[PATCH v3 00/13] iio: adc: ad4134: Enable greater sample rate data capture

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

Extend AD4134 support to enable greater sample rate data capture. To achieve
that, provide control of digital filter type selection. The default filter
type on device power up only supports sample rates up to 374 kSPS. In addition
to that, enable interfacing with AD4134 in SPI 4-wire mode that can support
reading ADC sample data through multiple wires. Finally, use SPI offloading
to speed up data transfers at up to 1.49 MSPS.

Features being added:
- Data filter type selection.
- Triggered buffer data read.
- SPI 4-wire mode.
- High speed data capture with SPI offloading.
- Device tree doc updates to reflect previously missing chip characteristics.

Minor improvements (introduced before the new features):
- Adjusted register map range now prevents access to uninitialized local variable. [NEW PATCH]
- Sign extend sample data. 
- Update include list to comply with IWYU principles.
- Serialize single-read operations.
- Run shorter transfers when CRC is disabled.

The updates in v3 are intended to tackle all applicable suggestions from
reviewers and from automated tests/reviews/AI.

Change log v2 -> v3:
[device tree]
- Adjusted spi-rx-bus-width constraints.
- Dropped mux provider from offload example.
- Dropped odr-gpios from offload example.
[IIO]
- Already applied fixes patches have been dropped.
- Fixed off-by-one mistake to avoid access to uninitialized local variable. [NEW PATCH]
- Now using IIO_DECLARE_BUFFER_WITH_TS macro to set properly sized triggered
  buffer storage that includes room for timestamp.
- Now using SPI_MODE_X_MASK to update CPOL/CPHA bits.
- Refactored access mode locking to avoid umpaired calls to
  mux_state_select()/deselect().
- Dropped unreachable code on offload setup.
- Fixed sampling frequency validation check.
- Avoided division by zero when external clock is not provided.
- Follow LIFO teardown order on offload buffer disable.
- Set correct buffer size to read all channels in offload mode.
- Disallowed single-read when setup for SPI offloading.
- Corrected AD4134 IIO Doc to only show the PWM connected to ODR on offload diagrams.

Previous submissions:
  v1: https://lore.kernel.org/linux-iio/cover.1788368334.git.marcelo.schmitt@analog.com/
  v2: https://lore.kernel.org/linux-iio/cover.1789494473.git.marcelo.schmitt@analog.com/

With best regards,
Marcelo

Marcelo Schmitt (13):
  iio: adc: ad4134: Adjust register map range
  iio: adc: ad4134: Sign extend sample data
  iio: adc: ad4134: Update include list to comply with IWYU principles
  iio: adc: ad4134: Serialize single-read operations
  iio: adc: ad4134: Run shorter transfers when CRC is disabled
  iio: adc: ad4134: Add support for digital filter type selection
  iio: adc: ad4134: Support buffered data read
  dt-bindings: iio: adc: adi,ad4134: Document SPI connection mode
  dt-bindings: iio: adc: adi,ad4134: Document external multiplexer usage
  iio: adc: ad4134: Support SPI 4-wire mode
  dt-bindings: iio: adc: adi,ad4134: Document PWM usage
  iio: adc: ad4134: Support high-speed data capture
  Docs: iio: Add AD4134

 .../bindings/iio/adc/adi,ad4134.yaml          | 104 ++-
 Documentation/iio/ad4134.rst                  | 128 +++
 Documentation/iio/index.rst                   |   1 +
 MAINTAINERS                                   |   1 +
 drivers/iio/adc/Kconfig                       |   8 +
 drivers/iio/adc/ad4134.c                      | 820 +++++++++++++++++-
 6 files changed, 1027 insertions(+), 35 deletions(-)
 create mode 100644 Documentation/iio/ad4134.rst


base-commit: a3b3580713f3ac5a32dc2874ee546828977a1d68
-- 
2.53.0