[PATCH v8 01/12] dt-bindings: iio: adc: Add AD4170-4

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

Add device tree documentation for AD4170-4 and similar sigma-delta ADCs.
The AD4170-4 is a 24-bit, multichannel, sigma-delta ADC.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v7 -> v8
- Updated device name in patch description (AD4170 -> AD4170-4).
- Removed extra blank line at the end of the doc.

 .../bindings/iio/adc/adi,ad4170-4.yaml        | 554 ++++++++++++++++++
 MAINTAINERS                                   |   7 +
 2 files changed, 561 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4170-4.yaml

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4170-4.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4170-4.yaml
new file mode 100644
index 000000000000..da93213d12d4
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4170-4.yaml
@@ -0,0 +1,554 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ad4170-4.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD4170-4 and similar Analog to Digital Converters
+
+maintainers:
+  - Marcelo Schmitt <marcelo.schmitt@analog.com>
+
+description: |
+  Analog Devices AD4170-4 series of Sigma-delta Analog to Digital Converters.
+  Specifications can be found at:
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4170-4.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4190-4.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4195-4.pdf
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+$defs:
+  reference-buffer:
+    description: |
+      Enable precharge buffer, full buffer, or skip reference buffering of
+      the positive/negative voltage reference. Because the output impedance
+      of the source driving the voltage reference inputs may be dynamic,
+      resistive/capacitive combinations of those inputs can cause DC gain
+      errors if the reference inputs go unbuffered into the ADC. Enable
+      reference buffering if the provided reference source has dynamic high
+      impedance output. Note the absolute voltage allowed on REFINn+ and REFINn-
+      inputs is from AVSS - 50 mV to AVDD + 50 mV when the reference buffers are
+      disabled but narrows to AVSS to AVDD when reference buffering is enabled
+      or in precharge mode.
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ precharge, full, disabled ]
+    default: full
+
+properties:
+  compatible:
+    enum:
+      - adi,ad4170-4
+      - adi,ad4190-4
+      - adi,ad4195-4
+
+  avss-supply:
+    description:
+      Reference voltage supply for AVSS. A −2.625V minimum and 0V maximum supply
+      that powers the chip. If not provided, AVSS is assumed to be at system
+      ground (0V).
+
+  avdd-supply:
+    description:
+      A supply of 4.75V to 5.25V relative to AVSS that powers the chip (AVDD).
+
+  iovdd-supply:
+    description: 1.7V to 5.25V reference supply to the serial interface (IOVDD).
+
+  refin1p-supply:
+    description: REFIN+ supply that can be used as reference for conversion.
+
+  refin1n-supply:
+    description: REFIN- supply that can be used as reference for conversion.
+
+  refin2p-supply:
+    description: REFIN2+ supply that can be used as reference for conversion.
+
+  refin2n-supply:
+    description: REFIN2- supply that can be used as reference for conversion.
+
+  spi-cpol: true
+
+  spi-cpha: true
+
+  interrupts:
+    description:
+      Interrupt for signaling the completion of conversion results. The data
+      ready signal (RDY) used as interrupt is by default provided on the SDO
+      pin. Alternatively, it can be provided on the DIG_AUX1 pin in which case
+      the chip disables the RDY function on SDO. Thus, there can be only one
+      data ready interrupt enabled at a time.
+
+  interrupt-names:
+    description:
+      Specify which pin should be configured as Data Ready interrupt.
+    enum:
+      - sdo
+      - dig_aux1
+
+  clocks:
+    maxItems: 1
+    description:
+      Optional external clock source. Can specify either an external clock or
+      external crystal.
+
+  clock-names:
+    enum:
+      - ext-clk
+      - xtal
+    default: ext-clk
+
+  '#clock-cells':
+    const: 0
+
+  clock-output-names:
+    maxItems: 1
+
+  gpio-controller: true
+
+  "#gpio-cells":
+    const: 2
+    description: |
+      The first cell is for the GPIO number: 0 to 3.
+      The second cell takes standard GPIO flags.
+
+  ldac-gpios:
+    description:
+      GPIO connected to DIG_AUX2 pin to be used as LDAC toggle to control the
+      transfer of data from the DAC_INPUT_A register to the DAC.
