dt-bindings: iio: Add ltc2983 documentation

Document the LTC2983 temperature sensor devicetree bindings.

Tweaked by Jonathan to take into account the lack of signed output
being maintained by dtc yaml output.  For now a comment added
that the unsigned array should actually be signed.
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/temperature/adi,ltc2983.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices LTC2983 Multi-sensor Temperature system
+
+maintainers:
+  - Nuno Sá <nuno.sa@analog.com>
+
+description: |
+  Analog Devices LTC2983 Multi-Sensor Digital Temperature Measurement System
+  https://www.analog.com/media/en/technical-documentation/data-sheets/2983fc.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,ltc2983
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  adi,mux-delay-config-us:
+    description:
+      The LTC2983 performs 2 or 3 internal conversion cycles per temperature
+      result. Each conversion cycle is performed with different excitation and
+      input multiplexer configurations. Prior to each conversion, these
+      excitation circuits and input switch configurations are changed and an
+      internal 1ms delay ensures settling prior to the conversion cycle in most
+      cases. An extra delay can be configured using this property. The value is
+      rounded to nearest 100us.
+    maximum: 255
+
+  adi,filter-notch-freq:
+    description:
+      Set's the default setting of the digital filter. The default is
+      simultaneous 50/60Hz rejection.
+      0 - 50/60Hz rejection
+      1 - 60Hz rejection
+      2 - 50Hz rejection
+    allOf:
+      - $ref: /schemas/types.yaml#/definitions/uint32
+      - minimum: 0
+        maximum: 2
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+patternProperties:
+  "@([1-9]|1[0-9]|20)$":
+    type: object
+
+    properties:
+      reg:
+        description:
+          The channel number. It can be connected to one of the 20 channels of
+          the device.
+        minimum: 1
+        maximum: 20
+
+      adi,sensor-type:
+        description: Identifies the type of sensor connected to the device.
+        $ref: /schemas/types.yaml#/definitions/uint32
+
+    required:
+      - reg
+      - adi,sensor-type
+
+  "^thermocouple@":
+    type: object
+    description:
+      Represents a thermocouple sensor which is connected to one of the device
+      channels.
+
+    properties:
+      adi,sensor-type:
+        description: |
+          1 - Type J Thermocouple
+          2 - Type K Thermocouple
+          3 - Type E Thermocouple
+          4 - Type N Thermocouple
+          5 - Type R Thermocouple
+          6 - Type S Thermocouple
+          7 - Type T Thermocouple
+          8 - Type B Thermocouple
+          9 - Custom Thermocouple
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 1
+        maximum: 9
+
+      adi,single-ended:
+        description:
+          Boolean property which set's the thermocouple as single-ended.
+        type: boolean
+
+      adi,sensor-oc-current-microamp:
+        description:
+          This property set's the pulsed current value applied during
+          open-circuit detect.
+        enum: [10, 100, 500, 1000]
+
+      adi,cold-junction-handle:
+        description:
+          Phandle which points to a sensor object responsible for measuring
+          the thermocouple cold junction temperature.
+        $ref: "/schemas/types.yaml#/definitions/phandle"
+
+      adi,custom-thermocouple:
+        description:
+          This is a table, where each entry should be a pair of
+          voltage(mv)-temperature(K). The entries must be given in nv and uK
+          so that, the original values must be multiplied by 1000000. For
+          more details look at table 69 and 70.
+          Note should be signed, but dtc doesn't currently maintain the
+          sign.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint64-matrix
+        items:
+          minItems: 3
+          maxItems: 64
+          items:
+            minItems: 2
+            maxItems: 2
+
+  "^diode@":
+    type: object
+    description:
+      Represents a diode sensor which is connected to one of the device
+      channels.
+
+    properties:
+      adi,sensor-type:
+        description: Identifies the sensor as a diode.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+        const: 28
+
+      adi,single-ended:
+        description: Boolean property which set's the diode as single-ended.
+        type: boolean
+
+      adi,three-conversion-cycles:
+        description:
+          Boolean property which set's three conversion cycles removing
+          parasitic resistance effects between the LTC2983 and the diode.
+        type: boolean
+
+      adi,average-on:
+        description:
+          Boolean property which enables a running average of the diode
+          temperature reading. This reduces the noise when the diode is used
+          as a cold junction temperature element on an isothermal block
+          where temperatures change slowly.
+        type: boolean
+
+      adi,excitation-current-microamp:
+        description:
+          This property controls the magnitude of the excitation current
