input type.
@@ -128,6 +136,7 @@ patternProperties:
         items:
           enum: [ SPI_R, SPI_F, MANCH_R, MANCH_F ]
         $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+        deprecated: true
 
       st,adc-channel-clk-src:
         description: |
@@ -139,6 +148,7 @@ patternProperties:
         items:
           enum: [ CLKIN, CLKOUT, CLKOUT_F, CLKOUT_R ]
         $ref: /schemas/types.yaml#/definitions/non-unique-string-array
+        deprecated: true
 
       st,adc-alt-channel:
         description:
@@ -147,6 +157,7 @@ patternProperties:
           If not set, channel n is connected to SPI input n.
           If set, channel n is connected to SPI input n + 1.
         type: boolean
+        deprecated: true
 
       st,filter0-sync:
         description:
@@ -165,11 +176,60 @@ patternProperties:
       - compatible
       - reg
       - interrupts
-      - st,adc-channels
-      - st,adc-channel-names
       - st,filter-order
       - "#io-channel-cells"
 
+    patternProperties:
+      "^channel@([0-7])$":
+        type: object
+        $ref: adc.yaml
+        unevaluatedProperties: false
+        description: Represents the external channels which are connected to the DFSDM.
+
+        properties:
+          reg:
+            maxItems: 1
+
+          label:
+            description:
+              Unique name to identify which channel this is.
+
+          st,adc-channel-type:
+            description: |
+              Single-ended channel input type.
+              - "SPI_R": SPI with data on rising edge (default)
+              - "SPI_F": SPI with data on falling edge
+              - "MANCH_R": manchester codec, rising edge = logic 0, falling edge = logic 1
+              - "MANCH_F": manchester codec, rising edge = logic 1, falling edge = logic 0
+            $ref: /schemas/types.yaml#/definitions/string
+            enum: [ SPI_R, SPI_F, MANCH_R, MANCH_F ]
+
+          st,adc-channel-clk-src:
+            description: |
+              Conversion clock source.
+              - "CLKIN": external SPI clock (CLKIN x)
+              - "CLKOUT": internal SPI clock (CLKOUT) (default)
+              - "CLKOUT_F": internal SPI clock divided by 2 (falling edge).
+              - "CLKOUT_R": internal SPI clock divided by 2 (rising edge).
+            $ref: /schemas/types.yaml#/definitions/string
+            enum: [ CLKIN, CLKOUT, CLKOUT_F, CLKOUT_R ]
+
+          st,adc-alt-channel:
+            description:
+              Must be defined if two sigma delta modulators are
+              connected on same SPI input.
+              If not set, channel n is connected to SPI input n.
+              If set, channel n is connected to SPI input n + 1.
+            type: boolean
+
+          io-backends:
+            description:
+              Used to pipe external sigma delta modulator or internal ADC backend to DFSDM channel.
+            maxItems: 1
+
+        required:
+          - reg
+
     allOf:
       - if:
           properties:
@@ -199,9 +259,19 @@ patternProperties:
               description:
                 From common IIO binding. Used to pipe external sigma delta
                 modulator or internal ADC output to DFSDM channel.
+              deprecated: true
 
-          required:
-            - io-channels
+          if:
+            required:
+              - st,adc-channels
+          then:
+            required:
+              - io-channels
+
+          patternProperties:
+            "^channel@([0-9])$":
+              required:
+                - io-backends
 
       - if:
           properties:
@@ -298,7 +368,77 @@ examples:
       #address-cells = <1>;
       #size-cells = <0>;
 
