Re: [PATCH 1/3] dt-bindings: iio: adc: add support for AD5940

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 14 Nov 2019 21:32:06 +0800
Song Qiang <songqiang1304521@gmail.com> wrote:

> On 11/11/19 12:26 AM, Jonathan Cameron wrote:
> > On Fri,  8 Nov 2019 21:09:44 +0800
> > Song Qiang <songqiang1304521@gmail.com> wrote:
> >   
> >> Add yaml devicetree description file and a header file for
> >> helping configure positive and negtive input of AD5940.
> >>
> >> Signed-off-by: Song Qiang <songqiang1304521@gmail.com>  
> > Ouch. This is a very complex device, so I'm guessing this is the tip
> > of the iceberg when it comes to the eventual binding.
> > For reference of others this has a similarly complex DAC and
> > TIA + some excitation voltage generators (DDS).
> > 
> > Anyhow, a few comments inline but I'll definitely be looking for
> > a dt maintainer input on this one.
> > 
> > Thanks,
> > 
> > Jonathan
> >   
> 
> Thanks, this is the first part support of the driver.
> 
> >> ---
> >>  .../bindings/iio/adc/adi,ad5940.yaml          | 240 ++++++++++++++++++
> >>  include/dt-bindings/iio/adc/adi,ad5940.h      |  52 ++++
> >>  2 files changed, 292 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad5940.yaml
> >>  create mode 100644 include/dt-bindings/iio/adc/adi,ad5940.h
> >>
> >> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad5940.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad5940.yaml
> >> new file mode 100644
> >> index 000000000000..f7f034fdd8ec
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad5940.yaml
> >> @@ -0,0 +1,240 @@
> >> +# SPDX-License-Identifier: GPL-2.0  
> > For new bindings, preference is to include a dual license
> > (GPL-2.0-only OR BSD-2-Clause)
> > 
> > If Analog is fine doing this that would be great.
> >   
> 
> I'll consult my mentor about this.
> 
> >> +# Copyright 2019 Analog Devices Inc.
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/bindings/iio/adc/adi,ad5940.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Analog Devices AD5940 Device Tree Bindings
> >> +
> >> +maintainers:
> >> +  - Song Qiang <songqiang1304521@gmail.com>
> >> +
> >> +description: |
> >> +  Analog Devices AD5940 High Precision, Impedance, and Electrochemical Front End.
> >> +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD5940.pdf
> >> +
> >> +properties:
> >> +  compatible:
> >> +    enum:
> >> +      - adi,ad5940
> >> +
> >> +  reg:
> >> +    maxItems: 1
> >> +
> >> +  vref-supply:
> >> +    description:
> >> +      The regulator to be used to supply the reference voltage.
> >> +    maxItems: 1  
> > 
> > It's worth taking a look at similar patch reviews to pick up on things
> > that are common issues.  Rob has pointed out a few times recently that
> > vref-supply can only ever have one item, so no need for maxItems.
> >   
> 
> That's right, thanks.
> 
> >> +
> >> +  adi,interrupt-io:
> >> +    description:
> >> +      Output GPIO index of interrupt controller of AD5940.
> >> +    maxItems: 1  
> > 
> > I'm fairly sure an enum can only have one entry so don't think this is
> > needed.
> >   
> >> +    allOf:
> >> +      - $ref: /schemas/types.yaml#/definitions/uint32
> >> +      - enum: [0, 3, 6, 7]
> >> +
> >> +  '#address-cells':
> >> +    const: 1
> >> +
> >> +  '#size-cells':
> >> +    const: 0
> >> +
> >> +required:
> >> +  - compatible
> >> +  - reg
> >> +  - interrupts
> >> +  - adi,interrupt-io
> >> +
> >> +patternProperties:
> >> +  # 'channel@0-255'  
> > 
> > Really?  That is a lot of channels.  Superficially it looks like a much
> > smaller number of possibilities from the datasheet.
> >   
> 
> This device has some positive inputs and some negative inputs. A channel
> here is a combination of one positive input and one negative input.
> These channels I listed in examples are only suggested combinations in
> the datasheet, while other combinations are all possible. So I was
> thinking to not limit the total count of channels here. I failed to find
> examples of doing this kind of stuff in the tree.

As we are putting the controls for these in DT, we are making the claim
that they are inherently part of the 'hardware'.   The fully flexibility
probably doesn't make sense even if the hardware supports it.

I'd be tempted to just not specify a limit at all, but rely on the type
of 'reg' to provide an ultimate limit.  That gets rid of a lot
of the complexity in the binding.

Reality is that for a device like this you aren't going to have more
channels than postive inputs because the vast majority of the time
there is little reason to measure a given input against multiple
references.