+    maxItems: 1
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  adi,vbias-pins:
+    description: Analog inputs to apply a voltage bias of (AVDD − AVSS) / 2 to.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    minItems: 1
+    maxItems: 9
+    items:
+      minimum: 0
+      maximum: 8
+
+allOf:
+  # Some devices don't have integrated DAC
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - adi,ad4190-4
+              - adi,ad4195-4
+    then:
+      properties:
+        ldac-gpios: false
+
+  # Require to specify the interrupt pin when using interrupts
+  - if:
+      required:
+        - interrupts
+    then:
+      required:
+        - interrupt-names
+
+  # If an external clock is set, the internal clock cannot go out and vice versa
+  - oneOf:
+      - required: [clocks]
+        properties:
+          '#clock-cells': false
+      - required: ['#clock-cells']
+        properties:
+          clocks: false
+
+required:
+  - compatible
+  - reg
+  - avdd-supply
+  - iovdd-supply
+  - spi-cpol
+  - spi-cpha
+
+unevaluatedProperties: false
+
+patternProperties:
+  "^channel@[0-9a-f]$":
+    $ref: /schemas/iio/adc/adc.yaml#
+    unevaluatedProperties: false
+    description:
+      Represents the external channels which are connected to the ADC.
+
+    properties:
+      reg:
+        description:
+          The channel number.
+        minimum: 0
+        maximum: 15
+
+      diff-channels:
+        description: |
+          This property is used for defining the inputs of a differential
+          voltage channel. The first value is the positive input and the second
+          value is the negative input of the channel.
+
+          Besides the analog input pins AIN0 to AIN8, there are special inputs
+          that can be selected with the following values:
+          17: Internal temperature sensor
+          18: (AVDD-AVSS)/5
+          19: (IOVDD-DGND)/5
+          20: DAC output
+          21: ALDO
+          22: DLDO
+          23: AVSS
+          24: DGND
+          25: REFIN+
+          26: REFIN-
+          27: REFIN2+
+          28: REFIN2-
+          29: REFOUT
+          For the internal temperature sensor, use the input number for both
+          inputs (i.e. diff-channels = <17 17>).
+        items:
+          enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+                 26, 27, 28, 29]
+
+      adi,reference-select:
+        description: |
+          Select the reference source to use when converting on the
+          specific channel. Valid values are:
+          0: REFIN+/REFIN-
+          1: REFIN2+/REFIN2−
+          2: REFOUT/AVSS (internal reference)
+          3: AVDD/AVSS
+          If not specified, REFOUT/AVSS is used.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1, 2, 3]
+        default: 1
+
+      adi,positive-reference-buffer:
+        $ref: '#/$defs/reference-buffer'
+
+      adi,negative-reference-buffer:
+        $ref: '#/$defs/reference-buffer'
+
+      adi,sensor-type:
+        description:
+          The AD4170-4 and similar designs have features to aid interfacing with
+          load cell weigh scale, RTD, and thermocouple sensors. Each of those
+          sensor types requires either distinct wiring configuration or
+          external circuitry for proper sensor operation and can use different
+          ADC chip functionality on their setups. A key characteristic of those
+          external sensors is that they must be excited either by voltage supply
+          or by ADC chip excitation signals. The sensor can then be read through
+          a pair of analog inputs. This property specifies which particular
+          sensor type is connected to the ADC so it can be properly setup and
+          handled. Omit this property for conventional (not weigh scale, RTD, or
+          thermocouple) ADC channel setups.
+        $ref: /schemas/types.yaml#/definitions/string
+        enum: [ weighscale, rtd, thermocouple ]
+
+      adi,excitation-pin-0:
+        description:
+          Analog input to apply excitation current to while the channel
+          is active.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 20
+        default: 0
+
+      adi,excitation-pin-1:
+        description:
+          Analog input to apply excitation current to while the channel
+          is active.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 20
+        default: 0
+
+      adi,excitation-pin-2:
+        description:
+          Analog input to apply excitation current to while the channel
+          is active.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 20
+        default: 0
+
+      adi,excitation-pin-3:
+        description:
+          Analog input to apply excitation current to while the channel
+          is active.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 20
+        default: 0
+
+      adi,excitation-current-0-microamp:
+        description:
+          Excitation current in microamperes to be applied to pin specified in
+          adi,excitation-pin-0 while this channel is active.
