Re: [PATCH 2/2] dt-bindings: iio: dac: Add DAC8163

[David Lechner <dlechner@baylibre.com>]

It is more logical to put the dt-bindings patch first in the series
before the driver that makes use of it.

On 6/23/26 11:07 AM, Lukas Metz wrote:
> Add device tree binding for the Texas Instruments DAC8163 family
> including the DAC7562, DAC7563, DAC8162, DAC8163, DAC8562 and DAC8563.
> 
> Signed-off-by: Lukas Metz <lukas.metz@gmx.net>
> ---
>  .../devicetree/bindings/iio/dac/ti,dac8163.yaml    | 75 ++++++++++++++++++++++
>  MAINTAINERS                                        |  1 +
>  2 files changed, 76 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/ti,dac8163.yaml b/Documentation/devicetree/bindings/iio/dac/ti,dac8163.yaml
> new file mode 100644
> index 000000000000..bb4bad389323
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/ti,dac8163.yaml
> @@ -0,0 +1,75 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/dac/ti,dac8163.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Texas Instruments DAC8163 family of DACs
> +
> +description:
> +  The DAC756x, DAC816x, and DAC856x devices are low-power, voltage-output,
> +  dual-channel, 12-, 14-, and 16-bit digital-to-analog converters (DACs),
> +  respectively. These devices include a 2.5-V, 4-ppm/°C internal
> +  reference, giving a full-scale output voltage range of 2.5 V or 5 V.
> +
> +maintainers:
> +  - Lukas Metz <lukas.metz@gmx.net>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - ti,dac7562
> +      - ti,dac7563
> +      - ti,dac8162
> +      - ti,dac8163
> +      - ti,dac8562
> +      - ti,dac8563
> +
> +  reg:
> +    maxItems: 1
> +

There are a couple of more SPI properties needed since this is not a "normal"
SPI device. We can only write and not read because there is no D_OUT pin. So

spi-rx-bus-width:
  items:
    - const: 0

will describe this.

There is also no chip select, but now that I am looking, there doesn't seem to
be anything to describe this.

> +  ti,loaddacs-gpios:

This should match the actual pin name. And we don't need vendor prefix on gpios.
So `ldac-gpios`.

We also want the binding to be complete even if the driver doesn't all of it, so
`clear-gpios` and `sync-gpios` probably make sense too.

Usually for SPI devices we also add:

spi-max-frequency:
  maximum: ...

> +    description:
> +      Pin needs to be asserted permanently when updating the DAC synchronously.
> +    maxItems: 1
> +
> +  vref-supply:
> +    description:
> +      Reference voltage for scaling if an external reference is used.

I prefer to use the actual pin name, i.e. vrefin-supply.

And for the description, it is the actual external reference voltage
supply, not just the voltage.

And we also need `avdd-supply: true`.

> +
> +  ti,internal-ref:
> +    type: boolean
> +    description:
> +      Flag if the internal reference is used (external otherwise).

Usually, we don't bother with a property like this since it is redundant.
If an external reference supply is given, then it gets used, otherwise
the internal reference is used.

> +
> +required:
> +  - compatible
> +  - reg

avdd-supply will be required too

> +
> +allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> +  - if:
> +      not:
> +        required:
> +          - ti,internal-ref
> +    then:
> +      required:
> +        - vref-supply
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        dac@1 {
> +            compatible = "ti,dac8163";
> +            reg = <0x1>; /* CS1 */

These chips don't appear to have a chip select pin, so this comment
doesn't make sense to me. More logical would be to just use dac@0
and reg = <0>; since it should just be ignored.

> +            ti,loaddacs-gpios = <&gpiog 8 GPIO_ACTIVE_HIGH>;

The pin is marked active low in the datasheet, so I would expect
this to be GPIO_ACTIVE_LOW.

> +            ti,internal-ref; /* internal reference used*/
> +        };
> +    };
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e82cc28e1bc3..5512f5eaab44 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -26398,6 +26398,7 @@ TI DAC8163 DAC DRIVER
>  M:	Lukas Metz <lukas.metz@gmx.net>
>  L:	linux-iio@vger.kernel.org
>  S:	Maintained
> +F:	Documentation/devicetree/bindings/iio/dac/ti,dac8163.yaml
>  F:	drivers/iio/dac/ti-dac8163.c
>  
>  TI DATA TRANSFORM AND HASHING ENGINE (DTHE) V2 CRYPTO DRIVER
>