+      // Example 1: Audio use case with generic binding
       dfsdm0: filter@0 {
+        compatible = "st,stm32-dfsdm-dmic";
+        reg = <0>;
+        interrupts = <GIC_SPI 110 IRQ_TYPE_LEVEL_HIGH>;
+        dmas = <&dmamux1 101 0x400 0x01>;
+        dma-names = "rx";
+        #io-channel-cells = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        st,filter-order = <5>;
+
+        channel@1 {
+          reg = <1>;
+          label = "dmic0";
+          st,adc-channel-type = "SPI_R";
+          st,adc-channel-clk-src = "CLKOUT";
+          st,adc-alt-channel;
+        };
+
+        asoc_pdm0: dfsdm-dai {
+          compatible = "st,stm32h7-dfsdm-dai";
+          #sound-dai-cells = <0>;
+          io-channels = <&dfsdm0 0>;
+        };
+      };
+
+      // Example 1: Analog use case with generic binding
+      dfsdm1: filter@1 {
+        compatible = "st,stm32-dfsdm-adc";
+        reg = <1>;
+        interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
+        dmas = <&dmamux1 102 0x400 0x01>;
+        dma-names = "rx";
+        st,filter-order = <1>;
+        #io-channel-cells = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        channel@2 {
+          reg = <2>;
+          label = "in2";
+          st,adc-channel-type = "SPI_F";
+          st,adc-channel-clk-src = "CLKOUT";
+          st,adc-alt-channel;
+          io-backends = <&sd_adc2>;
+        };
+
+        channel@3 {
+          reg = <3>;
+          label = "in3";
+          st,adc-channel-type = "SPI_R";
+          st,adc-channel-clk-src = "CLKOUT";
+          io-backends = <&sd_adc3>;
+        };
+      };
+    };
+
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/stm32mp1-clks.h>
+    dfsdm_2: dfsdm@4400d000 {
+      compatible = "st,stm32mp1-dfsdm";
+      reg = <0x4400d000 0x800>;
+      clocks = <&rcc DFSDM_K>, <&rcc ADFSDM_K>;
+      clock-names = "dfsdm", "audio";
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      // Example 3: Audio use case with legacy binding
+      dfsdm0_2: filter@0 {
         compatible = "st,stm32-dfsdm-dmic";
         reg = <0>;
         interrupts = <GIC_SPI 110 IRQ_TYPE_LEVEL_HIGH>;
@@ -311,14 +451,15 @@ examples:
         st,adc-channel-clk-src = "CLKOUT";
         st,filter-order = <5>;
 
-        asoc_pdm0: dfsdm-dai {
+        asoc_pdm0_2: dfsdm-dai {
           compatible = "st,stm32h7-dfsdm-dai";
           #sound-dai-cells = <0>;
           io-channels = <&dfsdm0 0>;
         };
       };
 
-      dfsdm_pdm1: filter@1 {
+      // Example 3: Analog use case with legacy binding
+      dfsdm1_2: filter@1 {
         compatible = "st,stm32-dfsdm-adc";
         reg = <1>;
         interrupts = <GIC_SPI 111 IRQ_TYPE_LEVEL_HIGH>;
-- 
2.25.1

[PATCH v3 5/8] dt-bindings: iio: add backend support to sd modulator

[Olivier Moysan]

The legacy sd modulator driver registers the sigma delta modulator as
an IIO channel provider. This implementation is not convenient when the
SD modulator has to be cascaded with another IIO device. The scaling
information is distributed across devices, which makes it difficult to
report consistent scaling data on IIO devices.

The solution is to expose these cascaded IIO devices as an aggregate
device, which report global scaling information.
Add IIO backend support to SD modulator to allow scaling information
management.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 .../iio/adc/sigma-delta-modulator.yaml        | 24 +++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml b/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
index cab0d425eaa4..e34aa560da63 100644
--- a/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
@@ -18,18 +18,38 @@ properties:
       - sd-modulator
       - ads1201
 
+  '#io-backend-cells':
+    const: 0
+
   '#io-channel-cells':
     const: 0
 
+  reg:
+    maxItems: 1
+
+  vref-supply:
+    description: Phandle to the vref input analog reference voltage.
+
 required:
   - compatible
-  - '#io-channel-cells'
+
+allOf:
+  - anyOf:
+    - required: ['#io-backend-cells']
+    - required: ['#io-channel-cells']
 
 additionalProperties: false
 
 examples:
   - |
-    ads1202: adc {
+    // Exemple1: SD modulator is an IIO backend device
+    ads1201_0 {
+      compatible = "ti,ads1201";
+      #io-backend-cells = <0>;
+    };
+
+    //Example2: SD modulator is an IIO channel provider
+    ads1201_1 {
       compatible = "sd-modulator";
       #io-channel-cells = <0>;
     };
-- 
2.25.1

[PATCH v3 6/8] iio: adc: stm32-dfsdm: adopt generic channels bindings

[Olivier Moysan]

Move to generic channels binding to ease new backend framework adoption
and prepare the convergence with MDF IP support on STM32MP2 SoC family.

Legacy binding:
DFSDM is an IIO channel consumer.
SD modulator is an IIO channels provider.
The channel phandles are provided in DT through io-channels property
and channel indexes through st,adc-channels property.

New binding:
DFSDM is an IIO channel provider.
The channel indexes are given by reg property in channel child node.

This new binding is intended to be used with SD modulator IIO backends.
It does not support SD modulator legacy IIO devices.
The st,adc-channels property presence is used to discriminate
between legacy and backend bindings.

