Re: [PATCH v3 2/2] dt-bindings: iio: Add ltc2983 documentation

[Rob Herring <robh+dt@kernel.org>]

On Fri, Oct 4, 2019 at 8:55 AM Nuno Sá <nuno.sa@analog.com> wrote:
>
> Document the LTC2983 temperature sensor devicetree bindings.
>
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> ---
> Changes in v2:
>  * Drop maxItems in non-array elements;
>  * Set adi,mux-delay-config-us instead of adi,mux-delay-config;
>  * Wrapped lines at 80 char;
>  * Added comas to enum elements;
>  * Use real units in adi,excitation-current;
>  * Moved some enums to minimum and maximum;
>  * Grouped patternProperties and moved reg property as a generic property.
>
> Changes in v3:
>  * Add meaning to adi,sensor-type values which are not const;
>  * Add meaning to adi,filter-notch-freq values;
>  * Break up adi,sensor-config into human readable elements;
>  * Set maxItems/minItems at the same identation as allOf in adi,custom-sensor;
>  * Fixed the maximum value for adi,sensor-type for sensors with custom support;
>  * Changed license to GPL-2.0-only as it should be for new bindings;
>  * Changed spi0 to spi in the dts example;
>  * Updated the dts example to the new properties.
>
>  .../bindings/iio/temperature/adi,ltc2983.yaml | 479 ++++++++++++++++++
>  MAINTAINERS                                   |   1 +
>  2 files changed, 480 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
>
> diff --git a/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
> new file mode 100644
> index 000000000000..b7101a0e84db
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml
> @@ -0,0 +1,479 @@
> +# SPDX-License-Identifier: GPL-2.0-only

(GPL-2.0-only OR BSD-2-Clause) for new bindings please.

> +%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,temperature-celcius:

-celsius. However, that suffix is reserved for properties whose value
is in Celsius, so you'll have to come up with something else.

How does one decide how to set this? Seems like the driver should just
decide based on what it needs to present to the user.

> +    description:
> +      If this property is present, the temperature is reported in Celsius.
> +    type: boolean
> +
> +  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.
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +      - maximum: 255

Standard unit suffixes already have a type, so just:

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

Drop the '-' on the last entry (making the min/max a single schema).

> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +patternProperties:
> +  ".*@([1-9]|1[0-9]|20)$":

'.*' can be dropped.

> +    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
> +
> +    required:
> +      - reg
> +
> +    patternProperties:
> +      "^thermocouple@.*":

You've made this node a child of '.*@([1-9]|1[0-9]|20)$'. This needs
to be at the same level.

> +        type: object
> +        description: |

You can drop the '|' where you don't need any formatting.

> +          Represents a thermocouple sensor which is connected to one of the device
> +          channels.
> +
> +        properties:
> +          adi,sensor-type:
> +            description: |
> +              Identifies the type of thermocouple connected to the device.
> +              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

You can move the type definition under ".*@([1-9]|1[0-9]|20)$" and
then just have the min/max here.

> +              - 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.
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint32
> +              - 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-sensor:
> +            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

We normally do things in microVolts. It seems strange to need 64-bits
of range for voltage and temperature.

> +              more details look at table 69 and 70.
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/int64-array

Fails on 'make dt_binding_check':

Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yaml:
Unresolvable JSON pointer: 'definitions/int64-array'

If this is pairs of values, it should really be defined as a matrix:

minItems: 3
maxItems: 64
items:
  minItems: 2
  maxItems: 2

Though I'll need to add uint64-matrix as a type (assuming this really
needs to be 64-bit).


> +            minItems: 6
> +            maxItems: 128
> +
> +        required:
> +          - adi,sensor-type
> +
> +      "^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.
> +            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).
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint32
> +              - 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.
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint32
> +
> +        required:
> +          - adi,sensor-type
> +
> +      "^rtd@.*":
> +        type: object
> +        description: |
> +          Represents a rtd sensor which is connected to one of the device channels.
> +
> +        properties:
> +          reg:
> +            minimum: 2
> +
> +          adi,sensor-type:
> +            description: |
> +              Identifies the type of RTD connected to the device.
> +              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.
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint32

You can drop the type here too.

> +              - 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-sensor:
> +            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.

It's not great to make one property name have different meanings.

> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint64-array
> +            minItems: 6
> +            maxItems: 128
> +
> +        required:
> +          - adi,sensor-type
> +          - 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: |
> +              Identifies the type of thermistor connected to the
> +              device.
> +              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-sensor:
> +            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. Steinhart-Hart coefficients are also supported and can
> +              be programmed into the device memory using this property. For
> +              Steinhart sensors, this table has a constant size of 6 entries
> +              (defining the coefficients) and the values are given in the raw
> +              format. Look at table 82 for more information.
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint64-array
> +            minItems: 6
> +            maxItems: 128
> +
> +        required:
> +          - adi,sensor-type
> +          - 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.
> +            const: 30
> +
> +          adi,single-ended:
> +            description: Boolean property which set's the adc as single-ended.
> +            type: boolean
> +
> +        required:
> +          - adi,sensor-type
> +
> +      "^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
> +
> +          adi,sensor-type:
> +            description: Identifies the sensor as a rsense.
> +            const: 29
> +
> +          adi,rsense-val-micro-ohms:
> +            description: |
> +              Sets the value of the sense resistor. Look at table 20 of the
> +              datasheet for information.
> +            allOf:
> +              - $ref: /schemas/types.yaml#/definitions/uint64

-micro-ohms is already defined to be 32-bit.

> +
> +        required:
> +          - adi,sensor-type
> +          - adi, rsense-val

spurious space.

> +
> +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>;
> +
> +                adi,temperature-celcius;
> +                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-micro-ohms = /bits/ 64 <1200000000>; //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-sensor = /bits/ 64 <0x00F371EC 0x12345678
> +                                        0x2C0F8733 0x10018C66 0xA0FEACCD
> +                                        0x90021D99>; //6 entries
> +                };
> +
> +                thermocouple@20 {
> +                        reg = <20>;
> +                        adi,sensor-type = <9>; //custom thermocouple
> +                        adi,single-ended;
> +                        adi,custom-sensor = /bits/ 64
> +                                 <(-50220000) 0
> +                                  (-30200000) 99100000
> +                                  (-5300000) 135400000
> +                                  0 273150000
> +                                  40200000 361200000
> +                                  55300000 522100000
> +                                  88300000 720300000
> +                                  132200000 811200000
> +                                  188700000 922500000
> +                                  460400000 1000000000>; //10 pairs
> +               };
> +
> +        };
> +    };
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 14a256e785ca..f747a9dc27f5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9497,6 +9497,7 @@ 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>
> --
> 2.23.0
>