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

[MarileneGarcia]

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

[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.

[jonathanns]

Just a few more notes.

[MarileneGarcia]

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]

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.

[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]

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.

[MarileneGarcia]

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.

[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]

Hi @MarileneGarcia,

This initial driver version looks very good.
I'm leaving a few suggestions.
Aside from a few potentially buggy things, most of the comments are about code style nitpicking.

My advise is to address those last nits and send it to the mailing lists. Experienced kernel maintainers may find further possible improvements for this driver but I do think this is a very good starting point for upstream review.

[machschmitt]

hmm, did you really need that? I think it's unlikely that rpi5 SPI controller actually supports 16 bits_per_word since rpi4 SPI controller only supported 8 bits_per_word. I would just drop bits_per_word = 16, unless somehow rpi5 supports it and register read stops working without that.

[MarileneGarcia]

Hi @MarileneGarcia,

This initial driver version looks very good. I'm leaving a few suggestions. Aside from a few potentially buggy things, most of the comments are about code style nitpicking.

My advise is to address those last nits and send it to the mailing lists. Experienced kernel maintainers may find further possible improvements for this driver but I do think this is a very good starting point for upstream review.

Okay, I believe I’ve addressed them, but I’ll wait for your approval before sending the patches to the maintainers.
Thank you.

[machschmitt]

Okay, I believe I’ve addressed them, but I’ll wait for your approval before sending the patches to the maintainers.

The patches look great. But, unfortunately, they don't apply to IIO testing branch. The patches need to be ported to the testing branch of IIO tree. It should not be hard to port the patches by editing the git hunks.
Change patch1 hunk to be like

@@ -14952,6 +14952,13 @@ F:	drivers/iio/amplifiers/hmc425a.c
 F:	Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
 F:	drivers/iio/adc/max11205.c
 
+ANALOG DEVICES INC MAX14001 DRIVER
+M:	Marilene Andrade Garcia <[email protected]>
+L:	[email protected]
+S:	Maintained
+W:	https://ez.analog.com/linux-software-drivers
+F:	Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
+
 MAXIM MAX17040 FAMILY FUEL GAUGE DRIVERS
 R:	Iskren Chernev <[email protected]>
 R:	Krzysztof Kozlowski <[email protected]>

change patch2 to be like

@@ -14958,6 +14958,7 @@ L:	[email protected]
 S:	Maintained
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml
+F:	drivers/iio/adc/max14001.c
 
 MAXIM MAX17040 FAMILY FUEL GAUGE DRIVERS
 R:	Iskren Chernev <[email protected]>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index d3d12ed064e5..22b348bb675a 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -979,6 +979,16 @@ config MAX11205
 	  To compile this driver as a module, choose M here: the module will be
 	  called max1363.
 
+config MAX14001
+	tristate "Analog Devices MAX14001/MAX14002 ADCs driver"
+	depends on SPI
+	help
+	  Say yes here to build support for Analog Devices MAX14001/MAX14002
+	  Configurable, Isolated 10-bit ADCs for Multi-Range Binary Inputs.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called max14001.
+
 config MAX34408
 	tristate "Maxim max34408/max344089 ADC driver"
 	depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 6a71631c9842..bc4c6d7a57dd 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -86,6 +86,7 @@ obj-$(CONFIG_MAX11205) += max11205.o
 obj-$(CONFIG_MAX11410) += max11410.o
 obj-$(CONFIG_MAX1241) += max1241.o
 obj-$(CONFIG_MAX1363) += max1363.o
+obj-$(CONFIG_MAX14001) += max14001.o
 obj-$(CONFIG_MAX34408) += max34408.o
 obj-$(CONFIG_MAX77541_ADC) += max77541-adc.o
 obj-$(CONFIG_MAX9611) += max9611.o

We may talk more about it at next week's meeting.