The support of the DFSDM legacy channels and SD modulator IIO devices
is kept for backward compatibility.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 drivers/iio/adc/stm32-dfsdm-adc.c | 200 ++++++++++++++++++++++++------
 1 file changed, 164 insertions(+), 36 deletions(-)

diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index fabd654245f5..ae5d95e38cd7 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
@@ -666,6 +666,64 @@ static int stm32_dfsdm_channel_parse_of(struct stm32_dfsdm *dfsdm,
 	return 0;
 }
 
+static int stm32_dfsdm_generic_channel_parse_of(struct stm32_dfsdm *dfsdm,
+						struct iio_dev *indio_dev,
+						struct iio_chan_spec *ch,
+						struct fwnode_handle *node)
+{
+	struct stm32_dfsdm_channel *df_ch;
+	const char *of_str;
+	int ret, val;
+
+	ret = fwnode_property_read_u32(node, "reg", &ch->channel);
+	if (ret < 0) {
+		dev_err(&indio_dev->dev, "Missing channel index %d\n", ret);
+		return ret;
+	}
+
+	if (ch->channel >= dfsdm->num_chs) {
+		dev_err(&indio_dev->dev, " Error bad channel number %d (max = %d)\n",
+			ch->channel, dfsdm->num_chs);
+		return -EINVAL;
+	}
+
+	ret = fwnode_property_read_string(node, "label", &ch->datasheet_name);
+	if (ret < 0) {
+		dev_err(&indio_dev->dev,
+			" Error parsing 'label' for idx %d\n", ch->channel);
+		return ret;
+	}
+
+	df_ch =  &dfsdm->ch_list[ch->channel];
+	df_ch->id = ch->channel;
+
+	ret = fwnode_property_read_string(node, "st,adc-channel-type", &of_str);
+	if (!ret) {
+		val = stm32_dfsdm_str2val(of_str, stm32_dfsdm_chan_type);
+		if (val < 0)
+			return val;
+	} else {
+		val = 0;
+	}
+	df_ch->type = val;
+
+	ret = fwnode_property_read_string(node, "st,adc-channel-clk-src", &of_str);
+	if (!ret) {
+		val = stm32_dfsdm_str2val(of_str, stm32_dfsdm_chan_src);
+		if (val < 0)
+			return val;
+	} else {
+		val = 0;
+	}
+	df_ch->src = val;
+
+	ret = fwnode_property_read_u32(node, "st,adc-alt-channel", &df_ch->alt_si);
+	if (ret != -EINVAL)
+		df_ch->alt_si = 0;
+
+	return 0;
+}
+
 static ssize_t dfsdm_adc_audio_get_spiclk(struct iio_dev *indio_dev,
 					  uintptr_t priv,
 					  const struct iio_chan_spec *chan,
@@ -1227,7 +1285,8 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 		ret = iio_device_claim_direct_mode(indio_dev);
 		if (ret)
 			return ret;
-		ret = iio_hw_consumer_enable(adc->hwc);
+		if (adc->hwc)
+			ret = iio_hw_consumer_enable(adc->hwc);
 		if (ret < 0) {
 			dev_err(&indio_dev->dev,
 				"%s: IIO enable failed (channel %d)\n",
@@ -1236,7 +1295,8 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 			return ret;
 		}
 		ret = stm32_dfsdm_single_conv(indio_dev, chan, val);
-		iio_hw_consumer_disable(adc->hwc);
+		if (adc->hwc)
+			iio_hw_consumer_disable(adc->hwc);
 		if (ret < 0) {
 			dev_err(&indio_dev->dev,
 				"%s: Conversion failed (channel %d)\n",
@@ -1362,15 +1422,20 @@ static int stm32_dfsdm_dma_request(struct device *dev,
 	return 0;
 }
 
-static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev,
-					 struct iio_chan_spec *ch)
+static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev, struct iio_chan_spec *ch,
+					 struct fwnode_handle *child)
 {
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
 	int ret;
 
-	ret = stm32_dfsdm_channel_parse_of(adc->dfsdm, indio_dev, ch);
-	if (ret < 0)
-		return ret;
+	if (child)
+		ret = stm32_dfsdm_generic_channel_parse_of(adc->dfsdm, indio_dev, ch, child);
+	else /* Legacy binding */
+		ret = stm32_dfsdm_channel_parse_of(adc->dfsdm, indio_dev, ch);
+	if (ret < 0) {
+		dev_err(&indio_dev->dev, "Failed to parse channel\n");
+		return dev_err_probe(&indio_dev->dev, ret, "Failed to parse channel\n");
+	}
 
 	ch->type = IIO_VOLTAGE;
 	ch->indexed = 1;
@@ -1385,6 +1450,7 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev,
 
 	if (adc->dev_data->type == DFSDM_AUDIO) {
 		ch->ext_info = dfsdm_adc_audio_ext_info;
+		ch->scan_index = 0;
 	} else {
 		ch->scan_type.shift = 8;
 	}
@@ -1396,20 +1462,67 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev,
 					  &adc->dfsdm->ch_list[ch->channel]);
 }
 
