Re: [PATCH v3 00/14] iio: adc: Add AD7768/AD7768-4 ADC driver support

On Thu, Aug 13, 2026 at 03:56:53PM +0200, Janani Sunil wrote:

Add support for Analog Devices AD7768 and AD7768-4, 24-bit simultaneous
sampling Sigma-Delta ADCs with automatic power mode selection.

Datasheet:
https://www.analog.com/media/en/technical-documentation/data-sheets/ad7768.pdf

**Device Overview:**
The AD7768 is an 8-channel, 24-bit simultaneous sampling ADC. The
AD7768-4 is a 4-channel variant. Both support configurable power modes,
programmable decimation filters, and a high-speed serial interface with
1, 2, 4, or 8 data output lines. Per-channel offset, gain, and phase
calibration registers are available.

**Features Implemented:**
- Support for AD7768 (8-channel) and AD7768-4 (4-channel) via device
  match data.
- Automatic low-noise power mode selection (fast, median, low power)
  with associated decimation rate and output data rate tables.
- Per-channel offset, gain, and conversion delay via IIO attributes.
- SPI communication with custom regmap bus for the device's protocol.
- IIO backend integration with adi-axi-adc for high-speed data capture.
- CRC data integrity verification over the serial interface.
- GPIO auxiliary driver to expose the 5 on-chip GPIO pins.
- VCM common-mode output exposed through the regulator framework, with
  runtime PM management while the output is enabled.

**Patch Summary:**
1. Add the AD7768 and AD7768-4 devicetree binding.
2. Add the IIO backend CRC operation.
3. Initialize the AXI ADC state mutex.
4. Implement CRC control in the AXI ADC backend.
5. Add core AD7768 and AD7768-4 capture support.
6. Add configurable sampling rates, power modes, and filters.
7. Add per-channel offset and gain calibration controls.
8. Add per-channel conversion delay.
9. Expose the VCM output through the regulator framework.
10. Register the GPIO auxiliary device from the parent driver.
11. Use regmap_test_bits() for single-bit gpio-regmap reads.
12. Add optional runtime PM support to gpio-regmap.
13. Add the AD7768 GPIO auxiliary driver.
14. Add driver documentation.

**Testing:**
The driver was compiled and tested on the EVAL-AD7768FMCZ using a
Zedboard with a mainline kernel.

**Driver Rationale:**
The AD7768/AD7768-4 warrants its own driver due to several
device-specific characteristics:

1. A custom SPI framing protocol: register reads and writes use 16-bit
   frames with embedded read/write bits and register address fields,
   requiring a custom regmap bus implementation rather than the standard
   SPI regmap backend.

2. A coupled power mode / sample rate model: available output data rates
   are not a flat list but depend on the active power mode (fast, median,
   low power), each with its own set of valid decimation rates. This
   relationship must be managed in the driver.

3. Simultaneous sampling across all channels with per-channel calibration
   registers (24-bit offset, gain, and phase) that are laid out
   differently between the 8-channel AD7768 and the 4-channel AD7768-4,
   requiring device-specific register mapping.

4. IIO backend integration for high-speed data capture via adi-axi-adc,
   including CRC data integrity verification over the serial interface.

5. On-chip GPIO: 5 general-purpose I/O pins exposed via an auxiliary bus
   driver, sharing the parent's regmap and runtime PM.

The GPIO driver looks nice, but regmap API should use cleanup.h instead of
custom (legacy) approach.

-- 
With Best Regards,
Andy Shevchenko