Add adi,sync-in-spi property to enable synchronization over SPI.
This should be used in the case when the GPIO cannot provide a
pulse synchronous with the base MCLK signal.

User can choose between SPI, GPIO synchronization or neither of them,
but only if a external pulse can be provided, for example, by another
device in a multidevice setup.

Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
---
 .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
index 3ce59d4d065f..55cec27bfe60 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
@@ -47,6 +47,15 @@ properties:
       in any way, for example if the filter decimation rate changes.
       As the line is active low, it should be marked GPIO_ACTIVE_LOW.
 
+  adi,sync-in-spi:
+    description:
+      Enables synchronization of multiple devices over SPI. This property is
+      used when a signal synchronous to the base MCLK signal cannot be provided
+      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
+      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
+      should be routed to the SYNC_IN pins of the other devices.
+    type: boolean
+
   reset-gpios:
     maxItems: 1
 
@@ -65,7 +74,6 @@ required:
   - vref-supply
   - spi-cpol
   - spi-cpha
-  - adi,sync-in-gpios
 
 patternProperties:
   "^channel@([0-9]|1[0-5])$":
@@ -89,6 +97,20 @@ patternProperties:
 allOf:
   - $ref: /schemas/spi/spi-peripheral-props.yaml#
 
+  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
+  - if:
+      required:
+        - adi,sync-in-gpios
+    then:
+      properties:
+        adi,sync-in-spi: false
+  - if:
+      required:
+        - adi,sync-in-spi
+    then:
+      properties:
+        adi,sync-in-gpios: false
+
 unevaluatedProperties: false
 
 examples:
-- 
2.34.1

On 01/07, Jonathan Santos wrote:
> Add adi,sync-in-spi property to enable synchronization over SPI.
> This should be used in the case when the GPIO cannot provide a
> pulse synchronous with the base MCLK signal.
> 
> User can choose between SPI, GPIO synchronization or neither of them,
> but only if a external pulse can be provided, for example, by another
> device in a multidevice setup.
> 
> Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> ---
>  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> index 3ce59d4d065f..55cec27bfe60 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> @@ -47,6 +47,15 @@ properties:
>        in any way, for example if the filter decimation rate changes.
>        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
>  
> +  adi,sync-in-spi:
> +    description:
> +      Enables synchronization of multiple devices over SPI. This property is
> +      used when a signal synchronous to the base MCLK signal cannot be provided
> +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> +      should be routed to the SYNC_IN pins of the other devices.
So, if I'm getting it right, /SYNC_IN may be driven by a GPIO (ADAQ7768-1
datasheet Figure 131), /SYNC_IN may be driven by own device /SYNC_OUT
(ADAQ7768-1 datasheet Figure 133), or /SYNC_IN may be driven by other AD7768-1
/SYNC_OUT pin (also Figure 133).
That is too much to describe with a boolean.

If David's suggestion of using a trigger-source doesn't fit, this property
should at least become an enum or string.

> +    type: boolean
> +
>    reset-gpios:
>      maxItems: 1
>  
> @@ -65,7 +74,6 @@ required:
>    - vref-supply
>    - spi-cpol
>    - spi-cpha
> -  - adi,sync-in-gpios
>  
>  patternProperties:
>    "^channel@([0-9]|1[0-5])$":
> @@ -89,6 +97,20 @@ patternProperties:
>  allOf:
>    - $ref: /schemas/spi/spi-peripheral-props.yaml#
>  
> +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> +  - if:
> +      required:
> +        - adi,sync-in-gpios
> +    then:
> +      properties:
> +        adi,sync-in-spi: false
> +  - if:
> +      required:
> +        - adi,sync-in-spi
> +    then:
> +      properties:
> +        adi,sync-in-gpios: false
> +
>  unevaluatedProperties: false
>  
>  examples:
> -- 
> 2.34.1
>

On Fri, 10 Jan 2025 18:51:06 -0300
Marcelo Schmitt <marcelo.schmitt1@gmail.com> wrote:

> On 01/07, Jonathan Santos wrote:
> > Add adi,sync-in-spi property to enable synchronization over SPI.
> > This should be used in the case when the GPIO cannot provide a
> > pulse synchronous with the base MCLK signal.
> > 
> > User can choose between SPI, GPIO synchronization or neither of them,
> > but only if a external pulse can be provided, for example, by another
> > device in a multidevice setup.
> > 
> > Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > ---
> >  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
> >  1 file changed, 23 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > index 3ce59d4d065f..55cec27bfe60 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > @@ -47,6 +47,15 @@ properties:
> >        in any way, for example if the filter decimation rate changes.
> >        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
> >  
> > +  adi,sync-in-spi:
> > +    description:
> > +      Enables synchronization of multiple devices over SPI. This property is
> > +      used when a signal synchronous to the base MCLK signal cannot be provided
> > +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> > +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> > +      should be routed to the SYNC_IN pins of the other devices.  
> So, if I'm getting it right,

Datasheet on this is indeed complex!

>/SYNC_IN may be driven by a GPIO (ADAQ7768-1 datasheet Figure 131),

For that we expose a gpio binding already. If that's present we know what is going on.

>/SYNC_IN may be driven by own device /SYNC_OUT (ADAQ7768-1 datasheet Figure 133),

This is the default - no information provided so it isn't wired externally.
We don't normally bother to describe required chip to chip connections.
I couldn't entirely figure out if this is 'required' if we aren't driving explicitly
from GPIO or another chip but i think it is(?).

>/SYNC_IN may be driven by other AD7768-1 > /SYNC_OUT pin (also Figure 133).
This is only case we are about for sync in I think.

As long as there isn't a valid 'not connected' It think we are fine with a boolean.

> That is too much to describe with a boolean.
> 
> If David's suggestion of using a trigger-source doesn't fit, this property
> should at least become an enum or string.
> 
> > +    type: boolean
> > +
> >    reset-gpios:
> >      maxItems: 1
> >  
> > @@ -65,7 +74,6 @@ required:
> >    - vref-supply
> >    - spi-cpol
> >    - spi-cpha
> > -  - adi,sync-in-gpios
> >  
> >  patternProperties:
> >    "^channel@([0-9]|1[0-5])$":
> > @@ -89,6 +97,20 @@ patternProperties:
> >  allOf:
> >    - $ref: /schemas/spi/spi-peripheral-props.yaml#
> >  
> > +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> > +  - if:
> > +      required:
> > +        - adi,sync-in-gpios
> > +    then:
> > +      properties:
> > +        adi,sync-in-spi: false
> > +  - if:
> > +      required:
> > +        - adi,sync-in-spi
> > +    then:
> > +      properties:
> > +        adi,sync-in-gpios: false
> > +
> >  unevaluatedProperties: false
> >  
> >  examples:
> > -- 
> > 2.34.1
> >

On 01/12, Jonathan Cameron wrote:
> On Fri, 10 Jan 2025 18:51:06 -0300
> Marcelo Schmitt <marcelo.schmitt1@gmail.com> wrote:
> 
> > On 01/07, Jonathan Santos wrote:
> > > Add adi,sync-in-spi property to enable synchronization over SPI.
> > > This should be used in the case when the GPIO cannot provide a
> > > pulse synchronous with the base MCLK signal.
> > > 
> > > User can choose between SPI, GPIO synchronization or neither of them,
> > > but only if a external pulse can be provided, for example, by another
> > > device in a multidevice setup.
> > > 
> > > Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > > ---
> > >  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
> > >  1 file changed, 23 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > index 3ce59d4d065f..55cec27bfe60 100644
> > > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > @@ -47,6 +47,15 @@ properties:
> > >        in any way, for example if the filter decimation rate changes.
> > >        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
> > >  
> > > +  adi,sync-in-spi:
> > > +    description:
> > > +      Enables synchronization of multiple devices over SPI. This property is
> > > +      used when a signal synchronous to the base MCLK signal cannot be provided
> > > +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> > > +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> > > +      should be routed to the SYNC_IN pins of the other devices.  
> > So, if I'm getting it right,
> 
> Datasheet on this is indeed complex!
> 
> >/SYNC_IN may be driven by a GPIO (ADAQ7768-1 datasheet Figure 131),
> 
> For that we expose a gpio binding already. If that's present we know what is going on.
> 
> >/SYNC_IN may be driven by own device /SYNC_OUT (ADAQ7768-1 datasheet Figure 133),
> 
> This is the default - no information provided so it isn't wired externally.
> We don't normally bother to describe required chip to chip connections.
> I couldn't entirely figure out if this is 'required' if we aren't driving explicitly
> from GPIO or another chip but i think it is(?).
>