+static int stm32_dfsdm_chan_init(struct iio_dev *indio_dev, struct iio_chan_spec *channels)
+{
+	int num_ch = indio_dev->num_channels;
+	int chan_idx = 0;
+	int ret;
+
+	for (chan_idx = 0; chan_idx < num_ch; chan_idx++) {
+		channels[chan_idx].scan_index = chan_idx;
+		ret = stm32_dfsdm_adc_chan_init_one(indio_dev, &channels[chan_idx], NULL);
+		if (ret < 0)
+			return dev_err_probe(&indio_dev->dev, ret, "Channels init failed\n");
+	}
+
+	return 0;
+}
+
+static int stm32_dfsdm_generic_chan_init(struct iio_dev *indio_dev, struct iio_chan_spec *channels)
+{
+	int chan_idx = 0, ret;
+
+	device_for_each_child_node_scoped(&indio_dev->dev, child) {
+		/* Skip DAI node in DFSDM audio nodes */
+		if (fwnode_property_present(child, "compatible"))
+			continue;
+
+		channels[chan_idx].scan_index = chan_idx;
+		ret = stm32_dfsdm_adc_chan_init_one(indio_dev, &channels[chan_idx], child);
+		if (ret < 0)
+			return dev_err_probe(&indio_dev->dev, ret, "Channels init failed\n");
+
+		chan_idx++;
+	}
+
+	return chan_idx;
+}
+
 static int stm32_dfsdm_audio_init(struct device *dev, struct iio_dev *indio_dev)
 {
 	struct iio_chan_spec *ch;
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
 	struct stm32_dfsdm_channel *d_ch;
-	int ret;
+	bool legacy = false;
+	int num_ch, ret;
+
+	/* If st,adc-channels is defined legacy binding is used. Else assume generic binding. */
+	num_ch = of_property_count_u32_elems(indio_dev->dev.of_node, "st,adc-channels");
+	if (num_ch == 1)
+		legacy = true;
 
 	ch = devm_kzalloc(&indio_dev->dev, sizeof(*ch), GFP_KERNEL);
 	if (!ch)
 		return -ENOMEM;
 
-	ch->scan_index = 0;
+	indio_dev->num_channels = 1;
+	indio_dev->channels = ch;
+
+	if (legacy)
+		ret = stm32_dfsdm_chan_init(indio_dev, ch);
+	else
+		ret = stm32_dfsdm_generic_chan_init(indio_dev, ch);
 
-	ret = stm32_dfsdm_adc_chan_init_one(indio_dev, ch);
 	if (ret < 0) {
 		dev_err(&indio_dev->dev, "Channels init failed\n");
 		return ret;
@@ -1420,9 +1533,6 @@ static int stm32_dfsdm_audio_init(struct device *dev, struct iio_dev *indio_dev)
 	if (d_ch->src != DFSDM_CHANNEL_SPI_CLOCK_EXTERNAL)
 		adc->spi_freq = adc->dfsdm->spi_master_freq;
 
-	indio_dev->num_channels = 1;
-	indio_dev->channels = ch;
-
 	return stm32_dfsdm_dma_request(dev, indio_dev);
 }
 
@@ -1430,43 +1540,61 @@ static int stm32_dfsdm_adc_init(struct device *dev, struct iio_dev *indio_dev)
 {
 	struct iio_chan_spec *ch;
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
-	int num_ch;
-	int ret, chan_idx;
+	int num_ch, ret;
+	bool legacy = false;
 
 	adc->oversamp = DFSDM_DEFAULT_OVERSAMPLING;
 	ret = stm32_dfsdm_compute_all_osrs(indio_dev, adc->oversamp);
 	if (ret < 0)
 		return ret;
 
-	num_ch = of_property_count_u32_elems(indio_dev->dev.of_node,
-					     "st,adc-channels");
-	if (num_ch < 0 || num_ch > adc->dfsdm->num_chs) {
-		dev_err(&indio_dev->dev, "Bad st,adc-channels\n");
-		return num_ch < 0 ? num_ch : -EINVAL;
+	num_ch = device_get_child_node_count(&indio_dev->dev);
+	if (!num_ch) {
+		/* No channels nodes found. Assume legacy binding */
+		num_ch = of_property_count_u32_elems(indio_dev->dev.of_node, "st,adc-channels");
+		if (num_ch < 0) {
+			dev_err(&indio_dev->dev, "Bad st,adc-channels\n");
+			return num_ch;
+		}
+
+		legacy = true;
 	}
 
