Add MAX14001/MAX14002 support

Add device-tree documentation for MAX14001/MAX14002 ADCs. The MAX14001/MAX14002 are isolated, single-channel analog-to-digital converters with programmable voltage comparators and inrush current control optimized for configurable binary input applications.

Signed-off-by Marilene Andrade Garcia <[email protected]>

---
 .../bindings/iio/adc/adi,max14001.yaml        | 78 +++++++++++++++++++
 MAINTAINERS                                   |  7 ++
 2 files changed, 85 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml

Documentation/devicetree/bindings/iio/adc/adi,max14001.yaml new file +78 -0

new file mode 100644
index 000000000000..3b2a2e788a17
@@ -0,0 +1,78 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2025 Marilene Andrade Garcia
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,max14001.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX14001-MAX14002 10-bit ADCs
+
+maintainers:
+  - Marilene Andrade Garcia <[email protected]>
+
+description:
+  Bindings for the Analog Devices MAX14001-MAX14002 Configurable,
+  Isolated 10-bit ADCs for Multi-Range Binary Inputs.
+
+  Datasheet can be found here
+    https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    enum:
+      - adi,max14001
+      - adi,max14002
+
+  reg:
+    maxItems: 1
+
+  vdd-supply:
+    description:
+      Isolated DC-DC power supply input voltage.
+
+  vddl-supply:
+    description:
+      Logic power supply.
+
+  vrefin-supply:
+    description:
+      ADC voltage reference supply.
+
+  interrupts:
+    items:
+      - description: |
+          Interrupt for signaling when conversion results exceed the configured
+          upper threshold for ADC readings or fall below the lower threshold for
+          them. Interrupt source must be attached to COUT pin.
+      - description: |
+          Alert output that asserts low during a number of different error
+          conditions. The interrupt source must be attached to FAULT pin.
+
+  spi-max-frequency:
+    maximum: 5000000
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+  - vddl-supply
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      max14001: adc@0 {
+        compatible = "adi,max14001";
+        reg = <0>;
+        spi-max-frequency = <5000000>;
+        vdd-supply = <&vdd>;
+        vddl-supply = <&vddl>;
+      };
+    };
+...

MAINTAINERS +7 -1

index af1c8d2bfb3d..0aeab5dbd39d 100644
@@ -14984,6 +14984,13 @@ W:     https://ez.analog.com/linux-software-drivers
 F:     Documentation/devicetree/bindings/iio/adc/maxim,max11205.yaml
 F:     drivers/iio/adc/max11205.c
 
+MAXIM MAX14001/MAX14002 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]>
--

2.34.1

The MAX14001/MAX14002 are configurable, isolated 10-bit ADCs for multi-range binary inputs. Besides the ADC readings, the MAX14001/MAX14002 offers more features, like a binary comparator, a filtered reading that can provide the average of the last 2, 4, or 8 ADC readings, and an inrush comparator that triggers the inrush current. There is also a fault feature that can diagnose seven possible fault conditions. And an option to select an external or internal ADC voltage reference.

Add basic support for MAX14001/MAX14002 with the following features:
- Raw ADC reading.
- Filtered ADC average reading with the default configuration.

Signed-off-by Marilene Andrade Garcia <[email protected]>

---
 MAINTAINERS                |   1 +
 drivers/iio/adc/Kconfig    |  10 ++
 drivers/iio/adc/Makefile   |   1 +
 drivers/iio/adc/max14001.c | 213 +++++++++++++++++++++++++++++++++++++
 4 files changed, 225 insertions(+)
 create mode 100644 drivers/iio/adc/max14001.c

drivers/iio/adc/max14001.c new file +0 -0

new file mode 100644
index 000000000000..fb79f3b81e0c

drivers/iio/adc/max14001.c new file +10 -0

+#include <linux/spi/spi.h>
+#include <linux/iio/iio.h>
+#include <linux/regulator/consumer.h>
+
+/* MAX14001 registers definition */
+#define MAX14001_REG_ADC				0x00
+#define MAX14001_REG_FADC				0x01
+#define MAX14001_REG_FLAGS				0x02
+#define MAX14001_REG_FLTEN				0x03
+#define MAX14001_REG_THL				0x04

drivers/iio/adc/max14001.c new file +10 -0

+#define MAX14001_MASK_ADDR				GENMASK(15, 11)
+#define MAX14001_MASK_WR				BIT(10)
+#define MAX14001_MASK_DATA				GENMASK(9, 0)
+
+enum max14001_chip_model {
+	max14001,
+	max14002,
+};
+
+struct max14001_chip_info {

