RE: [PATCH v4 3/5] dt-bindings: iio: dac: Add adi,ltc2664.yaml

Paller, Kim Seer
2024-06-24T15:14:16Z

> -----Original Message-----
> From: Conor Dooley <conor@kernel.org>
> Sent: Thursday, June 20, 2024 1:57 AM
> To: Paller, Kim Seer <KimSeer.Paller@analog.com>
> Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> devicetree@vger.kernel.org; Jonathan Cameron <jic23@kernel.org>; David
> Lechner <dlechner@baylibre.com>; Lars-Peter Clausen <lars@metafoo.de>;
> Liam Girdwood <lgirdwood@gmail.com>; Mark Brown <broonie@kernel.org>;
> Dimitri Fedrau <dima.fedrau@gmail.com>; Krzysztof Kozlowski
> <krzk+dt@kernel.org>; Rob Herring <robh@kernel.org>; Conor Dooley
> <conor+dt@kernel.org>; Hennerich, Michael
> <Michael.Hennerich@analog.com>; Nuno Sá <noname.nuno@gmail.com>
> Subject: Re: [PATCH v4 3/5] dt-bindings: iio: dac: Add adi,ltc2664.yaml
>
> [External]
>
> On Wed, Jun 19, 2024 at 02:49:02PM +0800, Kim Seer Paller wrote:
> > Add documentation for ltc2664.
> >
> > Co-developed-by: Michael Hennerich <michael.hennerich@analog.com>
> > Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
> > Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
> > ---
> > .../bindings/iio/dac/adi,ltc2664.yaml | 167 ++++++++++++++++++
> > MAINTAINERS | 8 +
> > 2 files changed, 175 insertions(+)
> > create mode 100644
> > Documentation/devicetree/bindings/iio/dac/adi,ltc2664.yaml
> >
> > diff --git
> > a/Documentation/devicetree/bindings/iio/dac/adi,ltc2664.yaml
> > b/Documentation/devicetree/bindings/iio/dac/adi,ltc2664.yaml
> > new file mode 100644
> > index 000000000000..be37700e3b1f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/dac/adi,ltc2664.yaml
> > @@ -0,0 +1,167 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/dac/adi,ltc2664.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Analog Devices LTC2664 DAC
> > +
> > +maintainers:
> > + - Michael Hennerich <michael.hennerich@analog.com>
> > + - Kim Seer Paller <kimseer.paller@analog.com>
> > +
> > +description: |
> > + Analog Devices LTC2664 4 channel, 12-/16-Bit, +-10V DAC
> > +
> > +https://www.analog.com/media/en/technical-documentation/data-sheets/2
> > +664fa.pdf
> > +
> > +properties:
> > + compatible:
> > + enum:
> > + - adi,ltc2664
> > +
> > + reg:
> > + maxItems: 1
> > +
> > + spi-max-frequency:
> > + maximum: 50000000
> > +
> > + vcc-supply:
> > + description: Analog Supply Voltage Input.
> > +
> > + v-pos-supply:
> > + description: Positive Supply Voltage Input.
> > +
> > + v-neg-supply:
> > + description: Negative Supply Voltage Input.
> > +
> > + iovcc-supply:
> > + description: Digital Input/Output Supply Voltage.
> > +
> > + ref-supply:
> > + description:
> > + Reference Input/Output. The voltage at the REF pin sets the full-scale
> > + range of all channels. If not provided the internal reference is used and
> > + also provided on the VREF pin.
> > +
> > + reset-gpios:
> > + description:
> > + Active-low Asynchronous Clear Input. A logic low at this level-triggered
> > + input clears the part to the reset code and range determined by the
> > + hardwired option chosen using the MSPAN pins. The control registers are
> > + cleared to zero.
> > + maxItems: 1
> > +
> > + adi,manual-span-operation-config:
> > + description:
> > + This property must mimic the MSPAN pin configurations. By tying the
> MSPAN
> > + pins (MSP2, MSP1 and MSP0) to GND and/or VCC, any output range can
> be
> > + hardware-configured with different mid-scale or zero-scale reset options.
> > + The hardware configuration is latched during power on reset for proper
> > + operation.
> > + 0 - MPS2=GND, MPS1=GND, MSP0=GND (+-10V, reset to 0V)
> > + 1 - MPS2=GND, MPS1=GND, MSP0=VCC (+-5V, reset to 0V)
> > + 2 - MPS2=GND, MPS1=VCC, MSP0=GND (+-2.5V, reset to 0V)
> > + 3 - MPS2=GND, MPS1=VCC, MSP0=VCC (0V to 10, reset to 0V)
> > + 4 - MPS2=VCC, MPS1=GND, MSP0=GND (0V to 10V, reset to 5V)
> > + 5 - MPS2=VCC, MPS1=GND, MSP0=VCC (0V to 5V, reset to 0V)
> > + 6 - MPS2=VCC, MPS1=VCC, MSP0=GND (0V to 5V, reset to 2.5V)
> > + 7 - MPS2=VCC, MPS1=VCC, MSP0=VCC (0V to 5V, reset to 0V, enables
> SoftSpan)
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + enum: [0, 1, 2, 3, 4, 5, 6, 7]
>
> Can you explain why this property is required, when below there's one that sets
> the ranges in microvolts? Isn't the only new information that this provides the
> reset values (in a few cases that it is not 0).
> What am I missing?