-	/* Bind to SD modulator IIO device */
-	adc->hwc = devm_iio_hw_consumer_alloc(&indio_dev->dev);
-	if (IS_ERR(adc->hwc))
-		return -EPROBE_DEFER;
+	if (num_ch > adc->dfsdm->num_chs) {
+		dev_err(&indio_dev->dev, "Number of channel [%d] exceeds [%d]\n",
+			num_ch, adc->dfsdm->num_chs);
+		return -EINVAL;
+	}
+	indio_dev->num_channels = num_ch;
 
-	ch = devm_kcalloc(&indio_dev->dev, num_ch, sizeof(*ch),
-			  GFP_KERNEL);
-	if (!ch)
-		return -ENOMEM;
+	if (legacy) {
+		/* Bind to SD modulator IIO device. */
+		adc->hwc = devm_iio_hw_consumer_alloc(&indio_dev->dev);
+		if (IS_ERR(adc->hwc))
+			return dev_err_probe(&indio_dev->dev, -EPROBE_DEFER,
+					     "waiting for SD modulator\n");
+	} else {
+		/* Generic binding. SD modulator IIO device not used. Use SD modulator backend. */
+		adc->hwc = NULL;
 
-	for (chan_idx = 0; chan_idx < num_ch; chan_idx++) {
-		ch[chan_idx].scan_index = chan_idx;
-		ret = stm32_dfsdm_adc_chan_init_one(indio_dev, &ch[chan_idx]);
-		if (ret < 0) {
-			dev_err(&indio_dev->dev, "Channels init failed\n");
-			return ret;
-		}
+		adc->backend = devm_kzalloc(&indio_dev->dev, sizeof(*adc->backend) * num_ch,
+					    GFP_KERNEL);
+		if (!adc->backend)
+			return -ENOMEM;
 	}
 
-	indio_dev->num_channels = num_ch;
+	ch = devm_kcalloc(&indio_dev->dev, num_ch, sizeof(*ch), GFP_KERNEL);
+	if (!ch)
+		return -ENOMEM;
 	indio_dev->channels = ch;
 
+	if (legacy)
+		ret = stm32_dfsdm_chan_init(indio_dev, ch);
+	else
+		ret = stm32_dfsdm_generic_chan_init(indio_dev, ch);
+	if (ret < 0)
+		return ret;
+
 	init_completion(&adc->completion);
 
 	/* Optionally request DMA */
-- 
2.25.1

[PATCH v3 7/8] iio: add iio backend support to sd modulator

[Olivier Moysan]

The legacy sd modulator driver registers the sigma delta modulator as
an IIO channel provider. This implementation is not convenient when the
SD modulator has to be cascaded with another IIO device. The scaling
information is distributed across devices, which makes it difficult to
report consistent scaling data on IIO devices.

The solution is to expose these cascaded IIO devices as an aggregate
device, which report global scaling information.
Add IIO backend support to SD modulator to allow scaling information
management.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
---
 drivers/iio/adc/Kconfig            |  1 +
 drivers/iio/adc/sd_adc_modulator.c | 92 +++++++++++++++++++++++++++++-
 2 files changed, 92 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index f60fe85a30d5..14b1773f02d9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1171,6 +1171,7 @@ config SD_ADC_MODULATOR
 	tristate "Generic sigma delta modulator"
 	select IIO_BUFFER
 	select IIO_TRIGGERED_BUFFER
+	select IIO_BACKEND
 	help
 	  Select this option to enables sigma delta modulator. This driver can
 	  support generic sigma delta modulators.
diff --git a/drivers/iio/adc/sd_adc_modulator.c b/drivers/iio/adc/sd_adc_modulator.c
index 327cc2097f6c..06f9c5cacd53 100644
--- a/drivers/iio/adc/sd_adc_modulator.c
+++ b/drivers/iio/adc/sd_adc_modulator.c
@@ -6,11 +6,14 @@
  * Author: Arnaud Pouliquen <arnaud.pouliquen@st.com>.
  */
 
+#include <linux/iio/backend.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/triggered_buffer.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
 
 static const struct iio_info iio_sd_mod_iio_info;
 
@@ -24,7 +27,54 @@ static const struct iio_chan_spec iio_sd_mod_ch = {
 	},
 };
 
