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

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

On Mon, Oct 7, 2019 at 11:17 AM Sa, Nuno <Nuno.Sa@analog.com> wrote:
>
> On Mon, 2019-10-07 at 09:45 -0500, Rob Herring wrote:
> > 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.yam
> > > l
> > > b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yam
> > > l
> > > new file mode 100644
> > > index 000000000000..b7101a0e84db
> > > --- /dev/null
> > > +++
> > > b/Documentation/devicetree/bindings/iio/temperature/adi,ltc2983.yam
> > > l
> > > @@ -0,0 +1,479 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only
> >
> > (GPL-2.0-only OR BSD-2-Clause) for new bindings please.
>
> ack.
>
> > > +%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.
>
> The device can report temperature in Celsius or Fahrenheit and that
> should be decided once. Hmm but now that I think about this, the iio
> standard attributes expect the value to be reported in milli degrees
> Celsius so I guess I should just drop this and don't report in
> Fahrenheit. Would this be ok Jonathan?
>
> > > +    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
>
> got it.
>
> > > +
> > > +  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:
> > > +      - $ref: /schemas/types.yaml#/definitions/uint32
> > > +      - minimum: 0
> > > +      - maximum: 2
> >
> > Drop the '-' on the last entry (making the min/max a single schema).
>
> got it.
>
> > > +
> > > +  '#address-cells':
> > > +    const: 1
> > > +
> > > +  '#size-cells':
> > > +    const: 0
> > > +
> > > +patternProperties:
> > > +  ".*@([1-9]|1[0-9]|20)$":
> >
> > '.*' 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)$'. This needs
> > to be at the same level.
>
> You mean dropping "patternProperties" and having "^thermocouple@.*": on
> the same indent as ".*@([1-9]|1[0-9]|20)$":? It seems to be only one

Yes.

> working. I understood and tried something like:
>
> patternProperties:
>   "@([1-9]|1[0-9]|20)$":
>    (...)
>
>    patternProperties:

What you are saying here is you have a patternProperty called 'patternProperty'.

>      "^thermocouple@.*"

And then this is not a valid json-schema keyword for the property's schema.

>      description: "..."
>      type: object
>      properties:
>      (...)
>
> But this throws "'^thermocouple@' is not one of ['$ref',
> 'additionalItems', 'additionalProperties', 'allOf', 'anyOf', 'const',
> 'contains', 'default', 'dependencies', 'deprecated', 'description',
> 'else', 'enum', 'items', 'if', 'minItems', 'minimum', 'maxItems',
> 'maximum', 'not', 'oneOf', 'pattern', 'patternProperties',
> 'properties', 'required', 'then', 'type', 'typeSize']"
>
> Also, should I also drop the ".*" in "^thermocouple@.*"?

Yes.

> > > +        type: object
> > > +        description: |
> >
> > You can drop the '|' where you don't need any formatting.
>
> got it.
>
> > > +          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.
>
> And how could I add meaning to the values. Could I add all in the
> "parent" node?

No, they have to be at the correct level. You can keep the
descriptions here. Just do:

adi,sensor-type:
 description: ...
 $ref: /schemas/types.yaml#/definitions/uint32

under ".*@([1-9]|1[0-9]|20)$" and drop the 'allOf: [ $ref: ...]' part.

>
> > > +              - 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.
>
> This device support very high resolutions (so we have fractional
> values). That is why I'm multiplying by 1000000 and using nV. And even
> so, I already loose some bits. The 64bits are needed mainly because of
> the Temperature and again the resolution I want to maximize. Doing
> int(max(temp)) * 1000000, we need 64bits.
>
> >
> > > +              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'
>
> I was aware of this but I do not know how to proceed so I was waiting
> for your comment. I do have negative values, so uint does not apply.
> What can I use here?
>
> > 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).
>
> I reinforce that I do need signed values here.

I can add those as well. At least for now, they are going to end up
being the exact same definition because IIRC while dtc takes signed
input, that's lost by the time we emit the output.

>
> >
> > > +            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.
>
> got it.
>
> > > +              - 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.
>
> Would you prefer to have something like "custom-rtd", "custom-
> thermoucouple" and so on? I would have to adapt the code but I don't
> think it would need to much of a change.

I don't really know enough about this device to say... What does
'custom' mean here?

>
> > > +            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
> > > +
>
> If I'm to replace this property as proposed before, would it make sense
> also to split this in custom-thermistor and custom-steinhart or just
> steinhart?

Seems like it as the data is completely different.

>
> > > +        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.
>
> I do need a 64-bit variable here. Should I still remove the $ref or how
> can I proceed?

We could add -milli-ohms. According to the datasheet, it's 0-131kohms
in 1/1024ohm steps.

Rob