+          applied to the diode. Depending on the number of conversions
+          cycles, this property will assume different predefined values on
+          each cycle. Just set the value of the first cycle (1l).
+        enum: [10, 20, 40, 80]
+
+      adi,ideal-factor-value:
+        description:
+          This property sets the diode ideality factor. The real value must
+          be multiplied by 1000000 to remove the fractional part. For more
+          information look at table 20 of the datasheet.
+        $ref: /schemas/types.yaml#/definitions/uint32
+
+  "^rtd@":
+    type: object
+    description:
+      Represents a rtd sensor which is connected to one of the device channels.
+
+    properties:
+      reg:
+        minimum: 2
+        maximum: 20
+
+      adi,sensor-type:
+        description: |
+          10 - RTD PT-10
+          11 - RTD PT-50
+          12 - RTD PT-100
+          13 - RTD PT-200
+          14 - RTD PT-500
+          15 - RTD PT-1000
+          16 - RTD PT-1000 (0.00375)
+          17 - RTD NI-120
+          18 - RTD Custom
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 10
+        maximum: 18
+
+      adi,rsense-handle:
+        description:
+          Phandle pointing to a rsense object associated with this RTD.
+        $ref: "/schemas/types.yaml#/definitions/phandle"
+
+      adi,number-of-wires:
+        description:
+          Identifies the number of wires used by the RTD. Setting this
+          property to 5 means 4 wires with Kelvin Rsense.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+          - enum: [2, 3, 4, 5]
+
+      adi,rsense-share:
+        description:
+          Boolean property which enables Rsense sharing, where one sense
+          resistor is used for multiple 2-, 3-, and/or 4-wire RTDs.
+        type: boolean
+
+      adi,current-rotate:
+        description:
+          Boolean property which enables excitation current rotation to
+          automatically remove parasitic thermocouple effects. Note that
+          this property is not allowed for 2- and 3-wire RTDs.
+        type: boolean
+
+      adi,excitation-current-microamp:
+        description:
+          This property controls the magnitude of the excitation current
+          applied to the RTD.
+        enum: [5, 10, 25, 50, 100, 250, 500, 1000]
+
+      adi,rtd-curve:
+        description:
+          This property set the RTD curve used and the corresponding
+          Callendar-VanDusen constants. Look at table 30 of the datasheet.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+          - minimum: 0
+            maximum: 3
+
+      adi,custom-rtd:
+        description:
+          This is a table, where each entry should be a pair of
+          resistance(ohm)-temperature(K). The entries added here are in uohm
+          and uK. For more details values look at table 74 and 75.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint64-matrix
+        items:
+          minItems: 3
+          maxItems: 64
+          items:
+            minItems: 2
+            maxItems: 2
+
+    required:
+      - adi,rsense-handle
+
+    dependencies:
+      adi,current-rotate: [ adi,rsense-share ]
+
+  "^thermistor@":
+    type: object
+    description:
+      Represents a thermistor sensor which is connected to one of the device
+      channels.
+
+    properties:
+      adi,sensor-type:
+        description:
+          19 - Thermistor 44004/44033 2.252kohm at 25°C
+          20 - Thermistor 44005/44030 3kohm at 25°C
+          21 - Thermistor 44007/44034 5kohm at 25°C
+          22 - Thermistor 44006/44031 10kohm at 25°C
+          23 - Thermistor 44008/44032 30kohm at 25°C
+          24 - Thermistor YSI 400 2.252kohm at 25°C
+          25 - Thermistor Spectrum 1003k 1kohm
+          26 - Thermistor Custom Steinhart-Hart
+          27 - Custom Thermistor
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 19
+        maximum: 27
+
+      adi,rsense-handle:
+        description:
+          Phandle pointing to a rsense object associated with this
+          thermistor.
+        $ref: "/schemas/types.yaml#/definitions/phandle"
+
+      adi,single-ended:
+        description:
+          Boolean property which set's the thermistor as single-ended.
+        type: boolean
+
+      adi,rsense-share:
+        description:
+          Boolean property which enables Rsense sharing, where one sense
+          resistor is used for multiple thermistors. Note that this property
+          is ignored if adi,single-ended is set.
+        type: boolean
+
+      adi,current-rotate:
+        description:
+          Boolean property which enables excitation current rotation to
+          automatically remove parasitic thermocouple effects.
+        type: boolean
+
+      adi,excitation-current-nanoamp:
+        description:
+          This property controls the magnitude of the excitation current
+          applied to the thermistor. Value 0 set's the sensor in auto-range
+          mode.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+          - enum: [0, 250, 500, 1000, 5000, 10000, 25000, 50000, 100000,
+                   250000, 500000, 1000000]
+
+      adi,custom-thermistor:
