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Date: Sun, 10 Oct 2021 15:48:56 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Mihail Chindris <mihail.chindris@...log.com>
Cc: <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
<lars@...afoo.de>, <Michael.Hennerich@...log.com>,
<nuno.sa@...log.com>, <dragos.bogdan@...log.com>,
<alexandru.ardelean@...log.com>, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v2 1/2] dt-bindings: iio: dac: Add adi,ad3552r.yaml
On Fri, 8 Oct 2021 12:39:08 +0000
Mihail Chindris <mihail.chindris@...log.com> wrote:
> Add documentation for ad3552r
>
> Signed-off-by: Mihail Chindris <mihail.chindris@...log.com>
Hi Mihael,
A few comments inline.
Thanks,
Jonathan
> ---
> .../bindings/iio/dac/adi,ad3552r.yaml | 199 ++++++++++++++++++
> 1 file changed, 199 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
>
> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> new file mode 100644
> index 000000000000..1086e935d330
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> @@ -0,0 +1,199 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +# Copyright 2020 Analog Devices Inc.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/dac/adi,ad3552r.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices AD2552R DAC device driver
> +
> +maintainers:
> + - Mihail Chindris <mihail.chindris@...log.com>
> +
> +description: |
> + Bindings for the Analog Devices AD3552R DAC device. Datasheet can be
Extra space before DAC, and doesn't mention the other supported part.
One option to avoid a never ending list is "and similar."
> + found here:
> + https://www.analog.com/media/en/technical-documentation/data-sheets/ad3552r.pdf
Good to have datasheet for the other part as well as I don't think this is a shared
datasheet?
> +
> +properties:
> + compatible:
> + enum:
> + - adi,ad3552r
> + - adi,ad3542r
Alphabetical order preferred.
> +
> + reg:
> + maxItems: 1
> +
> + spi-max-frequency:
> + maximum: 30000000
> +
> + reset-gpios:
> + maxItems: 1
> +
> + ldac-gpios:
> + description: |
> + If a LDAC gpio is specified it will generate a LDAC pulse each time the
> + trigger handler sends data to the chip.
Trigger handler is a linux concept. You need to write this more generically.
Something like.
"LDAC pin is used as a hardware trigger to update a set of DACs."
> + maxItems: 1
> +
> + vref-supply:
> + description:
> + The regulator to use as an external reference. If it does not exists the
> + internal reference will be used. External reference must be 2.5V
> +
> + adi,vref-out-en:
> + description: Vref I/O driven by internal vref to 2.5V. If not set, Vref pin
> + will be floating.
> + type: boolean
> +
> + adi,sdo-drive-strength:
> + description: |
> + Configure SDIO0 and SDIO1 strength levels:
> + - 0: low SDO drive strength.
> + - 1: medium low SDO drive strength.
> + - 2: medium high SDO drive strength.
> + - 3: high SDO drive strength
> + $ref: /schemas/types.yaml#/definitions/uint32
> + enum: [0, 1, 2, 3]
> +
> +patternProperties:
> + "^channel@([0-1])$":
> + type: object
> + description: Configurations of the DAC Channels
> + properties:
> + reg:
> + description: Channel number
> + enum: [0, 1]
> +
> + custom-output-range-config:
Not a generic property so I think this needs an adi prefix.
> + type: object
> + description: Configuration of custom range when
> + adi,output-range-microvolt is not present.
> + The formulas for calculation the output voltages are
> + Vout_fs = 2.5 + [(GainN + Offset/1024) * 2.5 * Rfbx * 1.03]
> + Vout_zs = 2.5 - [(GainP + Offset/1024) * 2.5 * Rfbx * 1.03]
> + properties:
> + adi,gain-offset:
> + description: Gain offset used in the above formula
> + $ref: /schemas/types.yaml#/definitions/int32
> + maximum: 511
> + minimum: -511
> + adi,gain-scaling-p:
> + description: |
> + Scaling p:
> + 0: 1.0
> + 1: 0.5
> + 2: 0.25
> + 3: 0.125
Given this is just a mapping to a simple set of values, could we just have
the values or express it as 1/(2^GainP) in the equation above and call it
adi,gain-scalling-inv-log2 or something like that?
If we can avoid a mapping table that is always a nice to have
> + $ref: /schemas/types.yaml#/definitions/uint32
> + enum: [0, 1, 2, 3]
> + adi,gain-scaling-n:
> + description: |
> + Scaling p:
> + 0: 1.0
> + 1: 0.5
> + 2: 0.25
> + 3: 0.125
> + $ref: /schemas/types.yaml#/definitions/uint32
> + enum: [0, 1, 2, 3]
> + adi,rfb-ohms:
> + description: Feedback Resistor
> + required:
> + - adi,gain-offset
> + - adi,gain-sacling-p
> + - adi,gain-sacling-n
> + - adi,rfb-ohms
> + required:
> + - reg
> +
> + oneOf:
> + # If adi,output-range is missing, custom-output-range-config must be used
adi,output-range-microvolt is missing...
> + - required:
> + - adi,output-range-microvolt
> + - required:
> + - custom-output-range-config
> +
> +allOf:
> + - if:
> + properties:
> + compatible:
> + contains:
> + const: adi,ad3542r
> + then:
> + patternProperties:
> + "^channel@([0-1])$":
> + type: object
> + properties:
> + adi,output-range-microvolt:
> + description: |
> + Voltage output range of the channel as <minimum, maximum>
> + Required connections:
> + Rfb1x for: 0 to 2.5 V; 0 to 3V; 0 to 5 V;
> + Rfb2x for: 0 to 10 V; 2.5 to 7.5V; -5 to 5 V;
> + oneOf:
> + - items:
> + - const: 0
> + - enum: [2500000, 3000000, 5000000, 10000000]
> + - items:
> + - const: -2500000
> + - const: 7500000
> + - items:
> + - const: -5000000
> + - const: 5000000
> + required:
> + - adi,output-range-microvolt
> + - if:
> + properties:
> + compatible:
> + contains:
> + const: adi,ad3552r
> + then:
> + patternProperties:
> + "^channel@([0-1])$":
> + type: object
> + properties:
> + adi,output-range-microvolt: |
> + Voltage output range of the channel as <minimum, maximum>
> + Required connections:
> + Rfb1x for: 0 to 2.5 V; 0 to 5 V;
> + Rfb2x for: 0 to 10 V; -5 to 5 V;
> + Rfb4x for: -10 to 10V
> + oneOf:
> + - items:
> + - const: 0
> + - enum: [2500000, 5000000, 10000000]
> + - items:
> + - const: -5000000
> + - const: 5000000
> + - items:
> + - const: -10000000
> + - const: 10000000
> +
> +required:
> + - compatible
> + - reg
> + - spi-max-frequency
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + ad3552r {
> + compatible = "adi,ad3552r";
> + reg = <0>;
> + spi-max-frequency = <20000000>;
> + channel@0 {
> + reg = <0>;
> + adi,output-range-microvolt = <0 10000000>;
> + };
> + channel@1 {
> + reg = <1>;
> + custom-output-range-config {
> + adi,gain-offset = <5>;
> + adi,gain-scaling-p = <1>;
> + adi,gain-scaling-n = <2>;
> + adi,rfb-ohms = <1>;
> + };
> + };
> + };
> +...
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