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Fri, 21 Aug 2026 10:07:23 -0400 From: Janani Sunil Subject: [PATCH v4 00/14] iio: adc: Add AD7768/AD7768-4 ADC driver support Date: Fri, 21 Aug 2026 16:06:53 +0200 Message-ID: <20260821-ad7768-driver-v4-0-bb8fbd06d4eb@analog.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAH1biGoC/2XM3wrCIByG4VsJjzP057/ZUfcRHZi6TagZGlKM3 XtuENU6/D543hFln4LPaL8ZUfIl5BCHOvh2g2xvhs7j4OpGQEASRRpsnFKywS6F4hOmxDoqQEs LBFVzS74Nj6V3PNXdh3yP6bnkC53fd0mvSoVigjn3lGreOi3NwQzmErudjVc0pwp8eEPkmkPlB JSxwoORnP5x9sUpW3NWuT0LwZnWxoH84dM0vQB3vAdFKQEAAA== X-Change-ID: 20260708-ad7768-driver-10cd15296c20 To: =?utf-8?q?Nuno_S=C3=A1?= , Michael Hennerich , Jonathan Cameron , "David Lechner" , Andy Shevchenko , "Rob Herring" , Krzysztof Kozlowski , "Conor Dooley" , Olivier Moysan , Philipp Zabel , Linus Walleij , Bartosz Golaszewski , Jonathan Corbet , Shuah Khan , Michael Walle CC: , , , , , , , =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , Janani Sunil X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; 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Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad7768-ad7768-4.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. Initialize the AXI ADC state mutex. 2. Add the AD7768 and AD7768-4 devicetree binding. 3. Add the IIO backend CRC operation. 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. Signed-off-by: Janani Sunil --- Changes in v4: - Move the AXI ADC mutex initialization fix to the start of the series. - Clarify the IIO backend CRC documentation for input and output paths. - Add explicit MCLK, crystal, and LVDS clock-source handling and sequencing. - Keep the required channel active for crystal excitation. - Configure FILTER/GPIO4 for crystal and LVDS clock sources and reserve it from GPIO consumers while it is used for clock selection. - Make AVSS optional. - Validate MCLK, crystal, and LVDS clock rates against datasheet limits. - Split each differential reference into positive and negative supplies. - Correct AD7768-4 standby and channel-mode bit handling. - Program the AD7768-4 channel mode-enable bits correctly. - Use unshifted register values and FIELD_PREP() consistently. - Use regmap single-bit helpers where appropriate. - Use scoped runtime-PM guards and scoped loop variables. - Use for_each_set_bit() and named channel-child iteration. - Remove the redundant initial autosuspend request. - Document the validated 20 ms wake-up delay. - Make REGULATOR mandatory when VCM regulator support is introduced. - Add feature dependencies and includes in their respective patches. - Convert gpio-regmap runtime-PM handling to cleanup guards. - Use active-only PM references for gpio-regmap operations. - Mark GPIO chips using runtime PM as sleep-capable. - Simplify the AD7768 GPIO auxiliary driver. - Clean up IIO and kernel coding-style issues across the series. - Drop the redundant Devicetree example. - Update the link to the latest Rev. D datasheet, update table references. - Address the remaining binding description comments. - Link to v3: https://lore.kernel.org/r/20260813-ad7768-driver-v3-0-cb554399ad26@analog.com Changes in v3: - Split the IIO driver into core support and focused patches for sampling modes, calibration, conversion delay, VCM, and GPIO registration. - Split AXI ADC mutex initialization into a separate preparatory patch. - Use PSEC_PER_SEC, explicit frequency units, unsigned frequency storage, 32-bit divider arithmetic, and rounddown_pow_of_two(). - Use endian helpers and bulk regmap operations for calibration transfers, while retaining single-register writes for the custom SPI protocol. - Validate the MCLK rate during probe and reject a zero computed DCLK rate. - Remove redundant SPI and channel-template state, regmap_attach_dev(), unused includes, and a forward declaration, unused chn_mode assignment. - Move regulators additionalProperties and drop redundant GPIO dependencies from the