linux-kernel - Re: [PATCH 1/2] dt-bindings: hwmon: Add DT bindings for TI ads1000/ads1100 ADCs

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Date:   Thu, 13 Jun 2019 14:33:13 -0600
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Corbet <corbet@....net>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: hwmon: Add DT bindings for TI
 ads1000/ads1100 ADCs

On Wed, May 15, 2019 at 01:58:08AM +0300, Serge Semin wrote:
> Add dt-binding documentation for the Texas Instruments ads1000/ads1100 ADCs
> driver.
> 
> Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> ---
>  .../devicetree/bindings/hwmon/ads1000.txt     | 61 ++++++++++++++++

Bindings should be separate patch.

>  Documentation/hwmon/ads1000.rst               | 72 +++++++++++++++++++
>  2 files changed, 133 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/ads1000.txt
>  create mode 100644 Documentation/hwmon/ads1000.rst
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/ads1000.txt b/Documentation/devicetree/bindings/hwmon/ads1000.txt
> new file mode 100644
> index 000000000000..3907b7da9b33
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/ads1000.txt
> @@ -0,0 +1,61 @@
> +ADS1000/ADS1100 (I2C)
> +
> +This device is a 12-16 bit A-D converter with 1 input.

ADC's should be in bindings/iio/adc/

> +
> +The inputs can be used either as a differential pair of Vin+ Vin- or as a single
> +ended sensor for Vin+ GND. The inputs mode is platform-dependent and isn't
> +configured by software in any case.
> +
> +Device A-D converter sensitivity can be configured using two parameters:
> + - pga is the programmable gain amplifier
> +    0: x1 (default) 
> +    1: x2
> +    2: x4
> +    3: x8
> + - data_rate in samples per second also affecting the output code accuracy
> +    0: 128SPS - +/- Vdd*0.488mV (default, ads1000 accepts this rate only)
> +    1: 32SPS  - +/- Vdd*0.122mV
> +    2: 16SPS  - +/- Vdd*0.061mV
> +    3: 8SPS   - +/- Vdd*0.030mV
> +   Since this parameter also affects the output accuracy, be aware the greater
> +   SPS the worse accuracy.
> +
> +As a result the output value is calculated by the next formulae:
> +dVin = Cod * Vdd / (PGA * max(|Cod|)), where
> +max(|Cod|) - maximum possible value of the output code, which depends on the SPS
> +setting from the table above.
> +
> +The ADS1000/ADS1100 dts-node:
> +
> +  Required properties:
> +   - compatible : must be "ti,ads1000" or "ti,ads1100"
> +   - reg : I2C bus address of the device
> +   - #address-cells : must be <1>
> +   - #size-cells : must be <0>
> +   - vdd-supply : regulator for reference supply voltage (usually fixed)
> +
> +  Optional properties:
> +   - ti,gain : the programmable gain amplifier setting
> +   - ti,datarate : the converter data rate

IIRC, we have standard properties for these.

> +   - ti,voltage-divider : <R1 R2> Ohms inbound voltage dividers,
> +     so dVin = (R1 + R2)/R2 * dVin
> +
> +Example:
> +
> +vdd_5v0: fixedregulator@0 {
> +	compatible = "regulator-fixed";
> +	regulator-name = "vdd-ref";
> +	regulator-min-microvolt = <5000000>;
> +	regulator-max-microvolt = <5000000>;
> +	regulator-always-on;
> +};
> +
> +tiadc: ads1000@48 {

adc@48

> +	compatible = "ti,ads1000";
> +	reg = <0x48>;
> +
> +	vdd-supply = <&vdd_5v0>;
> +	ti,gain = <0>;
> +	ti,voltage-divider = <31600 3600>;
> +};
> +