It is. If the device is not being driven by a GPIO or an external
device, the user should connect the /SYNC_OUT to /SYNC_IN. We could
assume that this is the case if the GPIO is not present in the
devicetree, maybe put that into the description. The sync-out-sync-in
property as a boolean can be quite redundant, since we also need to
remove the GPIO.

> >/SYNC_IN may be driven by other AD7768-1 > /SYNC_OUT pin (also Figure 133).
> This is only case we are about for sync in I think.
> 
> As long as there isn't a valid 'not connected' It think we are fine with a boolean.
> 

If opt for a single node instace, thats ok; otherwise, David's
trigger-sources suggestion seems to be the best approach. 

> > That is too much to describe with a boolean.
> > 
> > If David's suggestion of using a trigger-source doesn't fit, this property
> > should at least become an enum or string.
> > 
> > > +    type: boolean
> > > +
> > >    reset-gpios:
> > >      maxItems: 1
> > >  
> > > @@ -65,7 +74,6 @@ required:
> > >    - vref-supply
> > >    - spi-cpol
> > >    - spi-cpha
> > > -  - adi,sync-in-gpios
> > >  
> > >  patternProperties:
> > >    "^channel@([0-9]|1[0-5])$":
> > > @@ -89,6 +97,20 @@ patternProperties:
> > >  allOf:
> > >    - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > >  
> > > +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> > > +  - if:
> > > +      required:
> > > +        - adi,sync-in-gpios
> > > +    then:
> > > +      properties:
> > > +        adi,sync-in-spi: false
> > > +  - if:
> > > +      required:
> > > +        - adi,sync-in-spi
> > > +    then:
> > > +      properties:
> > > +        adi,sync-in-gpios: false
> > > +
> > >  unevaluatedProperties: false
> > >  
> > >  examples:
> > > -- 
> > > 2.34.1
> > >   
>

On 1/7/25 9:24 AM, Jonathan Santos wrote:
> Add adi,sync-in-spi property to enable synchronization over SPI.
> This should be used in the case when the GPIO cannot provide a
> pulse synchronous with the base MCLK signal.
> 
> User can choose between SPI, GPIO synchronization or neither of them,
> but only if a external pulse can be provided, for example, by another
> device in a multidevice setup.
> 

While we are fixing up these bindings, we could add some more trivial things,
like power supplies.

Also, the interrupt property could use a description since the chip has multiple
output pins. I assume it means the /DRDY pin?

> Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> ---
>  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> index 3ce59d4d065f..55cec27bfe60 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> @@ -47,6 +47,15 @@ properties:
>        in any way, for example if the filter decimation rate changes.
>        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
>  
> +  adi,sync-in-spi:

If this is saying that SYNC_OUT is connected to SYNC_IN, then I think the name
should be something like adi,sync-in-sync-out. SPI seems irrelevant here since
we should just be describing how things are wired up, not how it is being used.

But if we also need to consider the case where SYNC_OUT of one chip is connected
to SYNC_IN of another chip, we might want to consider using trigger-source
bindings instead (recently standardized in dtschema).