-static int iio_sd_mod_probe(struct platform_device *pdev)
+struct iio_sd_backend_priv {
+	struct regulator *vref;
+	int vref_mv;
+};
+
+static int iio_sd_mod_enable(struct iio_backend *backend)
+{
+	struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);
+
+	if (priv->vref)
+		return regulator_enable(priv->vref);
+
+	return 0;
+};
+
+static void iio_sd_mod_disable(struct iio_backend *backend)
+{
+	struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);
+
+	if (priv->vref)
+		regulator_disable(priv->vref);
+};
+
+static int iio_sd_mod_read(struct iio_backend *backend, struct iio_chan_spec const *chan, int *val,
+			   int *val2, long mask)
+{
+	struct iio_sd_backend_priv *priv = iio_backend_get_priv(backend);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_SCALE:
+		*val = priv->vref_mv;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_OFFSET:
+		*val = 0;
+		return IIO_VAL_INT;
+	}
+
+	return -EOPNOTSUPP;
+};
+
+static const struct iio_backend_ops sd_backend_ops = {
+	.enable = iio_sd_mod_enable,
+	.disable = iio_sd_mod_disable,
+	.read_raw = iio_sd_mod_read,
+};
+
+static int iio_sd_mod_register(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct iio_dev *iio;
@@ -45,6 +95,45 @@ static int iio_sd_mod_probe(struct platform_device *pdev)
 	return devm_iio_device_register(&pdev->dev, iio);
 }
 
+static int iio_sd_mod_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct regulator *vref;
+	struct iio_sd_backend_priv *priv;
+	int ret;
+
+	/* If sd modulator is not defined as an IIO backend device, fallback to legacy */
+	if (!device_property_present(dev, "#io-backend-cells"))
+		return iio_sd_mod_register(pdev);
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	/*
+	 * Get regulator reference if any, but don't enable regulator right now.
+	 * Rely on enable and disable callbacks to manage regulator power.
+	 */
+	vref = devm_regulator_get_optional(dev, "vref");
+	if (IS_ERR(vref)) {
+		if (PTR_ERR(vref) != -ENODEV)
+			return dev_err_probe(dev, PTR_ERR(vref), "Failed to get vref\n");
+	} else {
+		/*
+		 * Retrieve voltage right now, as regulator_get_voltage() provides it whatever
+		 * the state of the regulator.
+		 */
+		ret = regulator_get_voltage(vref);
+		if (ret < 0)
+			return ret;
+
+		priv->vref = vref;
+		priv->vref_mv = ret / 1000;
+	}
+
+	return devm_iio_backend_register(&pdev->dev, &sd_backend_ops, priv);
+};
+
 static const struct of_device_id sd_adc_of_match[] = {
 	{ .compatible = "sd-modulator" },
 	{ .compatible = "ads1201" },
@@ -65,3 +154,4 @@ module_platform_driver(iio_sd_mod_adc);
 MODULE_DESCRIPTION("Basic sigma delta modulator");
 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
 MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS(IIO_BACKEND);
-- 
2.25.1

[PATCH v3 8/8] iio: adc: stm32-dfsdm: add scaling support to dfsdm

[Olivier Moysan]

Add scaling support to STM32 DFSDM.

When used in an analog context, a DFSDM filter typically converts the data
from a sigma delta modulator. The IIO device associated to the DFSDM
filter provides these data as raw data.
The IIO device can provide scaling information (voltage and offset) to
allow conversion of raw data into physical values.

With the new binding based on IIO backend framework, the sigma delta
modulators are defined as backends providing scaling information.

The scaling is not supported with legacy binding.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Acked-by: Nuno Sa <nuno.sa@analog.com>
---
 drivers/iio/adc/Kconfig           |  1 +
 drivers/iio/adc/stm32-dfsdm-adc.c | 98 ++++++++++++++++++++++++++++++-
 2 files changed, 97 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 14b1773f02d9..36ef0de9140f 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1226,6 +1226,7 @@ config STM32_DFSDM_ADC
 	select IIO_BUFFER
 	select IIO_BUFFER_HW_CONSUMER
 	select IIO_TRIGGERED_BUFFER
+	select IIO_BACKEND
 	help
 	  Select this option to support ADCSigma delta modulator for
 	  STMicroelectronics STM32 digital filter for sigma delta converter.
diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index ae5d95e38cd7..7e91e3df5592 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
@@ -9,6 +9,7 @@
 #include <linux/dmaengine.h>
 #include <linux/dma-mapping.h>
 #include <linux/iio/adc/stm32-dfsdm-adc.h>
+#include <linux/iio/backend.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/hw-consumer.h>
 #include <linux/iio/sysfs.h>
@@ -78,6 +79,7 @@ struct stm32_dfsdm_adc {
 	/* ADC specific */
 	unsigned int oversamp;
 	struct iio_hw_consumer *hwc;
+	struct iio_backend **backend;
 	struct completion completion;
 	u32 *buffer;
 
@@ -672,6 +674,8 @@ static int stm32_dfsdm_generic_channel_parse_of(struct stm32_dfsdm *dfsdm,
 						struct fwnode_handle *node)
 {
 	struct stm32_dfsdm_channel *df_ch;
+	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+	struct iio_backend *backend;
 	const char *of_str;
 	int ret, val;
 
