Message-ID: <20241114-popsicle-trump-39fb46d7eec0@spud>
Date: Thu, 14 Nov 2024 19:55:53 +0000
From: Conor Dooley <conor@...nel.org>
To: Ciprian Hegbeli <ciprian.hegbeli@...log.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Javier Carrasco <javier.carrasco.cruz@...il.com>,
	Kim Seer Paller <kimseer.paller@...log.com>,
	Antoniu Miclaus <antoniu.miclaus@...log.com>,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: iio: frequency: Add ADF4382

On Thu, Nov 14, 2024 at 03:03:10PM +0200, Ciprian Hegbeli wrote:
> The ADF4382A is a high performance, ultralow jitter, Frac-N PLL
> with integrated VCO ideally suited for LO generation for 5G applications
> or data converter clock applications. The high performance
> PLL has a figure of merit of -239 dBc/Hz, low 1/f Noise and
> high PFD frequency of 625MHz in integer mode that can achieve
> ultralow in-band noise and integrated jitter. The ADF4382A can
> generate frequencies in a fundamental octave range of 11.5 GHz to
> 21 GHz, thereby eliminating the need for sub-harmonic filters. The
> divide by 2 and 4 output dividers on the part allow frequencies to
> be generated from 5.75GHz to 10.5GHz and 2.875GHz to 5.25GHz
> respectively.
> 
> Signed-off-by: Ciprian Hegbeli <ciprian.hegbeli@...log.com>
> ---
>  .../bindings/iio/frequency/adi,adf4382.yaml   | 141 ++++++++++++++++++
>  1 file changed, 141 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/frequency/adi,adf4382.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/frequency/adi,adf4382.yaml b/Documentation/devicetree/bindings/iio/frequency/adi,adf4382.yaml
> new file mode 100644
> index 000000000000..44a29ac7a2e8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/frequency/adi,adf4382.yaml
> @@ -0,0 +1,141 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/frequency/adi,adf4382.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ADF4382 Microwave Wideband Synthesizer with Integrated VCO
> +
> +maintainers:
> +  - Antoniu Miclaus <antoniu.miclaus@...log.com>
> +  - Ciprian Hegbeli <ciprian.hegbeli@...log.com>
> +
> +description: The ADF4382 is a high performance, ultralow jitter, Frac-N PLL with
> +   integrated VCO ideally suited for LO generation for 5G applications
> +   or data converter clock applications.
> +
> +   https://www.analog.com/en/products/adf4382a.html
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,adf4382
> +      - adi,adf4382a
> +
> +  reg:
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 75000000
> +
> +  clocks:
> +    description: Clock to provide CLKIN reference clock signal.
> +    maxItems: 1

All you need here is:

clocks:
  items:
    - description: foo

> +
> +  clock-names:
> +    description:
> +      External clock that provides reference input frequency.

Drop the description, you have one above.

> +    items:
> +      - const: ref_clk
> +
> +  '#clock-cells':
> +    const: 0
> +
> +  clock-output-names:
> +    maxItems: 1
> +
> +  adi,charge-pump-microamp:
> +    description:
> +      The charge pump current that the external loop filter was designed for.
> +      If this property is not specified, then the charge pump current is set to the
> +      default 11100uA. The valid values are listed below. However, if the set value is
> +      not supported, the driver will look for the closest valid charge pump current.
> +    anyOf:
> +      - enum: [790, 990, 1190, 1380, 1590, 1980, 2390, 2790, 3180, 3970, 4770, 5570, 6330, 7910, 9510, 11100]

Just enum, drop the anyof.

> +
> +  adi,ref-divider:
> +    description:
> +      Input divider of the reference frequency, cannot be lower then 1 or
> +      higher then 63.
> +    allOf:

This allof isn't required, all these can move up a level. Not entirely
sure why this is actually required though, shouldn't the driver be able
to compute this based on the output frequency requested?

> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +      - minimum: 1
> +      - maximum: 63
> +      - default: 1

> +    maxItems: 1

drop this.


> +
> +  adi,ref-doubler-enable:
> +    description:
> +      Enables the doubling of the reference clock.
> +    type: boolean

type: flag
but same question here about why this is in the binding.

> +    maxItems: 1
> +
> +  adi,bleed-word:
> +    description:
> +      A small programmable constant charge pump current, known as bleed current,
> +      can be used to optimize the phase noise and fractional spurious signals
> +      in fractional mode.
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +      - minimum: 0
> +      - maximum: 4095
> +      - default: 0
> +    maxItems: 1

Same comments about allOf/maxItems here. Additionally, why is this in
the binding, and not something controllable from userspace etc?
If it stays in the binding, why "bleed-word" and not
"bleed-current-microamps" (or w/e other unit that is more appropriate)

> +
> +  adi,power-up-frequency:
> +    description:
> +      PLL tunes to the set frequency on probe or defaults to 2,305 GHz.
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint64
> +      - minimum: 687500000
> +      - maximum: 22000000000
> +      - default: 2305000000
> +    maxItems: 1

Same comments here.

> +
> +  adi,output-power-value:
> +    description:
> +      The output power amplitude level which will be applied for both channels
> +      at startup.
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +      - minimum: 0
> +      - maximum: 15
> +      - default: 11
> +    maxItems: 1

Is this a unitless gain or a power that should have a unit?
Same comments as other properties about allOf/anyOf.

> +
> +  adi,spi-3wire-enable:

spi-3wire is a standard property

> +    description:
> +      Uses SPI in 3 wire mode, by default is uses 4 wire mode.
> +    type: boolean
> +    maxItems: 1
> +
> +  adi,cmos-3v3:
> +    description:
> +      Sets the SPI logic to 3.3V, by defautl it uses 1,8V.
> +    type: boolean
> +    maxItems: 1

type: flag. Drop the maxItems.

Cheers,
Conor.

> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-names
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        frequency@0 {
> +          compatible = "adi,adf4382";
> +          reg = <0>;
> +          spi-max-frequency = <1000000>;
> +          clocks = <&adf4382_clkin>;
> +          clock-names = "ref_clk";
> +          adi,charge-pump-current = <15>;
> +          adi,ref-divider = <1>;
> +        };
> +    };
> +...
> -- 
> 2.43.0
> 

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