> +    description:
> +      Enables synchronization of multiple devices over SPI. This property is
> +      used when a signal synchronous to the base MCLK signal cannot be provided
> +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> +      should be routed to the SYNC_IN pins of the other devices.
> +    type: boolean
> +
>    reset-gpios:
>      maxItems: 1
>  
> @@ -65,7 +74,6 @@ required:
>    - vref-supply
>    - spi-cpol
>    - spi-cpha
> -  - adi,sync-in-gpios
>  
>  patternProperties:
>    "^channel@([0-9]|1[0-5])$":
> @@ -89,6 +97,20 @@ patternProperties:
>  allOf:
>    - $ref: /schemas/spi/spi-peripheral-props.yaml#
>  
> +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> +  - if:
> +      required:
> +        - adi,sync-in-gpios
> +    then:
> +      properties:
> +        adi,sync-in-spi: false
> +  - if:
> +      required:
> +        - adi,sync-in-spi
> +    then:
> +      properties:
> +        adi,sync-in-gpios: false

I think this can be simplified to using oneOf: to provide XOR validation

> +
>  unevaluatedProperties: false
>  
>  examples:

On 01/07, David Lechner wrote:
> On 1/7/25 9:24 AM, Jonathan Santos wrote:
> > Add adi,sync-in-spi property to enable synchronization over SPI.
> > This should be used in the case when the GPIO cannot provide a
> > pulse synchronous with the base MCLK signal.
> > 
> > User can choose between SPI, GPIO synchronization or neither of them,
> > but only if a external pulse can be provided, for example, by another
> > device in a multidevice setup.
> > 
> 
> While we are fixing up these bindings, we could add some more trivial things,
> like power supplies.
> 
> Also, the interrupt property could use a description since the chip has multiple
> output pins. I assume it means the /DRDY pin?
> 

Right! Yes, the interrupt pin refers to the /DRDY.

> > Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > ---
> >  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
> >  1 file changed, 23 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > index 3ce59d4d065f..55cec27bfe60 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > @@ -47,6 +47,15 @@ properties:
> >        in any way, for example if the filter decimation rate changes.
> >        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
> >  
> > +  adi,sync-in-spi:
> 
> If this is saying that SYNC_OUT is connected to SYNC_IN, then I think the name
> should be something like adi,sync-in-sync-out. SPI seems irrelevant here since
> we should just be describing how things are wired up, not how it is being used.
> 
> But if we also need to consider the case where SYNC_OUT of one chip is connected
> to SYNC_IN of another chip, we might want to consider using trigger-source
> bindings instead (recently standardized in dtschema).
> 

Do you mean the trigger-sources used for LEDs? I can try to see if it works, but would it
handle the non-GPIO case? While testing a multidevice setup, I found it simpler to 
have a single device to manage everything. It lets us toggle the GPIO or /SYNC_OUT
without referencing another device and makes simultaneous buffered reads easier.

Maybe we could stick to synchronization within the chip for now.

> > +    description:
> > +      Enables synchronization of multiple devices over SPI. This property is
> > +      used when a signal synchronous to the base MCLK signal cannot be provided
> > +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> > +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> > +      should be routed to the SYNC_IN pins of the other devices.
> > +    type: boolean
> > +
> >    reset-gpios:
> >      maxItems: 1
> >  
> > @@ -65,7 +74,6 @@ required:
> >    - vref-supply
> >    - spi-cpol
> >    - spi-cpha
> > -  - adi,sync-in-gpios
> >  
> >  patternProperties:
> >    "^channel@([0-9]|1[0-5])$":
> > @@ -89,6 +97,20 @@ patternProperties:
> >  allOf:
> >    - $ref: /schemas/spi/spi-peripheral-props.yaml#
> >  
> > +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> > +  - if:
> > +      required:
> > +        - adi,sync-in-gpios
> > +    then:
> > +      properties:
> > +        adi,sync-in-spi: false
> > +  - if:
> > +      required:
> > +        - adi,sync-in-spi
> > +    then:
> > +      properties:
> > +        adi,sync-in-gpios: false
> 
> I think this can be simplified to using oneOf: to provide XOR validation
> 

Right!