@@ -721,6 +725,14 @@ static int stm32_dfsdm_generic_channel_parse_of(struct stm32_dfsdm *dfsdm,
 	if (ret != -EINVAL)
 		df_ch->alt_si = 0;
 
+	if (adc->dev_data->type == DFSDM_IIO) {
+		backend = devm_iio_backend_fwnode_get(&indio_dev->dev, NULL, node);
+		if (IS_ERR(backend))
+			return dev_err_probe(&indio_dev->dev, PTR_ERR(backend),
+					     "Failed to get backend\n");
+		adc->backend[ch->scan_index] = backend;
+	}
+
 	return 0;
 }
 
@@ -1056,6 +1068,7 @@ static int stm32_dfsdm_update_scan_mode(struct iio_dev *indio_dev,
 static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
 {
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+	int i = 0;
 	int ret;
 
 	/* Reset adc buffer index */
@@ -1067,6 +1080,15 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
 			return ret;
 	}
 
+	if (adc->backend) {
+		while (adc->backend[i]) {
+			ret = iio_backend_enable(adc->backend[i]);
+			if (ret < 0)
+				return ret;
+			i++;
+		}
+	}
+
 	ret = stm32_dfsdm_start_dfsdm(adc->dfsdm);
 	if (ret < 0)
 		goto err_stop_hwc;
@@ -1099,6 +1121,7 @@ static int stm32_dfsdm_postenable(struct iio_dev *indio_dev)
 static int stm32_dfsdm_predisable(struct iio_dev *indio_dev)
 {
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+	int i = 0;
 
 	stm32_dfsdm_stop_conv(indio_dev);
 
@@ -1106,6 +1129,13 @@ static int stm32_dfsdm_predisable(struct iio_dev *indio_dev)
 
 	stm32_dfsdm_stop_dfsdm(adc->dfsdm);
 
+	if (adc->backend) {
+		while (adc->backend[i]) {
+			iio_backend_disable(adc->backend[i]);
+			i++;
+		}
+	}
+
 	if (adc->hwc)
 		iio_hw_consumer_disable(adc->hwc);
 
@@ -1278,7 +1308,14 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 				int *val2, long mask)
 {
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
-	int ret;
+
+	struct stm32_dfsdm_filter *fl = &adc->dfsdm->fl_list[adc->fl_id];
+	struct stm32_dfsdm_filter_osr *flo = &fl->flo[fl->fast];
+	u32 max = flo->max << (flo->lshift - chan->scan_type.shift);
+	int ret, idx = chan->scan_index;
+
+	if (flo->lshift < chan->scan_type.shift)
+		max = flo->max >> (chan->scan_type.shift - flo->lshift);
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
@@ -1287,6 +1324,8 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 			return ret;
 		if (adc->hwc)
 			ret = iio_hw_consumer_enable(adc->hwc);
+		if (adc->backend)
+			ret = iio_backend_enable(adc->backend[idx]);
 		if (ret < 0) {
 			dev_err(&indio_dev->dev,
 				"%s: IIO enable failed (channel %d)\n",
@@ -1297,6 +1336,8 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 		ret = stm32_dfsdm_single_conv(indio_dev, chan, val);
 		if (adc->hwc)
 			iio_hw_consumer_disable(adc->hwc);
+		if (adc->backend)
+			iio_backend_disable(adc->backend[idx]);
 		if (ret < 0) {
 			dev_err(&indio_dev->dev,
 				"%s: Conversion failed (channel %d)\n",
@@ -1316,6 +1357,50 @@ static int stm32_dfsdm_read_raw(struct iio_dev *indio_dev,
 		*val = adc->sample_freq;
 
 		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		/*
+		 * Scale is expressed in mV.
+		 * When fast mode is disabled, actual resolution may be lower
+		 * than 2^n, where n = realbits - 1.
+		 * This leads to underestimating the input voltage.
+		 * To compensate this deviation, the voltage reference can be
+		 * corrected with a factor = realbits resolution / actual max
+		 */
+		if (adc->backend) {
+			ret = iio_backend_read_scale(adc->backend[idx], chan, val);
+			if (ret < 0)
+				return ret;
+
+			*val = div_u64((u64)*val * (u64)BIT(DFSDM_DATA_RES - 1), max);
+			*val2 = chan->scan_type.realbits;
+			if (chan->differential)
+				*val *= 2;
+		}
+		return IIO_VAL_FRACTIONAL_LOG2;
+
+	case IIO_CHAN_INFO_OFFSET:
+		/*
+		 * DFSDM output data are in the range [-2^n, 2^n],
+		 * with n = realbits - 1.
+		 * - Differential modulator:
+		 * Offset correspond to SD modulator offset.
+		 * - Single ended modulator:
+		 * Input is in [0V, Vref] range,
+		 * where 0V corresponds to -2^n, and Vref to 2^n.
+		 * Add 2^n to offset. (i.e. middle of input range)
+		 * offset = offset(sd) * vref / res(sd) * max / vref.
+		 */
+		if (adc->backend) {
+			ret = iio_backend_read_offset(adc->backend[idx], chan, val);
+			if (ret < 0)
+				return ret;
+
+			*val = div_u64((u64)max * *val, BIT(*val2 - 1));
+			if (!chan->differential)
+				*val += max;
+		}
+		return IIO_VAL_INT;
 	}
 
