Re: [PATCH v1 08/13] dt-bindings: iio: adc: adi,ad4134: Document SPI connection mode

[Marcelo Schmitt]

On 09/04, Marcelo Schmitt wrote:
> On 09/03, Conor Dooley wrote:
> > On Wed, Sep 02, 2026 at 02:24:02PM -0300, Marcelo Schmitt wrote:
> > > Document how AD4134 chips are connected to the host SPI controller
> > > according to different wiring configurations.
> > > 
> > > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@xxxxxxxxxx>
> > > ---
> > >  .../bindings/iio/adc/adi,ad4134.yaml          | 22 +++++++++++++++++++
> > >  1 file changed, 22 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> > > index ea6d7e026419..d843c02a394a 100644
> > > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> > > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> > > @@ -131,6 +131,28 @@ properties:
> > >      enum: [ free-running, gated ]
> > >      default: gated
> > >  
> > > +  adi,spi-mode:
> > > +    $ref: /schemas/types.yaml#/definitions/string
> > > +    enum: [ no-cs, 4-wire, one-channel-chain, two-channel-chain ]
> > > +    description: |
> > > +      This property indicates the SPI wiring configuration.
> > > +
> > > +      When this property is omitted, it is assumed that the device is using
> > > +      'no-cs' wiring. When this property is present, it indicates that the
> > > +      device is using one of the following wiring configurations:
> > 
> ...
> > I'd also really appreciate a dts example for a system
> > with one-channel-chain or two-channel-chain looks, given the second
> > device may require different supplies etc. I have no impression in my
> > head of how the dt would be constructed, so I'd like to see wht you have
> > in mind.
> 
...

Realized what I said doesn't make much sense. The peripherals can all have
the same configuration and thus share CS, SCLK, and controller SDO. The wiring
would be like the following

::

  +-----------------------+                               +-----------------+
  |         AD4134        |                               | SPI Controller  |
  |                       |                               |                 |
  |                       |                               |                 |
  | SPI interface    SCLK |<--------------------+---------| SCLK            |
  | for register       CS |<--------------------|-+-------| CS              |
  | access            SDI |<--------------------|-|-+-----| SDO             |
  |                   SDO |------->|¯¯¯¯\       | | |     |                 |
  |                       |        |MUX  >------|-|-|---->| SDI0            |
  | Data interface  DOUT0 |------->|____/<------|-|-|---- | GPIO            |
  | for ADC sample  DOUT1 |---------------------|-|-|---->| SDI1            |
  | data read        DCLK |<-------------+------|-|-|-----| DCLK            |
  |                 DOUT2 |<-+           |      | | |     |                 |
  |                 DOUT3 |<-|-+         |      | | |     |                 |
  |                   ODR |<-|-|---------|--+   | | |  +->| Offload Trigger |
  +-----------------------+  | |         |  |   | | |  |  +-----------------+
                             | |         |  |   | | |  +--| PWM1            |
                             | |         |  +---| | | ----| PWM0            |
                             | |         |  |   | | |    +-----------------+
                             | |         |  |   | | |
  +-----------------------+  | |         |  |   | | |
  |         AD4134        |  | |         |  |   | | |
  |                       |  | |         |  |   | | |
  | SPI interface         |  | |         |  |   | | |
  | for register     SCLK |<-|-|---------|--|---+ | |
  | access             CS |<-|-|---------|--|---|-+ |
  |                   SDI |<-|-|---------|--|---|-|-+
  |                   SDO |  | |         |  |   | | |
  | Data interface        |  | |         |  |   | | |
  | for ADC sample  DOUT0 |--+ |         |  |   | | |
  | data read       DOUT1 |----+         |  |   | | |
  |                 DOUT2 |<-+           |  |   | | |
  |                 DOUT3 |<-|-+         |  |   | | |
  |                  DCLK |<-|-|---------+  |   | | |
  |                   ODR |<-|-|---------|--+   | | |
  +-----------------------+  | |         |  |   | | |
                             | |         |  |   | | |
                             | |         |  |   | | |
                             | |         |  |   | | |
  +-----------------------+  | |         |  |   | | |
  |         AD4134        |  | |         |  |   | | |
  |                       |  | |         |  |   | | |
  |                       |  | |         |  |   | | |
  | SPI interface    SCLK |<-|-|---------|--|---+ | |
  | for register       CS |<-|-|---------|--|-----+ |
  | access            SDI |<-|-|---------|--|-------+
  |                       |  | |         |  |
  | Data interface        |  | |         |  |
  | for ADC sample  DOUT0 |--+ |         |  |
  | data read       DOUT1 |----+         |  |
  |                 DOUT2 |              |  |
  |                 DOUT3 |              |  |
  |                  DCLK |<-------------+  |
  |                   ODR |<----------------+
  +-----------------------+


So we would set them as only one daisy-chained device.

    spi {
        ...
        adc@0 {
            compatible = "adi,ad4134";
            reg = <0>;
            spi-rx-bus-width = <1>, <1>; /* 2 lanes of 1 bit each */

            <supplies, clock, and other properties ...> 

            #daisy-chained-devices = <2>;

            adi,spi-mode = "two-channel-chain";
        };
    };

Thanks,
Marcelo