[v9,0/8] Support ROHM BD79124 ADC

Message

Matti Vaittinen March 20, 2025, 8:20 a.m. UTC

Support ROHM BD79124 ADC.

This series adds also couple of IIO ADC helper functions for parsing the
channel information from the device tree. There are also new helpers
included for iterating and counting firmware child nodes with a specific
name.

The rzg2l_adc and the sun20i-gpadc are converted to use the new ADC helper.

There has been some discussion about how useful these ADC helpers are,
and whether they should support also differential and single ended channel
configurations. This version does not include support for those - with the
benefit of reduced complexity and easier to use API.

NOTE: The rzg2l_adc and the sun20i-gpadc are untested as I lack of relevant
HW. They have been compile tested only.

The ROHM BD79124 ADC itself is quite usual stuff. 12-bit, 8-channel ADC
with threshold monitoring.

Except that:
 - each ADC input pin can be configured as a general purpose output.
 - manually starting an ADC conversion and reading the result would
   require the I2C _master_ to do clock stretching(!) for the duration
   of the conversion... Let's just say this is not well supported.
 - IC supports 'autonomous measurement mode' and storing latest results
   to the result registers. This mode is used by the driver due to the
   "peculiar" I2C when doing manual reads.

Furthermore, the ADC uses this continuous autonomous measuring,
and the IC keeps producing new 'out of window' IRQs if measurements are
out of window - the driver disables the event for 1 seconds when sending
it to user. This prevents generating storm of events

Revision history:

v8 => v9:
 - Drop the gianfar and the thp7312 drivers from the series to limit the
   review noise and to simplify the merging. They can be submitted later
   as separate changes.
 - Drop the fwnode_for_each_available_named_child() as suggested by
   Sakari.
 - BD79124 driver styling and fixes

v7 => v8:
  property helpers:
    - Fix the example in fwnode_get_named_child_node_count() documentation
      to use the fwnode_get_named_child_node_count() and not the
      device_get_named_child_node_count()
    - Fix the rest of the new macro's indentiations
  adc helpers:
    - Treat 0 ADC channels as an error in
      devm_iio_adc_device_alloc_chaninfo_se().
  rzg2l_adc / sun20i-gpadc:
    - Drop zero channels check from the ADC drivers using
      devm_iio_adc_device_alloc_chaninfo_se()
  BD79124:
    - Use unsigned for regmap values
    - Commit message fine tuning
    - Check devm_mutex_init() return value
    - Handle 'ALL pins as ADC or GPO' cleanly in BD79124 driver
    - BD79124 styling / typofixes

v6 => v7:
 - Inline device_get_named_child_node_count()
 - Fix kernel-doc for fwnode_get_named_child_node_count()
 - Minor styling fixes
 More accurate changelog in individual patches.

v5 => v6:
 - Drop applied patch
 - Add *_for_each_named_child_* iterators
 - Add a patch converting the thp7312 driver to use the new helper
 - Styling and minor things pointed by reviewers

v4 => v5: Fixes as per various review comments. Most notably:
 - Drop the patch making the TI's ADC driver to respect device tree.
 - Add (RFC) patch converting gianfar driver to use new name child-node
   counting API as suggested by Andy.
 - Add fwnode_get_child_node_count_named() as suggested by Rob.
 - rebase to v6.14-rc5
 More accurate changelog in individual patches.

v3 => v4:
 - Drop the ADC helper support for differential channels
 - Drop the ADC helper for getting only channel IDs by fwnode.
 - "Promote" the function counting the number of child nodes with a
   specific name to the property.h (As suggested by Jonathan).
 - Add ADC helpers to a namespace.
 - Rebase on v6.14-rc3
 - More minor changes described in individual patches.

v2 => v3:
 - Restrict BD79124 channel numbers as suggested by Conor and add
   Conor's Reviewed-by tag.
 - Support differential and single-ended inputs
 - Convert couple of existing drivers to use the added ADC helpers
 - Minor fixes based on reviews
Link to v2:
https://lore.kernel.org/all/[e-mail]/

RFC v1 => v2:
 - Drop MFD and pinmux.
 - Automatically re-enable events after 1 second.
 - Export fwnode parsing helpers for finding the ADC channels.

---

Matti Vaittinen (8):
  dt-bindings: ROHM BD79124 ADC/GPO
  property: Add functions to iterate named child
  iio: adc: add helpers for parsing ADC nodes
  iio: adc: rzg2l_adc: Use adc-helpers
  iio: adc: sun20i-gpadc: Use adc-helpers
  iio: adc: Support ROHM BD79124 ADC
  MAINTAINERS: Add IIO ADC helpers
  MAINTAINERS: Add ROHM BD79124 ADC/GPO

 .../bindings/iio/adc/rohm,bd79124.yaml        |  114 ++
 MAINTAINERS                                   |   12 +
 drivers/base/property.c                       |   27 +
 drivers/iio/adc/Kconfig                       |   17 +
 drivers/iio/adc/Makefile                      |    3 +
 drivers/iio/adc/industrialio-adc.c            |   82 ++
 drivers/iio/adc/rohm-bd79124.c                | 1138 +++++++++++++++++
 drivers/iio/adc/rzg2l_adc.c                   |   39 +-
 drivers/iio/adc/sun20i-gpadc-iio.c            |   39 +-
 include/linux/iio/adc-helpers.h               |   27 +
 include/linux/property.h                      |   20 +
 11 files changed, 1470 insertions(+), 48 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/rohm,bd79124.yaml
 create mode 100644 drivers/iio/adc/industrialio-adc.c
 create mode 100644 drivers/iio/adc/rohm-bd79124.c
 create mode 100644 include/linux/iio/adc-helpers.h


base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6