+        enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+        default: 0
+
+      adi,excitation-current-1-microamp:
+        description:
+          Excitation current in microamperes to be applied to pin specified in
+          adi,excitation-pin-1 while this channel is active.
+        enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+        default: 0
+
+      adi,excitation-current-2-microamp:
+        description:
+          Excitation current in microamperes to be applied to pin specified in
+          adi,excitation-pin-2 while this channel is active.
+        enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+        default: 0
+
+      adi,excitation-current-3-microamp:
+        description:
+          Excitation current in microamperes to be applied to pin specified in
+          adi,excitation-pin-3 while this channel is active.
+        enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+        default: 0
+
+      adi,excitation-ac:
+        type: boolean
+        description:
+          Whether the external sensor has to be AC or DC excited. When omitted,
+          it is DC excited.
+
+    allOf:
+      - oneOf:
+          - required: [single-channel, common-mode-channel]
+            properties:
+              diff-channels: false
+          - required: [diff-channels]
+            properties:
+              single-channel: false
+              common-mode-channel: false
+      # Usual ADC channels don't need external circuitry excitation.
+      - if:
+          not:
+            required:
+              - adi,sensor-type
+        then:
+          properties:
+            adi,excitation-pin-0: false
+            adi,excitation-pin-1: false
+            adi,excitation-pin-2: false
+            adi,excitation-pin-3: false
+            adi,excitation-current-0-microamp: false
+            adi,excitation-current-1-microamp: false
+            adi,excitation-current-2-microamp: false
+            adi,excitation-current-3-microamp: false
+            adi,excitation-ac: false
+      # Weigh scale bridge AC excited with one pair of predefined signals.
+      - if:
+          allOf:
+            - properties:
+                adi,sensor-type:
+                  contains:
+                    const: weighscale
+            - required:
+                - adi,excitation-ac
+                - adi,excitation-pin-2
+                - adi,excitation-pin-3
+            - not:
+                required:
+                  - adi,excitation-current-2-microamp
+                  - adi,excitation-current-3-microamp
+        then:
+          properties:
+            adi,excitation-pin-2:
+              const: 19
+            adi,excitation-pin-3:
+              const: 20
+      # Weigh scale bridge AC excited with two pairs of predefined signals.
+      - if:
+          allOf:
+            - properties:
+                adi,sensor-type:
+                  contains:
+                    const: weighscale
+            - required:
+                - adi,excitation-ac
+                - adi,excitation-pin-0
+                - adi,excitation-pin-1
+                - adi,excitation-pin-2
+                - adi,excitation-pin-3
+            - not:
+                required:
+                  - adi,excitation-current-0-microamp
+                  - adi,excitation-current-1-microamp
+                  - adi,excitation-current-2-microamp
+                  - adi,excitation-current-3-microamp
+        then:
+          properties:
+            adi,excitation-pin-0:
+              const: 17
+            adi,excitation-pin-1:
+              const: 18
+            adi,excitation-pin-2:
+              const: 19
+            adi,excitation-pin-3:
+              const: 20
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,ad4170-4";
+            reg = <0>;
+            spi-max-frequency = <20000000>;
+            spi-cpol;
+            spi-cpha;
+            avdd-supply = <&avdd>;
+            iovdd-supply = <&iovdd>;
+            clocks = <&clk>;
+            clock-names = "xtal";
+            interrupts = <0 IRQ_TYPE_EDGE_FALLING>;
+            interrupt-names = "dig_aux1";
+            adi,vbias-pins = <8>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            // Sample AIN0 with respect to DGND throughout AVDD/DGND input range
+            // Pseudo-differential unipolar
+            channel@0 {
+                reg = <0>;
+                single-channel = <0>;
+                common-mode-channel = <24>;
+                adi,reference-select = <3>;
+            };
+            // Weigh scale sensor
+            channel@1 {
+                reg = <1>;
+                bipolar;
+                diff-channels = <1 2>;
+                adi,reference-select = <0>;
+                adi,positive-reference-buffer = "precharge";