Thanks,

Jonathan
> 
> yours,
> Song Qiang
> 
> >> +  "^channel@([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$":
> >> +    type: object
> >> +    description: |
> >> +      Represents the external channels which are connected to the ADC.
> >> +      See Documentation/devicetree/bindings/iio/adc/adc.txt.
> >> +    properties:
> >> +      reg:
> >> +        description:
> >> +          Index of this channel, must be starting from 0.
> >> +        maxItems: 1
> >> +
> >> +      diff-channels:
> >> +        description:
> >> +          Positive input and negtive input of the ADC buffer of this channel.
> >> +          Input candidates are defined in include/dt-bindings/iio/adc/adi,ad5940.h.
> >> +        minItems: 2
> >> +        maxItems: 2
> >> +        items:
> >> +          - description: Positive input channel
> >> +          - enum:
> >> +            - AD5940_ADC_INPUTP_EXCITATION
> >> +            - AD5940_ADC_INPUTP_FLOATING
> >> +            - AD5940_ADC_INPUTP_HSTIA
> >> +            - AD5940_ADC_INPUTP_LPTIA_LP
> >> +            - AD5940_ADC_INPUTP_AIN0
> >> +            - AD5940_ADC_INPUTP_AIN1
> >> +            - AD5940_ADC_INPUTP_AIN2
> >> +            - AD5940_ADC_INPUTP_AIN3
> >> +            - AD5940_ADC_INPUTP_AVDD_2
> >> +            - AD5940_ADC_INPUTP_DVDD_2
> >> +            - AD5940_ADC_INPUTP_AVDD_REG_2
> >> +            - AD5940_ADC_INPUTP_TEMP
> >> +            - AD5940_ADC_INPUTP_VBIAS_CAP
> >> +            - AD5940_ADC_INPUTP_DE0
> >> +            - AD5940_ADC_INPUTP_SE0
> >> +            - AD5940_ADC_INPUTP_VREF_2V5_2
> >> +            - AD5940_ADC_INPUTP_VREF_1V82
> >> +            - AD5940_ADC_INPUTP_P_TEMP_N
> >> +            - AD5940_ADC_INPUTP_AIN4
> >> +            - AD5940_ADC_INPUTP_AIN6
> >> +            - AD5940_ADC_INPUTP_VZERO
> >> +            - AD5940_ADC_INPUTP_VBIAS0
> >> +            - AD5940_ADC_INPUTP_VCE0
> >> +            - AD5940_ADC_INPUTP_VRE0
> >> +            - AD5940_ADC_INPUTP_VCE0_2
> >> +            - AD5940_ADC_INPUTP_LPTIA
> >> +            - AD5940_ADC_INPUTP_AGND_REF
> >> +
> >> +          - description: Negtive input channel
> >> +          - enum:
> >> +              # Negtive input candidates
> >> +              - AD5940_ADC_INPUTN_FLOATING
> >> +              - AD5940_ADC_INPUTN_HSTIA
> >> +              - AD5940_ADC_INPUTN_LPTIA
> >> +              - AD5940_ADC_INPUTN_AIN0
> >> +              - AD5940_ADC_INPUTN_AIN1
> >> +              - AD5940_ADC_INPUTN_AIN2
> >> +              - AD5940_ADC_INPUTN_AIN3
> >> +              - AD5940_ADC_INPUTN_VBIAS_CA8
> >> +              - AD5940_ADC_INPUTN_TEMP_N
> >> +              - AD5940_ADC_INPUTN_AIN4
> >> +              - AD5940_ADC_INPUTN_AIN6
> >> +              - AD5940_ADC_INPUTN_VZERO
> >> +              - AD5940_ADC_INPUTN_VBIAS0
> >> +              - AD5940_ADC_INPUTN_EXCITATION
> >> +
> >> +      channel-name:
> >> +        description:
> >> +          Any string format name you would like to assign to this channel.
> >> +        maxItems: 1
> >> +
> >> +    required:
> >> +      - reg
> >> +      - diff-channels
> >> +      - channel-name
> >> +
> >> +examples:
> >> +  - |
> >> +    ad5940: ad5940@0 {
> >> +      compatible = "adi,ad5940";
> >> +      reg = <0>;
> >> +      spi-max-frequency = <16000000>;
> >> +      vref-supply = <&adc_vref>;
> >> +      interrupt-parent = <&gpio>;
> >> +      interrupts = <24 2>;
> >> +
> >> +      adi,interrupt-io = <0>;
> >> +
> >> +      #address-cells = <1>;
> >> +      #size-cells = <0>;
> >> +
> >> +      channel@0 {
> >> +        reg = <0>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_VCE0
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "Vce-Vbias";
> >> +      };
> >> +
> >> +      channel@1 {
> >> +        reg = <1>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_VRE0
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "Vre-Vbias";
> >> +      };
> >> +
> >> +      channel@2 {
> >> +        reg = <2>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_SE0
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "Vse-Vbias";
> >> +      };
> >> +
> >> +      channel@3 {
> >> +        reg = <3>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_DE0
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "Vde-Vbias";
> >> +      };
> >> +
> >> +      channel@4 {
