iio: adc: Add initial driver support for MAX14001/MAX14002 #2848

MarileneGarcia · 2025-07-13T23:31:33Z

The MAX14001/MAX14002 are configurable, isolated 10-bit ADCs for multi-range binary inputs.

Datasheet:
Link: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf

PR Description

Basic IIO ADC max14001 driver features:

Definitions for register addresses and useful constants (if any).
Definitions for the IIO channels.
Device state struct.
read_raw and write_raw function implementations (just a mock for now).
iio_info struct populated with a reference to the read_raw and write_raw functions.
Probe function to initialize and make basic setup for the device.
SPI and device tree MODULE_DEVICE_TABLEs
Device tree overlay for Raspberry Pi 5
Basic max14001 SPI read and write functions

PR Type

New feature (a change that adds new functionality)

PR Checklist

I have conducted a self-review of my own code changes
I tested it on the Raspberry Pi, but without the max14001 board, I couldn't fully validate it yet.
Evidence of some basic features working

The MAX14001/MAX14002 are configurable, isolated 10-bit ADCs for multi-range binary inputs. Datasheet: Link: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

machschmitt

Hi @MarileneGarcia , a few comments about this initial driver version.
Note that, aside from the comments above, there are still some improvements that need to be made to make this driver usable (e.g. read ADC sample data, provide scale to convert output codes to mV). Those features shall be implemented next. Though, overall, this looks good to me as an initial driver version.

arch/arm/boot/dts/overlays/rpi-max14001-overlay.dts

drivers/iio/adc/max14001.c

jonathanns

Just a few more notes.

drivers/iio/adc/max14001.c

MarileneGarcia · 2025-07-20T15:17:21Z

Hi @MarileneGarcia , a few comments about this initial driver version. Note that, aside from the comments above, there are still some improvements that need to be made to make this driver usable (e.g. read ADC sample data, provide scale to convert output codes to mV). Those features shall be implemented next. Though, overall, this looks good to me as an initial driver version.

Ok, thank you for the comments! I think I have address them. I will start working in the other needed features, like the read ADC sample data and provide scale to convert output codes to mV.

MarileneGarcia · 2025-07-20T15:45:06Z

Just a few more notes.

Ok, thank you for the comments! I think I have address them. The ones related to the write_raw I am going to check in the next steps.

- Update the ovelay file to reflect the evaluation board name - Add Vddl and Vrefin regulators to the overlay file - Update the log print methods - Remove unnecessary code - Improve code style - Add chip_info struct - Add max14001_spi_write_single_reg method, which enables and disables the write register when writing data to another register Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

machschmitt

Looks good to me.

A few more comments.
The regulator thing can be done on a different PR (we might need to rebase or create another GSoC branch if updating to kernel 6.12).

Keep up the good work.

machschmitt · 2025-07-20T19:02:33Z

drivers/iio/adc/max14001.c

+{
+	int ret;
+
+	//Enable register write


Use IIO subsystem preferred comment style:

- //Enable register write + /* Enable register write */

machschmitt · 2025-07-20T19:03:13Z

drivers/iio/adc/max14001.c

+	if (ret < 0)
+		return ret;
+
+	//Write data into register


Same here

- //Write data into register + /* Write data into register */

machschmitt · 2025-07-20T19:03:20Z

drivers/iio/adc/max14001.c

+	if (ret < 0)
+		return ret;
+
+	//Disable register write


machschmitt · 2025-07-20T19:22:07Z

drivers/iio/adc/max14001.c

+	indio_dev->name = st->chip_info->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &max14001_info;
+


Missed it on my first review, but the driver needs to get the voltage regulators during probe.
IIRC, vdd and vddl are required while vrefin is not. If so, I'd suggest using devm_regulator_get_enable() to get vdd and vddl, and devm_regulator_get_enable_read_voltage() for vrefin. See drivers/regulator/devres.c, https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/tree/drivers/iio/adc/ad7191.c#n130 , for example.

PS.: those regulator_get_... calls may not be available in kernel 6.6. If so, you can either (1) use devm_regulator_get(), regulator_enable(), and regulator_get_voltage(), or (2) update to a newer kernel and look for that API. We have a newer rpi branch now, https://github.com/analogdevicesinc/linux/tree/staging-rpi/rpi-6.12.y

Slight preference for (2), but option (1) is also fine for now.

machschmitt · 2025-07-20T19:30:35Z

drivers/iio/adc/max14001.c

+
+	/* TODO: Validate this line in the hw, could be le16_to_cpu */
+	reversed = bitrev16(be16_to_cpu(rx));
+	*val = FIELD_GET(MAX14001_MASK_ADDR, reversed);


why MAX14001_MASK_ADDR?
Isn't the intent to read the register data?

Sorry, my mistake. I am going to change that, thanks!

MarileneGarcia requested review from nunojsa, mhennerich, dbogdan, btogorean, chegbeli, buha, amiclaus, rbolboac, danmois, CiprianRegus and machschmitt as code owners July 13, 2025 23:31

MarileneGarcia closed this Jul 13, 2025

MarileneGarcia reopened this Jul 13, 2025

MarileneGarcia force-pushed the rpi-6.6.y_GSOC_2025_MAX14001 branch from 8e965dc to 0ecd86d Compare July 13, 2025 23:58

machschmitt reviewed Jul 17, 2025

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jonathanns reviewed Jul 17, 2025

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MarileneGarcia force-pushed the rpi-6.6.y_GSOC_2025_MAX14001 branch from d29debd to f6eaef5 Compare July 20, 2025 15:37

MarileneGarcia force-pushed the rpi-6.6.y_GSOC_2025_MAX14001 branch from f6eaef5 to b451319 Compare July 20, 2025 15:50

machschmitt approved these changes Jul 20, 2025

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iio: adc: Add initial driver support for MAX14001/MAX14002 #2848

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iio: adc: Add initial driver support for MAX14001/MAX14002 #2848

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MarileneGarcia commented Jul 13, 2025 •

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machschmitt Jul 20, 2025 •

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