[PATCH 0/6] iio: adc: ltc2497: add LTC2493 support and line-frequency rejection

[Andrei Stancovici via B4 Relay]

This series adds LTC2493 support to the ltc2497 driver, and adds FA/FB
line-frequency rejection for the LTC2499 and the LTC2493.

It includes:
- the LTC2493 device-tree binding,
- LTC2493 support in the driver: 4 single-ended inputs or 2 differential
  pairs, 24-bit result, same command format as the LTC2499,
- the LTC2493 internal PTAT temperature channel,
- the LTC2493 2x conversion speed mode, exposed via sampling_frequency,
- FA/FB line-frequency rejection (50Hz, 60Hz, or both) exposed via
  filter_mode, implemented in the core and enabled for the LTC2499,
- the same rejection selection enabled for the LTC2493.

The FA/FB patch also widens the conversion-time budget, because 50Hz-only
rejection takes 163.5 ms at 1x and the previous budget was 150 ms; see
that patch for the details.

Validated on a Raspberry Pi 4 running 7.3.0-rc4, over an IIO network
backend, with a DC1010A-A board (LTC2493) and a DC1012A-A board
(LTC2499):
- LTC2493 voltage channels, single-ended and differential,
- LTC2493 temperature raw/scale/offset, with voltage and temperature
  reads interleaved to confirm no sticky PTAT,
- sampling_frequency 1x/2x switching on the LTC2493,
- filter_mode 50Hz/60Hz/both on both parts, with the conversion time
  honoured in each mode,
- pyadi-iio hardware test suites: 41/41 on the LTC2493, 36/36 on the
  LTC2499.

The series was rebased onto the base commit below after those runs. The
rebase left all four touched files byte-identical, so the code posted
here is the code that was tested.

Signed-off-by: Andrei Stancovici <andrei.stancovici@xxxxxxxxxx>
---
Andrei Stancovici (6):
      dt-bindings: iio: adc: lltc,ltc2497: add LTC2493 support
      iio: adc: ltc2497: add LTC2493 support
      iio: adc: ltc2497: add LTC2493 internal temperature channel
      iio: adc: ltc2497: add 2x speed mode support for the LTC2493
      iio: adc: ltc2497: add FA/FB line-frequency rejection selection
      iio: adc: ltc2497: enable line-frequency rejection on LTC2493

 .../devicetree/bindings/iio/adc/lltc,ltc2497.yaml  |   7 +
 drivers/iio/adc/ltc2497-core.c                     | 199 +++++++++++++++++----
 drivers/iio/adc/ltc2497.c                          |  61 +++++--
 drivers/iio/adc/ltc2497.h                          |  45 ++++-
 4 files changed, 251 insertions(+), 61 deletions(-)
---
base-commit: a3b3580713f3ac5a32dc2874ee546828977a1d68
change-id: 20261009-submission-ltc2493-support-v1-86449ede432d

Best regards,
--  
Andrei Stancovici <andrei.stancovici@xxxxxxxxxx>