Devicetree binding. - Split the gpio-regmap changes and add the regmap_test_bits() conversion as a separate cleanup. - Limit the generic gpio-regmap extension to optional runtime PM support. - Use an AD7768 reg_mask_xlate() callback to select the output latch for output GPIOs and document why it is required. - Use regmap_test_bits() when reading the VCM enable state. - Use descriptive runtime PM cleanup labels and verify structure layout with pahole. - Set the VCM regulator's regulators_node so constraints from the nested vcm-output node are parsed. - Mark gpio-regmap GPIO chips as sleep-capable when a runtime PM device is configured. - Reword the conversion-delay and buffered-capture documentation to clarify their operation. - Link to v2: https://lore.kernel.org/r/20260806-ad7768-driver-v2-0-027ac5e2a641@analog.com Changes in v2: - Renamed and expanded supply descriptions, split reference to ref1-supply and ref2-supply. - Added START and synchronization signal descriptions. - Added variant-specific channel and data-line validation. - Made adi,data-lines-number optional, defaulting to the maximum. - Renamed the precharge and reference-buffer properties, removed channel mode and power mode properties. - Exposed the VCM output through the regulator framework and updated documentation accordingly. - Improved runtime PM initialization and requested initial autosuspend after probe. - Automatically assigned channels to two hardware mode profiles. - Selected the lowest noise compatible power mode when ODR ranges overlap. - Replaced the raw phase attribute with the standard conversion-delay attribute. - Added filter-settling delays based on the selected filter and ODR. - Fixed AD7768-4 register and channel-bit mapping, including standby, calibration, phase, precharge and reference-buffer handling. - Added direct-mode protection around runtime channel configuration. - Added calibration register range validation and documented calibration values as raw unsigned 24-bit values. - Added the required reset pulse delay derived from MCLK. - Added a generic GPIO-regmap patch providing runtime-PM integration and separate output-register readback. - Converted the AD7768 GPIO auxiliary driver to use gpio-regmap. - Documented that AXI ADC CRC control bit 8 is common to the AXI ADC cores. - Added the missing AXI ADC mutex initialization. - Expanded the driver documentation to describe dynamic channel grouping, power-mode selection, VCM regulation and conversion delay. - Link to v1: https://lore.kernel.org/r/20260709-ad7768-driver-v1-0-44e1194fd96a@analog.com --- Janani Sunil (14): iio: adc: adi-axi-adc: Initialize state mutex dt-bindings: iio: adc: Add AD7768 iio: backend: Add support for CRC iio: adc: adi-axi-adc: Add support for CRC iio: adc: Add AD7768 and AD7768-4 core support iio: adc: ad7768: Add configurable sampling modes iio: adc: ad7768: Add calibration controls iio: adc: ad7768: Add per-channel conversion delay iio: adc: ad7768: Add VCM regulator support iio: adc: ad7768: Register GPIO auxiliary device gpio: regmap: Use regmap_test_bits() for single bit reads gpio: regmap: Add optional runtime PM support gpio: ad7768: Add AD7768 GPIO auxiliary driver Documentation: iio: Add AD7768 Documentation .../devicetree/bindings/iio/adc/adi,ad7768.yaml | 314 ++++ Documentation/iio/ad7768.rst | 259 +++ Documentation/iio/index.rst | 1 + MAINTAINERS | 10 + drivers/gpio/Kconfig | 12 + drivers/gpio/Makefile | 1 + drivers/gpio/gpio-ad7768.c | 118 ++ drivers/gpio/gpio-regmap.c | 82 +- drivers/iio/adc/Kconfig | 15 + drivers/iio/adc/Makefile | 1 + drivers/iio/adc/ad7768.c | 1855 ++++++++++++++++++++ drivers/iio/adc/adi-axi-adc.c | 25 + drivers/iio/industrialio-backend.c | 33 + include/linux/gpio/regmap.h | 2 + include/linux/iio/backend.h | 6 + 15 files changed, 2722 insertions(+), 12 deletions(-) --- base-commit: b75697ef53e435d894833dad2a8c2fa882cb9b19 change-id: 20260708-ad7768-driver-10cd15296c20 Best regards, -- Janani Sunil