linux-kernel - Re: [PATCH v2 7/8] dt-bindings: iio: adc: add adi,ad7606c-{16,18} compatible strings

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Message-ID: <7cd270b3-9df3-41a6-82ee-43bab78f379b@baylibre.com>
Date: Mon, 2 Sep 2024 14:58:56 -0500
From: David Lechner <dlechner@...libre.com>
To: Alexandru Ardelean <aardelean@...libre.com>,
 Krzysztof Kozlowski <krzk@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, jic23@...nel.org, krzk+dt@...nel.org,
 robh@...nel.org, lars@...afoo.de, michael.hennerich@...log.com,
 gstols@...libre.com
Subject: Re: [PATCH v2 7/8] dt-bindings: iio: adc: add adi,ad7606c-{16,18}
 compatible strings

On 9/2/24 1:38 PM, Alexandru Ardelean wrote:
> On Mon, Sep 2, 2024 at 2:55 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>
>> On Mon, Sep 02, 2024 at 01:36:30PM +0300, Alexandru Ardelean wrote:
>>>    reg:
>>> @@ -114,6 +118,25 @@ properties:
>>>        assumed that the pins are hardwired to VDD.
>>>      type: boolean
>>>
>>> +patternProperties:
>>> +  "^channel@([0-7])$":
>>> +    type: object
>>> +    $ref: adc.yaml
>>> +    unevaluatedProperties: false
>>> +
>>> +    properties:
>>> +      reg:
>>> +        description: The channel number.
>>> +        minimum: 0
>>> +        maximum: 7
>>> +
>>> +      diff-channels: true
>>
>> Shouldn't this be specific?
> 
> Umm.
> Specific how?
> Like if:then check for certain compatible strings?
> 

diff-channels is not a boolean property, it is an array of two
integers that specify the positive and negative pins. So this
should have e.g. minimum: and maximum: constraints for each
item in the array. Even if we only use this like a boolean flag
in the driver, we need to make the bindings use the already
established definition of diff-channels from adc.yaml.

It would look like this in the .dts:

    diff-channels = <1 1>;

The datasheet numbers the pins 1 to 8 instead of 0 to 7,
so it would make sense to have the pin number be reg + 1
(or redefine reg to be minimum: 1, maximum: 8).

We also recently introduced a single-channel property
that can be used when the pin number of of the input
doesn't match the reg number.

>>
>>> +
>>> +      bipolar: true
>>> +
>>> +    required:
>>> +      - reg
>>> +
>>>  required:
>>>    - compatible
>>>    - reg
>>> @@ -202,4 +225,44 @@ examples:
>>>              standby-gpios = <&gpio 24 GPIO_ACTIVE_LOW>;
>>>          };
>>>      };
>>> +  - |
>>> +    #include <dt-bindings/gpio/gpio.h>
>>> +    #include <dt-bindings/interrupt-controller/irq.h>
>>> +    spi {
>>> +        #address-cells = <1>;
>>> +        #size-cells = <0>;
>>> +
>>> +        adc@0 {
>>> +            compatible = "adi,ad7606c-18";
>>> +            reg = <0>;
>>> +            spi-max-frequency = <1000000>;
>>> +            spi-cpol;
>>> +            spi-cpha;
>>> +
>>> +            avcc-supply = <&adc_vref>;
>>> +            vdrive-supply = <&vdd_supply>;
>>> +
>>> +            interrupts = <25 IRQ_TYPE_EDGE_FALLING>;
>>> +            interrupt-parent = <&gpio>;
>>> +
>>> +            adi,conversion-start-gpios = <&gpio 17 GPIO_ACTIVE_HIGH>;
>>> +
>>> +            adi,conversion-start-gpios = <&gpio 17 GPIO_ACTIVE_HIGH>;
>>> +            reset-gpios = <&gpio 27 GPIO_ACTIVE_HIGH>;
>>> +            adi,first-data-gpios = <&gpio 22 GPIO_ACTIVE_HIGH>;
>>> +            standby-gpios = <&gpio 24 GPIO_ACTIVE_LOW>;
>>> +
>>> +            adi,sw-mode;
>>> +
>>> +            channel@1 {
>>> +                reg = <1>;
>>> +                diff-channel;
>>
>> Where is this property defined (which schema)?
>>
>> Did you test it?
> 
> Tested on my board.
> But forgot to update the DT schema docs.
> Though, if you're referring to testing it somehow via some make
> command, I'm a little behind on how all this works now.
> I'll go re-check the "make dtbs_check" and similar commands.
> 
> Maybe I sound a bit old (now), but when I last saw these DT bindings
> going from txt-to-yaml, they seemed relatively simple.
> Now, they're almost like their own programming language.
> I'll search for some quick setup guides for these; any pointers are welcome :)

I can help you with this.