[PATCH v5 0/9] iio: adc: ad7606: add support for AD7606C-{16,18} parts

[Alexandru Ardelean <aardelean@baylibre.com>]

The AD7606C-16 and AD7606C-18 are pretty similar with the AD7606B.
The main difference between AD7606C-16 & AD7606C-18 is the precision in
bits (16 vs 18).
Because of that, some scales need to be defined for the 18-bit variants, as
they need to be computed against 2**18 (vs 2**16 for the 16 bit-variants).

Because the AD7606C-16,18 also supports bipolar & differential channels,
for SW-mode, the default range of 10 V or ±10V should be set at probe.
On reset, the default range (in the registers) is set to value 0x3 which
corresponds to '±10 V single-ended range', regardless of bipolar or
differential configuration.

Aside from the scale/ranges, the AD7606C-16 is similar to the AD7606B.

This changeset, does a bit of rework to the existing ad7606 driver and then
adds support for the AD7606C-16 & AD7606C-18 parts.

Datasheet links:
  https://www.analog.com/media/en/technical-documentation/data-sheets/ad7606c-16.pdf
  https://www.analog.com/media/en/technical-documentation/data-sheets/ad7606c-18.pdf

Changelog v4 -> v5:
  - v4: https://lore.kernel.org/linux-iio/20240905082404.119022-1-aardelean@baylibre.com/
  - Not all topics from v4 have been fully resolved; but I created a v5 in
    case it helps to spot other (new) topics
  - Added patch 'iio: adc: ad7606: remove frstdata check for serial mode'
    - This is from the 'fixes-togreg' branch
    - It should be ignored
    - Should help with a bit of context for this series
  - For patch 'iio: adc: ad7606: add 'bits' parameter to channels macros'
    - Added '.storagebits = (bits) > 16 ? 32 : 16'
    - Reduces the final patch a bit
      - i.e. 'iio: adc: ad7606: add support for AD7606C-{16,18} parts'
  - For patch 'iio: adc: ad7606: move 'val' pointer to ad7606_scan_direct() '
    - Added 'Reviewed-by: David Lechner <dlechner@baylibre.com>'
  - For patch 'iio: adc: ad7606: rework available attributes for SW channels'
    - Added '.storagebits = (bits) > 16 ? 32 : 16'
    - Reduces the final patch a bit
      - i.e. 'iio: adc: ad7606: add support for AD7606C-{16,18} parts'
  - For patch 'dt-bindings: iio: adc: add docs for AD7606C-{16,18} parts'
    - Added '"^channel@[1-8]$": false' if not 'adi,sw-mode'
    - Added 'Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>'
    - Given the change, I would need confirmation that the Krzysztof's
      Reviewed-by tag is still valid
    - There is still an open topic about using
      'oneOf:required:{diff-channels,bipolar}' vs 
      'if:required: [diff-channels]then:required: [bipolar]'
      - I'm leaning towards 'oneOf:required:{diff-channels,bipolar}'
      - Let's see what a discussio will yield
  - For patch 'iio: adc: ad7606: add support for AD7606C-{16,18} parts'
    - In 'ad7606_spi_read_block18to32()' fixed 
       '.len = count * sizeof(uint32_t)' in 'struct spi_transfer xfer'
    - In 'ad7606_read_samples()' changed 'u16 *data = st->data;' to
      'void *data = st->data.d16;' ; both would compile though ;
      converting 'data' to 'void *' may show that it's not just 16 bits
    - In ad7606c_18_chan_setup() & ad7606c_16_chan_setup()
      - Added explicit 'cs->reg_offset = 0;'
    - In 'ad7606c_sw_mode_setup_channels()' :
      - If pins are specified incorrectly, an error is triggered (vs
        ignoring it before)
      - Updated comment about why 'st->bops->sw_mode_config()' is called
        first