 	return -EINVAL;
@@ -1444,7 +1529,15 @@ static int stm32_dfsdm_adc_chan_init_one(struct iio_dev *indio_dev, struct iio_c
 	 * IIO_CHAN_INFO_RAW: used to compute regular conversion
 	 * IIO_CHAN_INFO_OVERSAMPLING_RATIO: used to set oversampling
 	 */
-	ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+	if (child) {
+		ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+					 BIT(IIO_CHAN_INFO_SCALE) |
+					 BIT(IIO_CHAN_INFO_OFFSET);
+	} else {
+		/* Legacy. Scaling not supported */
+		ch->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
+	}
+
 	ch->info_mask_shared_by_all = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
 					BIT(IIO_CHAN_INFO_SAMP_FREQ);
 
@@ -1805,3 +1898,4 @@ module_platform_driver(stm32_dfsdm_adc_driver);
 MODULE_DESCRIPTION("STM32 sigma delta ADC");
 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
 MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS(IIO_BACKEND);
-- 
2.25.1

Re: [PATCH v3 5/8] dt-bindings: iio: add backend support to sd modulator

[Rob Herring (Arm)]

On Wed, 03 Jul 2024 18:05:30 +0200, Olivier Moysan wrote:
> The legacy sd modulator driver registers the sigma delta modulator as
> an IIO channel provider. This implementation is not convenient when the
> SD modulator has to be cascaded with another IIO device. The scaling
> information is distributed across devices, which makes it difficult to
> report consistent scaling data on IIO devices.
> 
> The solution is to expose these cascaded IIO devices as an aggregate
> device, which report global scaling information.
> Add IIO backend support to SD modulator to allow scaling information
> management.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  .../iio/adc/sigma-delta-modulator.yaml        | 24 +++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 

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

yamllint warnings/errors:
./Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml:38:5: [warning] wrong indentation: expected 6 but found 4 (indentation)

dtschema/dtc warnings/errors:
Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.example.dtb: /example-0/ads1201_0: failed to match any schema with compatible: ['ti,ads1201']

doc reference errors (make refcheckdocs):

See https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20240703160535.2277871-6-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 v3 5/8] dt-bindings: iio: add backend support to sd modulator

[Rob Herring]

On Wed, Jul 03, 2024 at 06:05:30PM +0200, Olivier Moysan wrote:
> The legacy sd modulator driver registers the sigma delta modulator as
> an IIO channel provider. This implementation is not convenient when the
> SD modulator has to be cascaded with another IIO device. The scaling
> information is distributed across devices, which makes it difficult to
> report consistent scaling data on IIO devices.
> 
> The solution is to expose these cascaded IIO devices as an aggregate
> device, which report global scaling information.
> Add IIO backend support to SD modulator to allow scaling information
> management.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
> ---
>  .../iio/adc/sigma-delta-modulator.yaml        | 24 +++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml b/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
> index cab0d425eaa4..e34aa560da63 100644
> --- a/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
> @@ -18,18 +18,38 @@ properties:
>        - sd-modulator
>        - ads1201
>  
> +  '#io-backend-cells':
> +    const: 0
> +
>    '#io-channel-cells':
>      const: 0
>  
> +  reg:
> +    maxItems: 1
> +
> +  vref-supply:
> +    description: Phandle to the vref input analog reference voltage.
> +
>  required:
>    - compatible
> -  - '#io-channel-cells'
> +
> +allOf:

Don't need allOf

> +  - anyOf:
> +    - required: ['#io-backend-cells']
> +    - required: ['#io-channel-cells']
>  
>  additionalProperties: false
>  
>  examples:
>    - |
> -    ads1202: adc {
> +    // Exemple1: SD modulator is an IIO backend device
> +    ads1201_0 {
> +      compatible = "ti,ads1201";
> +      #io-backend-cells = <0>;
> +    };
> +
> +    //Example2: SD modulator is an IIO channel provider
> +    ads1201_1 {
>        compatible = "sd-modulator";
>        #io-channel-cells = <0>;

Don't you need some link between the nodes?

>      };
> -- 
> 2.25.1
>