> > +
> >  unevaluatedProperties: false
> >  
> >  examples:
>

On 1/11/25 4:34 PM, Jonathan Santos wrote:
> On 01/07, David Lechner wrote:
>> On 1/7/25 9:24 AM, Jonathan Santos wrote:
>>> Add adi,sync-in-spi property to enable synchronization over SPI.
>>> This should be used in the case when the GPIO cannot provide a
>>> pulse synchronous with the base MCLK signal.
>>>
>>> User can choose between SPI, GPIO synchronization or neither of them,
>>> but only if a external pulse can be provided, for example, by another
>>> device in a multidevice setup.
>>>
>>
>> While we are fixing up these bindings, we could add some more trivial things,
>> like power supplies.
>>
>> Also, the interrupt property could use a description since the chip has multiple
>> output pins. I assume it means the /DRDY pin?
>>
> 
> Right! Yes, the interrupt pin refers to the /DRDY.
> 
>>> Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
>>> ---
>>>  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
>>>  1 file changed, 23 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
>>> index 3ce59d4d065f..55cec27bfe60 100644
>>> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
>>> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
>>> @@ -47,6 +47,15 @@ properties:
>>>        in any way, for example if the filter decimation rate changes.
>>>        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
>>>  
>>> +  adi,sync-in-spi:
>>
>> If this is saying that SYNC_OUT is connected to SYNC_IN, then I think the name
>> should be something like adi,sync-in-sync-out. SPI seems irrelevant here since
>> we should just be describing how things are wired up, not how it is being used.
>>
>> But if we also need to consider the case where SYNC_OUT of one chip is connected
>> to SYNC_IN of another chip, we might want to consider using trigger-source
>> bindings instead (recently standardized in dtschema).
>>
> 
> Do you mean the trigger-sources used for LEDs?

Sort of. There is a more general version of this binding in dt-schema now [1].
But it is essentially the same binding.

[1]: https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/trigger/trigger-source.yaml

> I can try to see if it works, but would it handle the non-GPIO case?

Since the ADC chip is both a trigger provider and a trigger consumer, it would
actually have both properties. A chip that has SYNC_OUT wired to SYNC_IN would
look something like this:

adc1: adc@0 {
  ...
  properties:
    #trigger-source-cells = <0>;
    trigger-sources = <&adc1>
}

> While testing a multidevice setup, I found it simpler to 
> have a single device to manage everything. It lets us toggle the GPIO or /SYNC_OUT
> without referencing another device and makes simultaneous buffered reads easier.
> 
> Maybe we could stick to synchronization within the chip for now.

In the driver, sure. But for the DT bindings, we want to make sure it makes
sense for future use cases as well since it can't be changed later.

On Sat, 11 Jan 2025 19:34:14 -0300
Jonathan Santos <jonath4nns@gmail.com> wrote:

> On 01/07, David Lechner wrote:
> > On 1/7/25 9:24 AM, Jonathan Santos wrote:  
> > > Add adi,sync-in-spi property to enable synchronization over SPI.
> > > This should be used in the case when the GPIO cannot provide a
> > > pulse synchronous with the base MCLK signal.
> > > 
> > > User can choose between SPI, GPIO synchronization or neither of them,
> > > but only if a external pulse can be provided, for example, by another
> > > device in a multidevice setup.
> > >   
> > 
> > While we are fixing up these bindings, we could add some more trivial things,
> > like power supplies.
> > 
> > Also, the interrupt property could use a description since the chip has multiple
> > output pins. I assume it means the /DRDY pin?
> >   
> 
> Right! Yes, the interrupt pin refers to the /DRDY.
> 
> > > Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > > ---
> > >  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
> > >  1 file changed, 23 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > index 3ce59d4d065f..55cec27bfe60 100644
> > > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > @@ -47,6 +47,15 @@ properties:
> > >        in any way, for example if the filter decimation rate changes.
> > >        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
> > >  
> > > +  adi,sync-in-spi:  
> > 
> > If this is saying that SYNC_OUT is connected to SYNC_IN, then I think the name
> > should be something like adi,sync-in-sync-out. SPI seems irrelevant here since
> > we should just be describing how things are wired up, not how it is being used.
> > 
> > But if we also need to consider the case where SYNC_OUT of one chip is connected
> > to SYNC_IN of another chip, we might want to consider using trigger-source
> > bindings instead (recently standardized in dtschema).
> >   
> 
> Do you mean the trigger-sources used for LEDs? I can try to see if it works, but would it
> handle the non-GPIO case? While testing a multidevice setup, I found it simpler to 
> have a single device to manage everything. It lets us toggle the GPIO or /SYNC_OUT
> without referencing another device and makes simultaneous buffered reads easier.