Changelog v3 -> v4:
  - v3: https://lore.kernel.org/linux-iio/20240904072718.1143440-1-aardelean@baylibre.com/
  - For patch 'dt-bindings: iio: adc: document diff-channels corner case
    for some ADCs'
    - Added 'Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>'
  - Renamed patch 'dt-bindings: iio: adc: add adi,ad7606c-{16,18} compatible strings'
    to 'dt-bindings: iio: adc: add docs for AD7606C-{16,18} parts'
    - Updated based on notes from Krzysztof Kozlowski (from v3)
      - Dropped ()
      - Re-ordered the patternProperties:oneOf:required specification
      - Unified match-pattern to '^channel@[1-8]$'

Changelog v2 -> v3:
  - v2: https://lore.kernel.org/linux-iio/20240902103638.686039-1-aardelean@baylibre.com/
  - Applied checkpatch.pl changes
  - Managed to setup and run 'make dt_binding_check DT_SCHEMA_FILES=adi,ad7606.yaml'
    - Found the winning combination for this setup
    - David Lechner also helped
  - For patch 'iio: adc: ad7606: rework available attributes for SW channels'
    - Removed an extra space that checkpatch found
  - For patch 'dt-bindings: iio: adc: document diff-channels corner case
    for some ADCs'
    - Removed 'the the' stutter (that I did in writing)
  - For patch 'dt-bindings: iio: adc: add adi,ad7606c-{16,18} compatible strings'
    - Updated binding with some description for 'diff-channels' & 'bipolar'
      properties
    - Channel definitions are counted from 1 to 8 to match datasheet
    - Added more bindings rules for 'diff-channels' & 'bipolar' for AD7606C
      - Adapted some ideas from adi,ad7192.yaml
  - For patch 'iio: adc: ad7606: add support for AD7606C-{16,18} parts'
    - Updated 'diff-channels' property with channel numbers (from 1 to 8)
      handling

Changelog v1 -> v2:
  - v1: https://lore.kernel.org/linux-iio/20240819064721.91494-1-aardelean@baylibre.com/
  - Fixed description in 'iio: adc: ad7606: add 'bits' parameter to channels macros'
  - Added patch 'dt-bindings: iio: adc: document diff-channels corner case
    for some ADCs'
    - diff-channels = <reg reg> can be used to define differential channels
      with dedicated positive + negative pins
  - Re-worked patch 'dt-bindings: iio: adc: add adi,ad7606c-{16,18} compatible strings'
    - Using standard 'diff-channels' & 'bipolar' properties from adc.yaml
  - Re-worked patch 'iio: adc: ad7606: add support for AD7606C-{16,18} parts'
    - Reading 18-bit samples now relies on SPI controllers being able to
      pad 18-bits to 32-bits.
    - Implemented 'diff-channels = <reg reg>' setting
    - Removed some bad/left-over channel configuration code which I forgot
      during development and rebasing.

Alexandru Ardelean (8):
  iio: adc: ad7606: add 'bits' parameter to channels macros
  iio: adc: ad7606: move 'val' pointer to ad7606_scan_direct()
  iio: adc: ad7606: split a 'ad7606_sw_mode_setup()' from probe
  iio: adc: ad7606: wrap channel ranges & scales into struct
  iio: adc: ad7606: rework available attributes for SW channels
  dt-bindings: iio: adc: document diff-channels corner case for some
    ADCs
  dt-bindings: iio: adc: add docs for AD7606C-{16,18} parts
  iio: adc: ad7606: add support for AD7606C-{16,18} parts

Guillaume Stols (1):
  iio: adc: ad7606: remove frstdata check for serial mode

 .../devicetree/bindings/iio/adc/adc.yaml      |   4 +
 .../bindings/iio/adc/adi,ad7606.yaml          | 117 +++++
 drivers/iio/adc/ad7606.c                      | 432 ++++++++++++++----
 drivers/iio/adc/ad7606.h                      |  80 +++-
 drivers/iio/adc/ad7606_par.c                  |  48 +-
 drivers/iio/adc/ad7606_spi.c                  |  71 ++-
 6 files changed, 633 insertions(+), 119 deletions(-)

-- 
2.46.0