Re: [PATCH 4/5] dt-bindings: iio: Add sx9324 binding

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 30 Oct 2021 04:18:26 -0700
Gwendal Grignou <gwendal@chromium.org> wrote:

> Similar to SX9310, add biddings to setup sx9324 hardware properties.
> SX9324 is a little different, introduce 4 phases to be configured in 2
> pairs over 3 antennas.
> 
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
This has a high degree of black magic.

I'm curious - is there a fairly heavy weight userspace library interpreting
the various readings?  If so I don't suppose it's available anywhere to look at?
If you can point to any public info on this part that would also be great.

Thanks,

Jonathan

> ---
>  .../iio/proximity/semtech,sx9324.yaml         | 141 ++++++++++++++++++
>  1 file changed, 141 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml b/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml
> new file mode 100644
> index 0000000000000..fe9edf15c16d4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml
> @@ -0,0 +1,141 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/proximity/semtech,sx9310.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Semtech's SX9324 capacitive proximity sensor
> +
> +maintainers:
> +  - Gwendal Grignou <gwendal@chromium.org>
> +  - Daniel Campello <campello@chromium.org>
> +
> +description: |
> +  Semtech's SX9324 proximity sensor.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - semtech,sx9324x
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    description:
> +      The sole interrupt generated by the device used to announce the
> +      preceding reading request has finished and that data is
> +      available or that a close/far proximity event has happened.
No need to say sole given maxItems: 1
Perhaps...

	Generated by device to announce preceding read request has finished
	and data is available or that a close/far proximity event has happened.

> +    maxItems: 1
> +
> +  vdd-supply:
> +    description: Main power supply
> +
> +  svdd-supply:
> +    description: Host interface power supply
> +
> +  "#io-channel-cells":
> +    const: 1

Curious -  Do we have consumers of this?

> +
> +  semtech,ph0-pin:
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description: |
> +      Indicates how each CS pin is used during phase 0.
> +      Each of the 3 pins have the following value -
> +      0 : unused (high impedance)
> +      1 : measured input
> +      2 : dynamic shield
> +      3 : grounded.
> +      For instance, CS0 measured, CS1 shield and CS2 ground is [1, 2, 3]
> +    items:
> +      enum: [ 0, 1, 2, 3 ]
> +    minItems: 3
> +    maxItems: 3
> +
> +  semtech,ph1-pin:
> +  semtech,ph2-pin:
> +  semtech,ph3-pin:
> +    Same as ph0-pin

I'm curious - why would you chose different combinations?  I guess because of
different wiring.  If that's the case, is there a documented 'right' choice
for a given wiring.   I'm just wondering if we are better off describing
what is connected to these pins and having the driver pick a valid control
sequence.  That might simplify things.  If not then fair enough.

> +
> +  semtech,resolution01
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    enum: [0, 1, 2, 3, 4, 5, 6, 7]
> +    description:
> +      Capacitance measurement resolution. For phase 0 and 1.
> +      Higher the number, higher the resolution.

Can we not give something more meaningful than high is higher?
I don't have the datasheet for this part and the 9330 that I'm
looking at is rather unhelpful on this.  I have no idea how anyone
using that datasheet would figure out what to set this to!

> +    default: 4
> +
> +  semtech,resolution23
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    enum: [0, 1, 2, 3, 4, 5, 6, 7]
> +    description:
> +      Capacitance measurement resolution. For phase 2 and 3
> +    default: 4
> +
> +  semtech,startup-sensor:
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    enum: [0, 1, 2, 3]
> +    default: 0
> +    description:
> +      Phase used for start-up proximity detection.
> +      It is used when we enable a phase to remove static offset and measure
> +      only capacitance changes introduced by the user.
> +
> +  semtech,proxraw-strength01:
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    enum: [0, 1, 2, 3, 4, 5, 6, 7]
> +    default: 1
> +    description:
> +      PROXRAW filter strength for phase 0 and 1. A value of 0 represents off,i
> +      and other values represent 1-1/N.
> +
> +  semtech,proxraw-strength23:
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    enum: [0, 1, 2, 3, 4, 5, 6, 7]
> +    default: 1
> +    description:
> +      PROXRAW filter strength for phase 2 and 3. A value of 0 represents off,i
> +      and other values represent 1-1/N.
> +
> +  semtech,avg-pos-strength:
> +    $ref: /schemas/types.yaml#definitions/uint32
> +    enum: [0, 16, 64, 128, 256, 512, 1024, 4294967295]
> +    default: 16
> +    description:
> +      Average positive filter strength. A value of 0 represents off and
> +      UINT_MAX (4294967295) represents infinite. Other values
> +      represent 1-1/N.
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#io-channel-cells"
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +    i2c {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      proximity@28 {
> +        compatible = "semtech,sx9310";
> +        reg = <0x28>;
> +        interrupt-parent = <&pio>;
> +        interrupts = <5 IRQ_TYPE_LEVEL_LOW 5>;
> +        vdd-supply = <&pp3300_a>;
> +        svdd-supply = <&pp1800_prox>;
> +        #io-channel-cells = <1>;
> +        semtech,ph0-pin = <1, 2, 3>;
> +        semtech,ph1-pin = <3, 2, 1>;
> +        semtech,ph2-pin = <1, 2, 3>;
> +        semtech,ph3-pin = <3, 2, 1>;
> +        semtech,resolution01 = 2;
> +        semtech,resolution23 = 2;
> +        semtech,startup-sensor = <1>;
> +        semtech,proxraw-strength01 = <2>;
> +        semtech,proxraw-strength23 = <2>;
> +        semtech,avg-pos-strength = <64>;
> +      };
> +    };