Daisy-chain mode (figure 131)?  In that case we normally end up with a single presented device
with a 'lot' of channels. (See the electric car style battery charging chips, those can
be chained in very large numbers!)

Probably similar for figure 133 (which is a dual SPI setup) as the SPI clock must
be shared so we still see it over a single interface.

If those are the only two options then keeping this within the driver is fine.
For daisy chain there are examples in tree and it normally means we have to
have a DT parameter that says how long the chain is, though we maybe can
do that with per channel nodes as well if those make sense here.

Jonathan


> 
> Maybe we could stick to synchronization within the chip for now.
> 
> > > +    description:
> > > +      Enables synchronization of multiple devices over SPI. This property is
> > > +      used when a signal synchronous to the base MCLK signal cannot be provided
> > > +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> > > +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> > > +      should be routed to the SYNC_IN pins of the other devices.
> > > +    type: boolean
> > > +
> > >    reset-gpios:
> > >      maxItems: 1
> > >  
> > > @@ -65,7 +74,6 @@ required:
> > >    - vref-supply
> > >    - spi-cpol
> > >    - spi-cpha
> > > -  - adi,sync-in-gpios
> > >  
> > >  patternProperties:
> > >    "^channel@([0-9]|1[0-5])$":
> > > @@ -89,6 +97,20 @@ patternProperties:
> > >  allOf:
> > >    - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > >  
> > > +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> > > +  - if:
> > > +      required:
> > > +        - adi,sync-in-gpios
> > > +    then:
> > > +      properties:
> > > +        adi,sync-in-spi: false
> > > +  - if:
> > > +      required:
> > > +        - adi,sync-in-spi
> > > +    then:
> > > +      properties:
> > > +        adi,sync-in-gpios: false  
> > 
> > I think this can be simplified to using oneOf: to provide XOR validation
> >   
> 
> Right!
> 
> > > +
> > >  unevaluatedProperties: false
> > >  
> > >  examples:  
> >