+                adi,negative-reference-buffer = "precharge";
+                adi,sensor-type = "weighscale";
+                adi,excitation-pin-2 = <19>;
+                adi,excitation-pin-3 = <20>;
+                adi,excitation-ac;
+            };
+            // RTD sensor
+            channel@2 {
+                reg = <2>;
+                bipolar;
+                diff-channels = <3 4>;
+                adi,reference-select = <0>;
+                adi,sensor-type = "rtd";
+                adi,excitation-pin-0 = <5>;
+                adi,excitation-pin-1 = <6>;
+                adi,excitation-current-0-microamp = <500>;
+                adi,excitation-current-1-microamp = <500>;
+                adi,excitation-ac;
+            };
+            // Thermocouple sensor
+            channel@3 {
+                reg = <3>;
+                bipolar;
+                diff-channels = <7 8>;
+                adi,reference-select = <0>;
+                adi,sensor-type = "thermocouple";
+                adi,excitation-pin-0 = <18>;
+                adi,excitation-current-0-microamp = <500>;
+            };
+        };
+    };
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "adi,ad4170-4";
+            reg = <0>;
+            spi-max-frequency = <20000000>;
+            spi-cpol;
+            spi-cpha;
+            avdd-supply = <&avdd>;
+            iovdd-supply = <&iovdd>;
+            #clock-cells = <0>;
+            clock-output-names = "ad4170-clk16mhz";
+            interrupts = <0 IRQ_TYPE_EDGE_FALLING>;
+            interrupt-names = "dig_aux1";
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            // Sample AIN0 with respect to AIN1 throughout AVDD/AVSS input range
+            // Differential bipolar. If AVSS < 0V, differential true bipolar
+            channel@0 {
+                reg = <0>;
+                bipolar;
+                diff-channels = <0 1>;
+                adi,reference-select = <3>;
+            };
+            // Sample AIN2 with respect to DGND throughout AVDD/DGND input range
+            // Pseudo-differential unipolar
+            channel@1 {
+                reg = <1>;
+                single-channel = <2>;
+                common-mode-channel = <24>;
+                adi,reference-select = <3>;
+            };
+            // Sample AIN3 with respect to 2.5V throughout AVDD/AVSS input range
+            // Pseudo-differential bipolar
+            channel@2 {
+                reg = <2>;
+                bipolar;
+                single-channel = <3>;
+                common-mode-channel = <29>;
+                adi,reference-select = <3>;
+            };
+            // Sample AIN4 with respect to DGND throughout AVDD/AVSS input range
+            // Pseudo-differential bipolar
+            channel@3 {
+                reg = <3>;
+                bipolar;
+                single-channel = <4>;
+                common-mode-channel = <24>;
+                adi,reference-select = <3>;
+            };
+            // Sample AIN5 with respect to 2.5V throughout AVDD/AVSS input range
+            // Pseudo-differential unipolar (AD4170-4 datasheet page 46 example)
+            channel@4 {
+                reg = <4>;
+                single-channel = <5>;
+                common-mode-channel = <29>;
+                adi,reference-select = <3>;
+            };
+            // Sample AIN6 with respect to 2.5V throughout REFIN+/REFIN- input range
+            // Pseudo-differential bipolar
+            channel@5 {
+                reg = <5>;
+                bipolar;
+                single-channel = <6>;
+                common-mode-channel = <29>;
+                adi,reference-select = <0>;
+            };
+            // Weigh scale sensor
+            channel@6 {
+                reg = <6>;
+                bipolar;
+                diff-channels = <7 8>;
+                adi,reference-select = <0>;
+                adi,sensor-type = "weighscale";
+                adi,excitation-pin-0 = <17>;
+                adi,excitation-pin-1 = <18>;
+                adi,excitation-pin-2 = <19>;
+                adi,excitation-pin-3 = <20>;
+                adi,excitation-ac;
+            };
+        };
+    };
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index d0809d62ff48..f50f555c160b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1392,6 +1392,13 @@ F:	Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad4130.yaml
 F:	drivers/iio/adc/ad4130.c
 
+ANALOG DEVICES INC AD4170-4 DRIVER
+M:	Marcelo Schmitt <marcelo.schmitt@analog.com>
+L:	linux-iio@vger.kernel.org
+S:	Supported
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/adi,ad4170-4.yaml
+
 ANALOG DEVICES INC AD4695 DRIVER
 M:	Michael Hennerich <michael.hennerich@analog.com>
 M:	Nuno Sá <nuno.sa@analog.com>
-- 
2.47.2