+        description:
+          This is a table, where each entry should be a pair of
+          resistance(ohm)-temperature(K). The entries added here are in uohm
+          and uK only for custom thermistors. For more details look at table
+          78 and 79.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint64-matrix
+        items:
+          minItems: 3
+          maxItems: 64
+          items:
+            minItems: 2
+            maxItems: 2
+
+      adi,custom-steinhart:
+        description:
+          Steinhart-Hart coefficients are also supported and can
+          be programmed into the device memory using this property. For
+          Steinhart sensors the coefficients are given in the raw
+          format. Look at table 82 for more information.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32-array
+        items:
+          minItems: 6
+          maxItems: 6
+
+    required:
+      - adi,rsense-handle
+
+    dependencies:
+      adi,current-rotate: [ adi,rsense-share ]
+
+  "^adc@":
+    type: object
+    description: Represents a channel which is being used as a direct adc.
+
+    properties:
+      adi,sensor-type:
+        description: Identifies the sensor as a direct adc.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+        const: 30
+
+      adi,single-ended:
+        description: Boolean property which set's the adc as single-ended.
+        type: boolean
+
+  "^rsense@":
+    type: object
+    description:
+      Represents a rsense which is connected to one of the device channels.
+      Rsense are used by thermistors and RTD's.
+
+    properties:
+      reg:
+        minimum: 2
+        maximum: 20
+
+      adi,sensor-type:
+        description: Identifies the sensor as a rsense.
+        allOf:
+          - $ref: /schemas/types.yaml#/definitions/uint32
+        const: 29
+
+      adi,rsense-val-milli-ohms:
+        description:
+          Sets the value of the sense resistor. Look at table 20 of the
+          datasheet for information.
+
+    required:
+      - adi,rsense-val-milli-ohms
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        sensor_ltc2983: ltc2983@0 {
+                compatible = "adi,ltc2983";
+                reg = <0>;
+
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                interrupts = <20 IRQ_TYPE_EDGE_RISING>;
+                interrupt-parent = <&gpio>;
+
+                thermocouple@18 {
+                        reg = <18>;
+                        adi,sensor-type = <8>; //Type B
+                        adi,sensor-oc-current-microamp = <10>;
+                        adi,cold-junction-handle = <&diode5>;
+                };
+
+                diode5: diode@5 {
+                        reg = <5>;
+                        adi,sensor-type = <28>;
+                };
+
+                rsense2: rsense@2 {
+                        reg = <2>;
+                        adi,sensor-type = <29>;
+                        adi,rsense-val-milli-ohms = <1200000>; //1.2Kohms
+                };
+
+                rtd@14 {
+                        reg = <14>;
+                        adi,sensor-type = <15>; //PT1000
+                        /*2-wire, internal gnd, no current rotation*/
+                        adi,number-of-wires = <2>;
+                        adi,rsense-share;
+                        adi,excitation-current-microamp = <500>;
+                        adi,rsense-handle = <&rsense2>;
+                };
+
+                adc@10 {
+                        reg = <10>;
+                        adi,sensor-type = <30>;
+                        adi,single-ended;
+                };
+
+                thermistor@12 {
+                        reg = <12>;
+                        adi,sensor-type = <26>; //Steinhart
+                        adi,rsense-handle = <&rsense2>;
+                        adi,custom-steinhart = <0x00F371EC 0x12345678
+                                        0x2C0F8733 0x10018C66 0xA0FEACCD
+                                        0x90021D99>; //6 entries
+                };
+
+                thermocouple@20 {
+                        reg = <20>;
+                        adi,sensor-type = <9>; //custom thermocouple
+                        adi,single-ended;
+                        adi,custom-thermocouple = /bits/ 64
+                                 <(-50220000) 0
+                                  (-30200000) 99100000
+                                  (-5300000) 135400000
+                                  0 273150000
+                                  40200000 361200000
+                                  55300000 522100000
+                                  88300000 720300000
+                                  132200000 811200000
+                                  188700000 922500000
+                                  460400000 1000000000>; //10 pairs
+               };
+
+        };
+    };
+...

MAINTAINERS

@@ -9629,6 +9629,7 @@ W:	http://ez.analog.com/community/linux-device-drivers
 L:	linux-iio@vger.kernel.org
 S:	Supported
 F:	drivers/iio/temperature/ltc2983.c
+F:	Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
 
 LTC4261 HARDWARE MONITOR DRIVER
 M:	Guenter Roeck <linux@roeck-us.net>