On 01/12, Jonathan Cameron wrote:
> On Sat, 11 Jan 2025 19:34:14 -0300
> Jonathan Santos <jonath4nns@gmail.com> wrote:
> 
> > On 01/07, David Lechner wrote:
> > > On 1/7/25 9:24 AM, Jonathan Santos wrote:  
> > > > Add adi,sync-in-spi property to enable synchronization over SPI.
> > > > This should be used in the case when the GPIO cannot provide a
> > > > pulse synchronous with the base MCLK signal.
> > > > 
> > > > User can choose between SPI, GPIO synchronization or neither of them,
> > > > but only if a external pulse can be provided, for example, by another
> > > > device in a multidevice setup.
> > > >   
> > > 
> > > While we are fixing up these bindings, we could add some more trivial things,
> > > like power supplies.
> > > 
> > > Also, the interrupt property could use a description since the chip has multiple
> > > output pins. I assume it means the /DRDY pin?
> > >   
> > 
> > Right! Yes, the interrupt pin refers to the /DRDY.
> > 
> > > > Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > > > ---
> > > >  .../bindings/iio/adc/adi,ad7768-1.yaml        | 24 ++++++++++++++++++-
> > > >  1 file changed, 23 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > > index 3ce59d4d065f..55cec27bfe60 100644
> > > > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml
> > > > @@ -47,6 +47,15 @@ properties:
> > > >        in any way, for example if the filter decimation rate changes.
> > > >        As the line is active low, it should be marked GPIO_ACTIVE_LOW.
> > > >  
> > > > +  adi,sync-in-spi:  
> > > 
> > > If this is saying that SYNC_OUT is connected to SYNC_IN, then I think the name
> > > should be something like adi,sync-in-sync-out. SPI seems irrelevant here since
> > > we should just be describing how things are wired up, not how it is being used.
> > > 
> > > But if we also need to consider the case where SYNC_OUT of one chip is connected
> > > to SYNC_IN of another chip, we might want to consider using trigger-source
> > > bindings instead (recently standardized in dtschema).
> > >   
> > 
> > Do you mean the trigger-sources used for LEDs? I can try to see if it works, but would it
> > handle the non-GPIO case? While testing a multidevice setup, I found it simpler to 
> > have a single device to manage everything. It lets us toggle the GPIO or /SYNC_OUT
> > without referencing another device and makes simultaneous buffered reads easier.
> 
> Daisy-chain mode (figure 131)?  In that case we normally end up with a single presented device
> with a 'lot' of channels. (See the electric car style battery charging chips, those can
> be chained in very large numbers!)
>

Actually, it is more like Figure 133 , but the premise is similar. We
have here a Quad setup.

> Probably similar for figure 133 (which is a dual SPI setup) as the SPI clock must
> be shared so we still see it over a single interface.
> 

We could view them as a single device with multiple channels, and since
the goal is to read them simultaneously with buffered reads, some parameters
such as sampling frequency should be equal to all devices.

However, there are some implications: If we do the above, we have
limitations in the customization of the "channels", they would have
the same filter, frequency modulator and scale (we plan to add support
for ADAQ776x-1 series, which include PGA and AAF gain).

To customize them separetely, we would need to assert only the
corresponding chip select, which is only possible with different
instances, as far as I know.

> If those are the only two options then keeping this within the driver is fine.
> For daisy chain there are examples in tree and it normally means we have to
> have a DT parameter that says how long the chain is, though we maybe can
> do that with per channel nodes as well if those make sense here.
> 
> Jonathan
> 

Those are the options in the datasheet and in hardware so far. I was 
considering other scenarios in case the user combine them differently.
I believe keping within the driver covers the main cases. 

> 
> > 
> > Maybe we could stick to synchronization within the chip for now.
> > 
> > > > +    description:
> > > > +      Enables synchronization of multiple devices over SPI. This property is
> > > > +      used when a signal synchronous to the base MCLK signal cannot be provided
> > > > +      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
> > > > +      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
> > > > +      should be routed to the SYNC_IN pins of the other devices.
> > > > +    type: boolean
> > > > +
> > > >    reset-gpios:
> > > >      maxItems: 1
> > > >  
> > > > @@ -65,7 +74,6 @@ required:
> > > >    - vref-supply
> > > >    - spi-cpol
> > > >    - spi-cpha
> > > > -  - adi,sync-in-gpios
> > > >  
> > > >  patternProperties:
> > > >    "^channel@([0-9]|1[0-5])$":
> > > > @@ -89,6 +97,20 @@ patternProperties:
> > > >  allOf:
> > > >    - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > > >  
> > > > +  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
> > > > +  - if:
> > > > +      required:
> > > > +        - adi,sync-in-gpios
> > > > +    then:
> > > > +      properties:
> > > > +        adi,sync-in-spi: false
> > > > +  - if:
> > > > +      required:
> > > > +        - adi,sync-in-spi
> > > > +    then:
> > > > +      properties:
> > > > +        adi,sync-in-gpios: false  
> > > 
> > > I think this can be simplified to using oneOf: to provide XOR validation
> > >   
> > 
> > Right!
> > 
> > > > +
> > > >  unevaluatedProperties: false
> > > >  
> > > >  examples:  
> > >   
>