drivers/iio/adc/max14001.c new file +4 -0

+{
+	struct spi_transfer xfer[] = {
+		{
+			.tx_buf = &st->tx_buffer,

drivers/iio/adc/max14001.c new file +9 -0

+	st->tx_buffer = FIELD_PREP(MAX14001_MASK_ADDR, reg) |
+			FIELD_PREP(MAX14001_MASK_WR, MAX14001_REG_READ);
+	st->tx_buffer = bitrev16(st->tx_buffer);
+
+	ret = spi_sync_transfer(st->spi, xfer, ARRAY_SIZE(xfer));
+	if (ret < 0)
+		return ret;
+
+	st->rx_buffer = bitrev16(be16_to_cpu(st->rx_buffer));

drivers/iio/adc/max14001.c new file +11 -0

+};
+MODULE_DEVICE_TABLE(spi, max14001_id_table);
+
+static const struct of_device_id max14001_of_match[] = {
+	{ .compatible = "adi,max14001",
+	  .data = &max14001_chip_info_tbl[max14001], },
+	{ .compatible = "adi,max14002",
+	  .data = &max14001_chip_info_tbl[max14002], },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max14001_of_match);

Hello maintainers,

This patch series adds basic support for the Analog Devices MAX14001/MAX14002, configurable, isolated 10-bit ADCs for multi-range binary inputs. Besides the implemented ADC readings, these devices have more features, like a binary comparator; a filtered reading that can provide the average of the last 2, 4, or 8 ADC readings; and an inrush comparator that triggers the inrush current. There is also a fault feature that can diagnose seven possible fault conditions.

To keep the commits simple and organized, these initial driver support patches aim to upstream only the features related to reading two registers, one that contains the latest ADC reading, and another one that contains the latest filtered ADC readings. Though, _raw and _mean_raw are providing the same results in this initial version since the data averaging config interface is not implemented yet. For this, IIO_CHAN_INFO_AVERAGE_RAW was used to return the filtered average of ADC readings. An additional patch documenting the in_voltageY_mean_raw interface can be added on v2 if that would be desirable. The idea is to use in_voltageY_mean_raw to return the filtered average value, and also to set how many ADC readings (0, 2, 4, or 8) are included in the mean calculation. I would also like to know if you have any feedback on using IIO_CHAN_INFO_AVERAGE_RAW in this way.

The changes were tested using the Raspberry Pi modified kernel version rpi-6.6 on Raspberry Pi 5 hardware. For testing, the MAX14001PMB evaluation board was used, which contains two MAX14001 devices. According to the board’s circuit configuration, one device measures current and the other measures voltage. Due to the evaluation board’s circuitry, the devices also receive an offset that allows them to measure negative values. None of these evaluation board-specific characteristics were included in the driver code (neither the offset nor the current channel capability). However, they were considered in the calculation of the values read by the devices. Should the code that applies these board configuration parameters be added as an additional driver file inside the IIO subsystem, or should it remain only in a user application file?

The code was developed during the GSoC program as part of the Analog Devices Mentorship. Many thanks to my mentors Marcelo Schmitt, Ceclan Dumitru, Jonathan Santos and Dragos Bogdan for their guidance, reviews, and explanations about the IIO subsystem code.

I intend to keep sending patches to cover all the features of the device.

Quoted 4 lines · Marilene Andrade Garcia

Hello maintainers,

This patch series adds basic support for the Analog Devices MAX14001/MAX14002, configurable, isolated 10-bit ADCs for multi-range

Something gone wrong here? There's already a v9 from another ADI employee on the list:
https://lore.kernel.org/all/[email protected]/

Quoted 5 lines · Conor Dooley

Quoted 4 lines · Marilene Andrade Garcia

Hello maintainers,

This patch series adds basic support for the Analog Devices MAX14001/MAX14002, configurable, isolated 10-bit ADCs for multi-range

...

Quoted 4 lines

Something gone wrong here? There's already a v9 from another ADI employee on the list:
https://lore.kernel.org/all/[email protected]/

Yes, my procedure for finding parts for GSoC projects failed to find that set. From quick read of v9 thread, the reason for that not being applied was lack of detailed comments about device data transfer handling?
Anyway, I guess the only thing left to do now is see what can be taken from Marilene's set and applied on top of Kim's one.

I'm sorry for this unfortunate situation.