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.

drivers/iio/adc/max14001.c

- Add regulators - Provide scale to convert opcodes to mV - Read ADC sample data Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

…CALE return value - Remove max14001_get_scale method - Fix typo Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

machschmitt

Hi @MarileneGarcia , the updates to MAX14001 driver look mostly good to me. I would merge the PR, but I think it will actually be easier to do the suggested changes before merging this rather than doing them later. So, I'll wait until the last adjustments are done to merge this PR.

drivers/iio/adc/max14001.c

MarileneGarcia · 2025-07-27T23:05:31Z

Hi @MarileneGarcia , the updates to MAX14001 driver look mostly good to me. I would merge the PR, but I think it will actually be easier to do the suggested changes before merging this rather than doing them later. So, I'll wait until the last adjustments are done to merge this PR.

Hello @machschmitt. Sure, I have done the requested changes, thank you!
I also submitted the initial version of the device tree documentation. And a new method to set the value of the verification registers, which should be done every time the device powers up.

- Fix memory validation fault related to verification registers values at power-on-reset (POR) - Add device tree documentation for MAX14001/MAX14002 - Move regulators initialization logic to probe function Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

- The read and write functions were tested on actual hardware and both worked fine - Fix the overlay to be correctly read by the driver Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

machschmitt

Hi @MarileneGarcia , a few comments about the dt-bindings and new code. I'll have a closer look at MAX14001 data sheets to provide a more accurate review this weekend.

machschmitt · 2025-08-09T03:03:21Z

Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml

+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0


These are not needed when the ADC nodes don't have child nodes (i.e. when the ADC channels are not described in device tree). Drop those

- '#address-cells': - const: 1 - - '#size-cells': - const: 0

machschmitt · 2025-08-09T03:05:30Z

Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml

+
+  Datasheet can be found here
+    https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf
+


The reference to spi-peripheral-props can be made here

$ref: /schemas/spi/spi-peripheral-props.yaml#

machschmitt · 2025-08-09T03:07:16Z

Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml

+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#


This can then be declared right after the main dt-binding description, as mentioned above.

machschmitt · 2025-08-09T03:29:15Z

drivers/iio/adc/max14001.c

+
+static int max14001_spi_read(struct max14001_state *st, u16 reg, int *val)
+{
+	u16 rx, tx = 0;


IIO subsystem maintainer's preference is to avoid multiple variable declaration with assignment like that.
Instead, split the declarations

- u16 rx, tx = 0; + u16 tx = 0; + u16 rx;

machschmitt · 2025-08-09T03:33:39Z

drivers/iio/adc/max14001.c

+	struct spi_transfer xfer[] = {
+		{
+			.tx_buf = &tx,
+			.len = sizeof(tx),
+			.bits_per_word = 16,
+			.cs_change = 1,
+		},
+		{
+			.rx_buf = &rx,
+			.len = sizeof(rx),
+			.bits_per_word = 16,
+		},
+	};


We normally declare local variables at the beginning of functions. Please, declare xfer close to int ret.

machschmitt · 2025-08-09T03:37:27Z

drivers/iio/adc/max14001.c

+	tx |= FIELD_PREP(MAX14001_MASK_DATA, val);
+	tx = bitrev16(tx);
+
+	struct spi_transfer xfer[] = {


same here, declare xfer nearby int ret. By the way, IIRC, tx_buf and rx_buf will be declared in the state struct so setting xfer buffers will be set differently.

machschmitt · 2025-08-09T03:44:21Z

drivers/iio/adc/max14001.c

+	if (ret < 0) {
+		st->vref_mv = 1250000 / 1000;
+	} else {
+		st->vref_mv = ret / 1000;
+	}


nitpicking: preferred style is to suppress brackets when both if and else blocks have only one line each

if (ret < 0) st->vref_mv = 1250000 / 1000; else st->vref_mv = ret / 1000;

machschmitt · 2025-08-09T03:52:09Z

drivers/iio/adc/max14001.c

+			goto erro_condition;
+
+		/* Write verification register value */
+		val_write_reg = (u16)val_read_reg;


this is a bit odd. I guess declaring u16 val_read_reg lead to build warnings due to max14001_spi_read() taking an int as third argument? I'll have a closer look at MAX14001 and MAX14001PMB data sheets this weekend.

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 new methods for MAX14001/MAX14002 driver

42f812b

- Add regulators - Provide scale to convert opcodes to mV - Read ADC sample data Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

MarileneGarcia force-pushed the rpi-6.6.y_GSOC_2025_MAX14001 branch from d83610c to 42f812b Compare July 24, 2025 11:01

iio: adc: Correct some values to properly reflect the IIO_CHAN_INFO_S…

b77c248

…CALE return value - Remove max14001_get_scale method - Fix typo Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

machschmitt approved these changes Jul 27, 2025

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MarileneGarcia force-pushed the rpi-6.6.y_GSOC_2025_MAX14001 branch from 81f5aa9 to 6c5e260 Compare July 27, 2025 23:39

iio: adc: Fix read and write functions

295b094

- The read and write functions were tested on actual hardware and both worked fine - Fix the overlay to be correctly read by the driver Signed-off-by: Marilene A Garcia <marilene.agarcia@gmail.com>

MarileneGarcia force-pushed the rpi-6.6.y_GSOC_2025_MAX14001 branch from 3bd2356 to 295b094 Compare August 7, 2025 01:06

machschmitt requested changes Aug 9, 2025

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		Datasheet can be found here
		https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf

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 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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MarileneGarcia commented Jul 20, 2025

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MarileneGarcia commented Jul 27, 2025

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MarileneGarcia commented Jul 13, 2025 •

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