> >> +        reg = <4>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_AIN0
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "ain0-Vbias";
> >> +      };
> >> +
> >> +      channel@5 {
> >> +        reg = <5>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_AIN1
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "ain1-Vbias";
> >> +      };
> >> +
> >> +      channel@6 {
> >> +        reg = <6>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_AIN2
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "ain2-Vbias";
> >> +      };
> >> +
> >> +      channel@7 {
> >> +        reg = <7>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_AIN3
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "ain3-Vbias";
> >> +      };
> >> +
> >> +      channel@8 {
> >> +        reg = <8>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_AIN4
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "ain4-Vbias";
> >> +      };
> >> +
> >> +      channel@9 {
> >> +        reg = <9>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_AIN6
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "ain6-Vbias";
> >> +      };
> >> +
> >> +      channel@10 {
> >> +        reg = <10>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_LPTIA_LP
> >> +                         AD5940_ADC_INPUTN_LPTIA>;
> >> +        channel-name = "Low power TIA DC";
> >> +      };
> >> +
> >> +      channel@11 {
> >> +        reg = <11>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_LPTIA
> >> +                         AD5940_ADC_INPUTN_LPTIA>;
> >> +        channel-name = "Low power TIA AC";
> >> +      };
> >> +
> >> +      channel@12 {
> >> +        reg = <12>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_HSTIA
> >> +                         AD5940_ADC_INPUTN_HSTIA>;
> >> +        channel-name = "High Speed TIA";
> >> +      };
> >> +
> >> +      channel@13 {
> >> +        reg = <13>;
> >> +        diff-channels = <AD5940_ADC_INPUTP_TEMP
> >> +                         AD5940_ADC_INPUTN_VBIAS0>;
> >> +        channel-name = "Temperature";
> >> +      };
> >> +    };
> >> diff --git a/include/dt-bindings/iio/adc/adi,ad5940.h b/include/dt-bindings/iio/adc/adi,ad5940.h
> >> new file mode 100644
> >> index 000000000000..c17826f2f654
> >> --- /dev/null
> >> +++ b/include/dt-bindings/iio/adc/adi,ad5940.h
> >> @@ -0,0 +1,52 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * This header provides constants for configuring the AD5940 AFE
> >> + */
> >> +
> >> +#ifndef _DT_BINDINGS_IIO_ADC_AD5940_H
> >> +#define _DT_BINDINGS_IIO_ADC_AD5940_H
> >> +
> >> +#define AD5940_ADC_INPUTN_FLOATING	0
> >> +#define AD5940_ADC_INPUTN_HSTIA		1
> >> +#define AD5940_ADC_INPUTN_LPTIA		2
> >> +#define AD5940_ADC_INPUTN_AIN0		4
> >> +#define AD5940_ADC_INPUTN_AIN1		5
> >> +#define AD5940_ADC_INPUTN_AIN2		6
> >> +#define AD5940_ADC_INPUTN_AIN3		7
> >> +#define AD5940_ADC_INPUTN_VBIAS_CA8	10
> >> +#define AD5940_ADC_INPUTN_TEMP_N	11
> >> +#define AD5940_ADC_INPUTN_AIN4		12
> >> +#define AD5940_ADC_INPUTN_AIN6		14
> >> +#define AD5940_ADC_INPUTN_VZERO		16
> >> +#define AD5940_ADC_INPUTN_VBIAS0	17
> >> +#define AD5940_ADC_INPUTN_EXCITATION	20
> >> +
> >> +#define AD5940_ADC_INPUTP_FLOATING	0
> >> +#define AD5940_ADC_INPUTP_HSTIA		1
> >> +#define AD5940_ADC_INPUTP_LPTIA_LP	2
> >> +#define AD5940_ADC_INPUTP_AIN0		4
> >> +#define AD5940_ADC_INPUTP_AIN1		5
> >> +#define AD5940_ADC_INPUTP_AIN2		6
> >> +#define AD5940_ADC_INPUTP_AIN3		7
> >> +#define AD5940_ADC_INPUTP_AVDD_2	8
> >> +#define AD5940_ADC_INPUTP_DVDD_2	9
> >> +#define AD5940_ADC_INPUTP_AVDD_REG_2	10
> >> +#define AD5940_ADC_INPUTP_TEMP		11
> >> +#define AD5940_ADC_INPUTP_VBIAS_CAP	12
> >> +#define AD5940_ADC_INPUTP_DE0		13
> >> +#define AD5940_ADC_INPUTP_SE0		14
> >> +#define AD5940_ADC_INPUTP_VREF_2V5_2	16
> >> +#define AD5940_ADC_INPUTP_VREF_1V82	18
> >> +#define AD5940_ADC_INPUTP_P_TEMP_N	19
> >> +#define AD5940_ADC_INPUTP_AIN4		20
> >> +#define AD5940_ADC_INPUTP_AIN6		22
> >> +#define AD5940_ADC_INPUTP_VZERO		23
> >> +#define AD5940_ADC_INPUTP_VBIAS0	24
> >> +#define AD5940_ADC_INPUTP_VCE0		25
> >> +#define AD5940_ADC_INPUTP_VRE0		26
> >> +#define AD5940_ADC_INPUTP_VCE0_2	31
> >> +#define AD5940_ADC_INPUTP_LPTIA		33
> >> +#define AD5940_ADC_INPUTP_AGND_REF	35
> >> +#define AD5940_ADC_INPUTP_EXCITATION	36
> >> +
> >> +#endif /* _DT_BINDINGS_IIO_ADC_AD5940 */  
> >