When SPI offloading is supported, the IIO device provides different sysfs
interfaces to allow using the adjusting the sample rate. Document SPI
offload support for AD4000 and similar devices.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
 Documentation/iio/ad4000.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/iio/ad4000.rst b/Documentation/iio/ad4000.rst
index 468d30dc9214..2d56b0762570 100644
--- a/Documentation/iio/ad4000.rst
+++ b/Documentation/iio/ad4000.rst
@@ -191,3 +191,20 @@ Typical voltage channel attributes of a differential AD4000 series device:
 +-------------------------------------------+------------------------------------------+
 | ``in_voltage0-voltage1_scale_available``  | Toggles input span compression           |
 +-------------------------------------------+------------------------------------------+
+
+SPI offload support
+-------------------
+
+To be able to achieve the maximum sample rate, the driver can be used with the
+`AXI SPI Engine`_ to provide SPI offload support.
+
+.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html
+
+When set for SPI offload support, the IIO device will provide different
+interfaces.
+
+* Either ``in_voltage0_sampling_frequency`` or
+  ``in_voltage0-voltage1_sampling_frequency`` file is provided to allow setting
+  the sample rate.
+* IIO trigger device is not provided (no ``trigger`` directory).
+* ``timestamp`` channel is not provided.
-- 
2.47.2

On Fri, 14 Mar 2025 14:19:33 -0300
Marcelo Schmitt <marcelo.schmitt@analog.com> wrote:

> When SPI offloading is supported, the IIO device provides different sysfs
> interfaces to allow using the adjusting the sample rate. Document SPI
> offload support for AD4000 and similar devices.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> ---
>  Documentation/iio/ad4000.rst | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/Documentation/iio/ad4000.rst b/Documentation/iio/ad4000.rst
> index 468d30dc9214..2d56b0762570 100644
> --- a/Documentation/iio/ad4000.rst
> +++ b/Documentation/iio/ad4000.rst
> @@ -191,3 +191,20 @@ Typical voltage channel attributes of a differential AD4000 series device:
>  +-------------------------------------------+------------------------------------------+
>  | ``in_voltage0-voltage1_scale_available``  | Toggles input span compression           |
>  +-------------------------------------------+------------------------------------------+
> +
> +SPI offload support
> +-------------------
> +
> +To be able to achieve the maximum sample rate, the driver can be used with the
> +`AXI SPI Engine`_ to provide SPI offload support.

Can we make this more generic?  
"the driver can be used with SPI offload engine, such as the ...

I'm rather hoping we see others in the long run as useful little things!
> +
> +.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html
> +
> +When set for SPI offload support, the IIO device will provide different
> +interfaces.
> +
> +* Either ``in_voltage0_sampling_frequency`` or
> +  ``in_voltage0-voltage1_sampling_frequency`` file is provided to allow setting
> +  the sample rate.
> +* IIO trigger device is not provided (no ``trigger`` directory).
> +* ``timestamp`` channel is not provided.

On 03/17, Jonathan Cameron wrote:
> On Fri, 14 Mar 2025 14:19:33 -0300
> Marcelo Schmitt <marcelo.schmitt@analog.com> wrote:
> 
> > When SPI offloading is supported, the IIO device provides different sysfs
> > interfaces to allow using the adjusting the sample rate. Document SPI
> > offload support for AD4000 and similar devices.
> > 
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> > ---
> >  Documentation/iio/ad4000.rst | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> > 
> > diff --git a/Documentation/iio/ad4000.rst b/Documentation/iio/ad4000.rst
> > index 468d30dc9214..2d56b0762570 100644
> > --- a/Documentation/iio/ad4000.rst
> > +++ b/Documentation/iio/ad4000.rst
> > @@ -191,3 +191,20 @@ Typical voltage channel attributes of a differential AD4000 series device:
...
> > +SPI offload support
> > +-------------------
> > +
> > +To be able to achieve the maximum sample rate, the driver can be used with the
> > +`AXI SPI Engine`_ to provide SPI offload support.
> 
> Can we make this more generic?  
> "the driver can be used with SPI offload engine, such as the ...
> 
> I'm rather hoping we see others in the long run as useful little things!

Okay, will do.
> > +
> > +.. _AXI SPI Engine: http://analogdevicesinc.github.io/hdl/projects/pulsar_adc/index.html
> > +