Re: [PATCH 20/29] dt-bindings:iio:dac:microchip,mcp4725 yaml conversion

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 12 Oct 2020 16:02:30 +0200
Tomas Novotny <tomas@novotny.cz> wrote:

> Hi Jonathan,
> 
> On Sun, 11 Oct 2020 18:07:40 +0100
> Jonathan Cameron <jic23@kernel.org> wrote:
> 
> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > 
> > I'm not sure vdd-supply absolutely has to be provided if vref-supply
> > is, but as the previous binding docs stated it was required it seems
> > reasonable to leave it as such.  
> 
> Good catch. Vdd is useless on MCP4726 if Vref is specified. The driver
> requires Vdd...

The driver will get the regulator but as it's not via an optional
call it the regulator core will provide a stub regulator.
If the ref regulator is present, all that will happen with vdd is
a regulator_enable() call which is fine with a stub regulator (it's
a noop).   So we should be good to update the binding to specify
the requirement.   Perhaps it's one to do as a follow up patch?
Given any existing DT must be providing that regulator, there is
no rush for us to fix it :)

> 
> How to proceed there?
> 
> Thanks,
> 
> Tomas
> 
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Cc:  Tomas Novotny <tomas@novotny.cz>
> > ---
> >  .../devicetree/bindings/iio/dac/mcp4725.txt   | 35 ---------
> >  .../bindings/iio/dac/microchip,mcp4725.yaml   | 71 +++++++++++++++++++
> >  2 files changed, 71 insertions(+), 35 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/dac/mcp4725.txt b/Documentation/devicetree/bindings/iio/dac/mcp4725.txt
> > deleted file mode 100644
> > index 1bc6c093fbfe..000000000000
> > --- a/Documentation/devicetree/bindings/iio/dac/mcp4725.txt
> > +++ /dev/null
> > @@ -1,35 +0,0 @@
> > -Microchip mcp4725 and mcp4726 DAC device driver
> > -
> > -Required properties:
> > -	- compatible: Must be "microchip,mcp4725" or "microchip,mcp4726"
> > -	- reg: Should contain the DAC I2C address
> > -	- vdd-supply: Phandle to the Vdd power supply. This supply is used as a
> > -	  voltage reference on mcp4725. It is used as a voltage reference on
> > -	  mcp4726 if there is no vref-supply specified.
> > -
> > -Optional properties (valid only for mcp4726):
> > -	- vref-supply: Optional phandle to the Vref power supply. Vref pin is
> > -	  used as a voltage reference when this supply is specified.
> > -	- microchip,vref-buffered: Boolean to enable buffering of the external
> > -	  Vref pin. This boolean is not valid without the vref-supply. Quoting
> > -	  the datasheet: This is offered in cases where the reference voltage
> > -	  does not have the current capability not to drop its voltage when
> > -	  connected to the internal resistor ladder circuit.
> > -
> > -Examples:
> > -
> > -	/* simple mcp4725 */
> > -	mcp4725@60 {
> > -		compatible = "microchip,mcp4725";
> > -		reg = <0x60>;
> > -		vdd-supply = <&vdac_vdd>;
> > -	};
> > -
> > -	/* mcp4726 with the buffered external reference voltage */
> > -	mcp4726@60 {
> > -		compatible = "microchip,mcp4726";
> > -		reg = <0x60>;
> > -		vdd-supply = <&vdac_vdd>;
> > -		vref-supply = <&vdac_vref>;
> > -		microchip,vref-buffered;
> > -	};
> > diff --git a/Documentation/devicetree/bindings/iio/dac/microchip,mcp4725.yaml b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4725.yaml
> > new file mode 100644
> > index 000000000000..271998610ceb
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/dac/microchip,mcp4725.yaml
> > @@ -0,0 +1,71 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/dac/microchip,mcp4725.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Microchip mcp4725 and mcp4726 DAC
> > +
> > +maintainers:
> > +  - Tomas Novotny <tomas@novotny.cz>
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - microchip,mcp4725
> > +      - microchip,mcp4726
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  vdd-supply:
> > +    description: |
> > +      Provides both power and acts as the reference supply on the mcp4725.
> > +      For the mcp4726 it will be used as the reference voltage if vref-supply
> > +      is not provided.
> > +
> > +  vref-supply:
> > +    description:
> > +      Vref pin is used as a voltage reference when this supply is specified.
> > +
> > +  microchip,vref-buffered:
> > +    type: boolean
> > +    description: |
> > +      Enable buffering of the external Vref pin. This boolean is not valid
> > +      without the vref-supply. Quoting the datasheet: This is offered in
> > +      cases where the reference voltage does not have the current
> > +      capability not to drop its voltage when connected to the internal
> > +      resistor ladder circuit.
> > +
> > +allOf:
> > +  - if:
> > +      not:
> > +        properties:
> > +          compatible:
> > +            contains:
> > +              const: microchip,mcp4726
> > +    then:
> > +      properties:
> > +        vref-supply: false
> > +        microchip,vref-buffered: false
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - vdd-supply
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    i2c {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        mcp4725@60 {
> > +            compatible = "microchip,mcp4725";
> > +            reg = <0x60>;
> > +            vdd-supply = <&vdac_vdd>;
> > +        };
> > +    };
> > +...