[PATCH 6/6] docs: iio: ad4030: add documentation

Esteban Blanc
2024-08-22T12:45:54Z

This adds a new page to document how to use the ad4030 ADC driver

Signed-off-by: Esteban Blanc <eblanc@baylibre.com>
---
Documentation/iio/ad4030.rst | 129 +++++++++++++++++++++++++++++++++++++++++++
Documentation/iio/index.rst | 1 +
MAINTAINERS | 1 +
3 files changed, 131 insertions(+)

diff --git a/Documentation/iio/ad4030.rst b/Documentation/iio/ad4030.rst
new file mode 100644
index 000000000000..56e0ba58b127
--- /dev/null
+++ b/Documentation/iio/ad4030.rst
@@ -0,0 +1,129 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+=============
+AD4030 driver
+=============
+
+ADC driver for Analog Devices Inc. AD4030 and similar devices. The module name
+is ``ad4030``.
+
+
+Supported devices
+=================
+
+The following chips are supported by this driver:
+
+* `AD4030-24 <https://www.analog.com/AD4030-24>`_
+* `AD4630-16 <https://www.analog.com/AD4630-16>`_
+* `AD4630-24 <https://www.analog.com/AD4630-24>`_
+* `AD4632-16 <https://www.analog.com/AD4632-16>`_
+* `AD4632-24 <https://www.analog.com/AD4632-24>`_
+
+IIO channels
+============
+
+Each "device" channel as described in the datasheet is split in 2 IIO channels,
+in the following order:
+
+- One channel for the differential data
+- One channel for the common byte.
+
+Supported features
+==================
+
+SPI wiring modes
+----------------
+
+The driver currently supports the following SPI wiring configurations:
+
+One lane mode
+^^^^^^^^^^^^^
+
+In this mode, each channel has its own SDO line to send the conversion results.
+At the moment this mode can only be used on AD4030 which has one channel so only
+one SDO line is used.
+
+.. code-block::
+
+ +-------------+ +-------------+
+ | ADC | | HOST |
+ | | | |
+ | CNV |<--------| CNV |
+ | CS |<--------| CS |
+ | SDI |<--------| SDO |
+ | SDO0 |-------->| SDI |
+ | SCLK |<--------| SCLK |
+ +-------------+ +-------------+
+
+Interleaved mode
+^^^^^^^^^^^^^^^^
+
+In this mode, both channels conversion results are bit interleaved one SDO line.
+As such the wiring is the same as `One lane mode`.
+
+SPI Clock mode
+--------------
+
+Only the SPI clocking mode is supported.
+
+Output modes
+------------
+
+There is more exposed IIO channels than channels as describe in the devices
+datasheet. This is due to the `Differential data + 8-bit common-mode` encoding
+2 types of information in one conversion result. As such a "device" channel
+provides 2 IIO channels, one for the differential data and one for the common
+byte.
+
+Differential data
+^^^^^^^^^^^^^^^^^
+
+This mode is selected when:
+
+- Only differential channels are selected
+- Oversampling attribute is set to 1
+
+Differential data + common-mode
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This mode is selected when:
+
+- Differential and common-mode channels are selected
+- Oversampling attribute is set to 1
+
+For the 24-bits chips, this mode is also available with 16-bits differential
+data but is not selectable yet.
+
+Averaged differential data
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This mode is selected when:
+
+- Only differential channels are selected
+- Oversampling attribute is greater than 1
+
+Reference voltage
+-----------------
+
+The chip supports an external reference voltage via the ``REF`` input or an
+internal buffered reference voltage via the ``REFIN`` input. The driver looks
+at the device tree to determine which is being used. If ``ref-supply`` is
+present, then the external reference voltage is used and the internal buffer is
+disabled. If ``refin-supply`` is present, then the internal buffered reference
+voltage is used.
+
+Reset
+-----
+
+Both hardware and software reset are supported. The driver looks first at the
+device tree to see if the `reset-gpio` is populated. If not present, the driver
+will fallback to a software reset by wiring to the device's registers.
+
+Unimplemented features
+----------------------
+
+- ``BUSY`` indication
+- Additional wiring modes
+- Additional clock modes
+- Differential data 16-bits + common-mode for 24-bits chips
+
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index dfcf9618568a..61faf3a60da6 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -19,6 +19,7 @@ Industrial I/O Kernel Drivers
:maxdepth: 1

ad4000
+ ad4030
ad4695
ad7380
ad7944
diff --git a/MAINTAINERS b/MAINTAINERS
index 6a5a0e7b7a51..4a076a48648a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -420,6 +420,7 @@ R: Esteban Blanc <eblanc@baylibre.com>
S: Supported
W: https://ez.analog.com/linux-software-drivers
F: Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
+F: Documentation/iio/ad4030.c
F: drivers/iio/adc/ad4030.c

AD5110 ANALOG DEVICES DIGITAL POTENTIOMETERS DRIVER

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2.44.1