For specifying output range and reset options without relying on software initialization
routines, and also for enabling the softspan feature, I think this property seems essential.

> > + default: 7
> > +
> > + io-channels:
> > + description:
> > + ADC channel to monitor voltages and temperature at the MUXOUT pin.
> > + maxItems: 1
> > +
> > + '#address-cells':
> > + const: 1
> > +
> > + '#size-cells':
> > + const: 0
> > +
> > +patternProperties:
> > + "^channel@[0-3]$":
> > + type: object
> > + additionalProperties: false
> > +
> > + properties:
> > + reg:
> > + description: The channel number representing the DAC output channel.
> > + maximum: 3
> > +
> > + adi,toggle-mode:
> > + description:
> > + Set the channel as a toggle enabled channel. Toggle operation enables
> > + fast switching of a DAC output between two different DAC codes
> without
> > + any SPI transaction.
> > + type: boolean
> > +
> > + adi,output-range-microvolt:
> > + description: Specify the channel output full scale range.
> > + oneOf:
> > + - items:
> > + - const: 0
> > + - enum: [5000000, 10000000]
> > + - items:
> > + - const: -5000000
> > + - const: 5000000
> > + - items:
> > + - const: -10000000
> > + - const: 10000000
> > + - items:
> > + - const: -2500000
> > + - const: 2500000
> > +
> > + required:
> > + - reg
> > + - adi,output-range-microvolt
> > +
> > +required:
> > + - compatible
> > + - reg
> > + - spi-max-frequency
> > + - vcc-supply
> > + - iovcc-supply
> > + - v-pos-supply
> > + - v-neg-supply
> > +
> > +allOf:
> > + - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + spi {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > + dac@0 {
> > + compatible = "adi,ltc2664";
> > + reg = <0>;
> > + spi-max-frequency = <10000000>;
> > +
> > + vcc-supply = <&vcc>;
> > + iovcc-supply = <&vcc>;
> > + ref-supply = <&vref>;
> > + v-pos-supply = <&vpos>;
> > + v-neg-supply = <&vneg>;
> > +
> > + io-channels = <&adc 0>;
> > +
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > + channel@0 {
> > + reg = <0>;
> > + adi,toggle-mode;
> > + adi,output-range-microvolt = <(-10000000) 10000000>;
> > + };
> > +
> > + channel@1 {
> > + reg = <1>;
> > + adi,output-range-microvolt = <0 10000000>;
> > + };
> > + };
> > + };
> > +...
> > diff --git a/MAINTAINERS b/MAINTAINERS index
> > be590c462d91..849800d9cbf7 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -13074,6 +13074,14 @@ S: Maintained
> > F: Documentation/devicetree/bindings/iio/dac/lltc,ltc1660.yaml
> > F: drivers/iio/dac/ltc1660.c
> >
> > +LTC2664 IIO DAC DRIVER
> > +M: Michael Hennerich <michael.hennerich@analog.com>
> > +M: Kim Seer Paller <kimseer.paller@analog.com>
> > +L: linux-iio@vger.kernel.org
> > +S: Supported
> > +W: https://ez.analog.com/linux-software-drivers
> > +F: Documentation/devicetree/bindings/iio/dac/adi,ltc2664.yaml
> > +
> > LTC2688 IIO DAC DRIVER
> > M: Nuno Sá <nuno.sa@analog.com>
> > L: linux-iio@vger.kernel.org
> > --
> > 2.34.1
> >