[PATCH v4 0/2] iio: adc: Add Nuvoton MA35D1 EADC support

[Chi-Wen Weng <cwweng.linux@gmail.com>]

From: Chi-Wen Weng <cwweng@nuvoton.com>

This series adds IIO support for the Enhanced Analog-to-Digital
Converter (EADC) found on Nuvoton MA35D1 SoCs.

The EADC provides eight external analog inputs which may be used as
single-ended inputs or as four fixed differential pairs: 0-4, 1-5,
2-6 and 3-7.

The initial driver supports direct conversion and triggered buffered
capture using sample module 0. Although the hardware provides multiple
sample modules, this version of the driver uses only sample module 0
and therefore supports one active voltage channel per buffered scan.

The series is based on Linux v7.4-rc1.

Changes in v4:
- Use the common ADC diff-channels property to describe differential
  inputs and keep reg as the logical channel index.
- Restrict differential inputs to the four hardware-supported pairs.
- Restrict channel child nodes to the ADC properties supported by the
  MA35D1 EADC.
- Prevent single-channel and diff-channels from being specified
  together.
- Document that each single-ended input and differential input pair
  may be described only once.
- Remove interrupt-names and simplify the interrupt descriptions.
- Update the binding example to demonstrate separation of the logical
  channel index from the physical ADC inputs.
- Update channel parsing to match the revised binding semantics.
- Store physical ADC inputs in the IIO channel/channel2 fields and use
  address for the logical DT channel index.
- Reject duplicate physical single-ended inputs and differential input
  pairs.
- Use the physical positive input when programming the sample-module
  channel selection and the logical index for firmware-node channel
  translation.
- Use interrupt index 0 instead of looking up ADINT0 by name.
- Add the standard one-hot scan-mask validation callback.
- Use iio_for_each_active_channel() when selecting the buffered
  channel.
- Use a fixed scan structure for the single-channel buffered layout.
- Limit conversion results to the 12-bit ADC data width.
- Always report -ETIMEDOUT when a conversion times out.
- Make timeout recovery best effort so interrupt disable, control reset,
  IRQ synchronization and stale status cleanup are all attempted even
  if an earlier recovery step fails.
- Use devm_regulator_get_enable_read_voltage() for the optional
  external reference supply.
- Rework clock management to explicitly balance prepare/enable state
  across probe, suspend, resume, error paths and driver teardown.
- Improve suspend and resume error-path handling.
- Remove the redundant explicit REGCACHE_NONE setting.
- Split interrupt status read failures from interrupt-source checks and
  handle failures when clearing the interrupt status.
- Use symbolic definitions for the ADC resolution and differential
  scale width.
- Use cleanup guards for mutex handling in buffered capture and keep
  trigger notification outside the locked section.
- Use more specific error codes for channel capacity, duplicate channel
  definitions and out-of-range physical inputs.
- Apply the requested regmap, control-flow and coding-style cleanups.

Changes in v3:
- Document all four ADINT0 through ADINT3 hardware interrupt outputs and
  add interrupt-names.
- Document ADINT3 as the shared conversion and result-compare interrupt
  output.
- Remove the redundant minItems/maxItems constraints from the fixed
  interrupts items list.
- Rework the channel binding for the fixed differential pairs and use
  single-channel for single-ended inputs.
- Add #io-channel-cells so the EADC can be referenced by DT IIO
  consumers, and define the cell as the logical channel index.
- Add firmware-node channel translation so sparse or reordered channel
  child nodes are mapped by their logical channel index.
- Restrict unsupported generic ADC channel properties including bipolar,
  common-mode-channel, settling-time-us and oversampling-ratio.
- Explicitly configure INTPOS for end-of-conversion interrupt
  generation.
- Explicitly configure the ADINT0 sample-module source and clear unused
  sample-module routing.
- Reset the EADC control circuits during hardware initialization and
  clear inherited ADC interrupt enables, result-compare interrupt
  enables and sample-module trigger sources.
- Add timeout recovery using the EADC control-circuit reset, followed by
  IRQ synchronization and stale status/completion cleanup.
- Use iio_push_to_buffers_with_ts() for triggered buffered capture.
- Avoid mixing cleanup guards with goto paths in the trigger handler.
- Add ARCH_MA35 || COMPILE_TEST and HAS_IOMEM Kconfig dependencies.
- Drop redundant linux/bitops.h and linux/mod_devicetable.h includes.
- Use direct regmap helpers, explicit REGCACHE_NONE and
  regmap_assign_bits() where appropriate.
- Use fixed-width register offsets and kernel time/unit helpers.
- Use size_add() for channel array allocation.
- Request ADINT0 by interrupt name.
- Improve system suspend and resume handling.
- Address review comments from Jonathan Cameron, Rob Herring,
  Andy Shevchenko, Uwe Kleine-König and automated review/testing.

Changes in v2:
- Reworked the driver to use regmap.
- Added optional external reference supply support and IIO scale
  reporting.
- Added optional reset handling.
- Added externally triggered buffered capture.
- Added signed differential conversion handling.
- Added fixed differential-pair validation.
- Added system sleep support.
- Added optional DMA properties to the binding.

Patch 1 adds the devicetree binding.
Patch 2 adds the IIO driver.

Chi-Wen Weng (2):
  dt-bindings: iio: adc: Add Nuvoton MA35D1 EADC
  iio: adc: Add Nuvoton MA35D1 EADC driver

 .../bindings/iio/adc/nuvoton,ma35d1-eadc.yaml | 163 ++++
 drivers/iio/adc/Kconfig                       |  14 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/ma35d1_eadc.c                 | 912 ++++++++++++++++++
 4 files changed, 1090 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/nuvoton,ma35d1-eadc.yaml
 create mode 100644 drivers/iio/adc/ma35d1_eadc.c


base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.25.1