On Sat, Jul 03, 2021 at 07:34:56PM +0200, Linus Walleij wrote: > This converts the NTC thermistor DT bindings to YAML. Some care had to > be taken since I had to add some illustrations to make the connection > layouts graspable. > > Cc: Javier Martinez Canillas <javier@xxxxxxxxxxxx> > Cc: Johannes Pointner <johannes.pointner@xxxxxxxxx> > Cc: Peter Rosin <peda@xxxxxxxxxx> > Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > Cc: devicetree@xxxxxxxxxxxxxxx > Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > --- > ChangeLog v1->v2: > - Realize I need to CC devicetree@xxxxxxxxxxxxxxx on this. > - Fix Javier's mail address. > - Drop Naveen's mail (bouncing) > --- > .../bindings/hwmon/ntc-thermistor.yaml | 142 ++++++++++++++++++ > .../bindings/hwmon/ntc_thermistor.txt | 44 ------ > 2 files changed, 142 insertions(+), 44 deletions(-) > create mode 100644 Documentation/devicetree/bindings/hwmon/ntc-thermistor.yaml > delete mode 100644 Documentation/devicetree/bindings/hwmon/ntc_thermistor.txt > > diff --git a/Documentation/devicetree/bindings/hwmon/ntc-thermistor.yaml b/Documentation/devicetree/bindings/hwmon/ntc-thermistor.yaml > new file mode 100644 > index 000000000000..87589da631c9 > --- /dev/null > +++ b/Documentation/devicetree/bindings/hwmon/ntc-thermistor.yaml > @@ -0,0 +1,142 @@ > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > +--- > +$id: http://devicetree.org/schemas/hwmon/ntc-thermistor.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: NTC thermistor temperature sensors > + > +maintainers: > + - Naveen Krishna Chatradhi <ch.naveen@xxxxxxxxxxx> > + - Linus Walleij <linus.walleij@xxxxxxxxxx> > + > +description: | > + Thermistors with negative temperature coefficient (NTC) are resistors that > + vary in resistance in an often non-linear way in relation to temperature. > + The negative temperature coefficient means that the resistance decreases > + as the temperature rises. Since the relationship between resistance and > + temperature is non-linear, software drivers most often need to use a look > + up table and interpolation to get from resistance to temperature. > + > + When used in practice, a thermistor is often connected between ground, a > + pull-up resistor or/and a pull-down resistor and a fixed voltage like this: > + > + + e.g. 5V = pull-up voltage (puv) > + | > + +-+ > + | | > + | | Pull-up resistor > + | | (puo) > + +-+ > + |-------------------------o > + +-+ | ^ > + | |/ | > + | / | > + |/| Thermistor | Measured voltage (mv) > + / | | "connected ground" > + /| | | > + +-+ | > + |-------------------------o > + +-+ ^ > + | | | > + | | Pull-down resistor | Measured voltage (mv) > + | | (pdo) | "connected positive" > + +-+ | > + | | > + | v > + + GND GND > + > + The arrangements of where we measure the voltage over the thermistor are > + called "connected ground" and "connected positive" and shall be understood as > + the cases when either pull-up or pull-down resistance is zero. > + > + If the pull-up resistance is 0 one end of the thermistor is connected to the > + positive voltage and we get the thermistor on top of a pull-down resistor > + and we take the measure between the thermistor and the pull-down resistor. > + > + Conversely if the pull-down resistance is zero, one end of the thermistor is > + connected to ground and we get the thermistor under the pull-up resistor > + and we take the measure between the pull-up resistor and the thermistor. > + > + We can use both pull-up and pull-down resistors at the same time, and then > + the figure illustrates where the voltage will be measured for the "connected > + ground" and "connected positive" cases. > + > +properties: > + $nodename: > + pattern: "^thermistor(.*)?$" > + > + compatible: > + oneOf: > + - const: epcos,b57330v2103 > + - const: epcos,b57891s0103 > + - const: murata,ncp15wb473 > + - const: murata,ncp18wb473 > + - const: murata,ncp21wb473 > + - const: murata,ncp03wb473 > + - const: murata,ncp15wl333 > + - const: murata,ncp03wf104 > + - const: murata,ncp15xh103 All these can be 1 enum. > + # Deprecated "ntp," compatible strings > + - const: ntc,ncp15wb473 > + deprecated: true > + - const: ntc,ncp18wb473 > + deprecated: true > + - const: ntc,ncp21wb473 > + deprecated: true > + - const: ntc,ncp03wb473 > + deprecated: true > + - const: ntc,ncp15wl333 > + deprecated: true And these too. > + > + # See /schemas/thermal/thermal-sensor.yaml for details Drop. (I hope to generate documentation from the schema and automagically create references/links.) > + "#thermal-sensor-cells": > + description: Thermal sensor cells if used for thermal sensoring. > + const: 0 > + > + pullup-uv: > + $ref: /schemas/types.yaml#/definitions/uint32 > + description: Pull-up voltage in micro volts. Must always be specified. > + > + pullup-ohm: > + $ref: /schemas/types.yaml#/definitions/uint32 > + description: Pull-up resistance in ohms. Must always be specified, even > + if zero. > + > + pulldown-ohm: > + $ref: /schemas/types.yaml#/definitions/uint32 > + description: Pull-down resistance in ohms. Must always be specified, even > + if zero. > + > + connected-positive: > + $ref: /schemas/types.yaml#/definitions/flag > + description: Indicates how the thermistor is connected in series with > + a pull-up and/or a pull-down resistor. See the description above for > + an illustration. If this flag is NOT specified, the thermistor is assumed > + to be connected-ground, which usually means a pull-down resistance of > + zero but complex arrangements are possible. > + > + # See /schemas/iio/adc/adc.yaml > + io-channels: > + maxItems: 1 > + description: IIO ADC channel to read the voltage over the resistor. Must > + always be specified. > + > +required: > + - compatible > + - pullup-uv > + - pullup-ohm > + - pulldown-ohm > + - io-channels > + > +additionalProperties: false > + > +examples: > + - | > + thermistor0 { > + compatible = "murata,ncp18wb473"; > + io-channels = <&gpadc 0x06>; > + pullup-uv = <1800000>; > + pullup-ohm = <220000>; > + pulldown-ohm = <0>; > + #thermal-sensor-cells = <0>; > + };
