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doc: iio: ad7606: describe offload support

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Add a section to the ad7606 documentation describing how to use the
driver with SPI offloading.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250403-wip-bl-spi-offload-ad7606-v1-2-1b00cb638b12@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Angelo Dureghello 2025-04-03 18:19:05 +02:00 committed by Jonathan Cameron
parent 81fe5529e8
commit 89e1f95a61
1 changed files with 45 additions and 0 deletions
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45
Documentation/iio/ad7606.rst
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@ -26,6 +26,35 @@ SPI wiring modes
These ADCs can output data on several SDO lines (1/2/4/8). The driver
currently supports only 1 SDO line.
SPI offload wiring
------------------
When used with a SPI offload, the supported wiring configuration is:
.. code-block::
+-------------+ +-------------+
| BUSY |-------->| TRIGGER |
| CS |<--------| CS |
| | | |
| ADC | | SPI |
| | | |
| SDI |<--------| SDO |
| DOUTA |-------->| SDI |
| SCLK |<--------| SCLK |
| | | |
| | +-------------+
| CONVST |<--------| PWM |
+-------------+ +-------------+
In this case, the ``pwms`` property is required.
The ``#trigger-source-cells = <1>`` property is also required to connect back
to the SPI offload. The SPI offload will have ``trigger-sources`` property
with a cell to indicate the busy signal:
``<&ad7606 AD4695_TRIGGER_EVENT_BUSY>``.
.. seealso:: `SPI offload support`_
Parallel wiring mode
--------------------
@ -123,6 +152,22 @@ Unimplemented features
- CRC indication
- Calibration
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: https://analogdevicesinc.github.io/hdl/library/spi_engine/index.html
When SPI offload is being used, some attributes will be different.
* ``trigger`` directory is removed.
* ``sampling_frequency`` attribute is added for setting the sample rate.
* ``timestamp`` channel is removed.
* Buffer data format may be different compared to when offload is not used,
e.g. the ``in_voltage0_type`` attribute.
Device buffers
==============