[PATCH v11 2/3] iio: adc: max14001: New driver

Marilene Andrade Garcia
2025-09-15T22:16:42Z

The MAX14001/MAX14002 is configurable, isolated 10-bit ADCs for multi-range
binary inputs. In addition to 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.

MAX14001/MAX14002 features implemented so far:
- Raw ADC reading.
- Filtered ADC average reading with the default configuration.
- MV fault disable.
- Selection of external or internal ADC voltage reference, depending on
whether it is declared in the device tree.

Co-developed-by: Kim Seer Paller <kimseer.paller@analog.com>
Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
Signed-off-by: Marilene Andrade Garcia <marilene.agarcia@gmail.com>
---

I have addressed almost all of the comments, thank you very much for the
review. I would like to highlight some of them:

Changes since v10:
- Dropped the kernel.h include
- Add the cleanup.h, mutex.h, regmap.h and units.h includes
- Renamed the reg_addr variable name to reg
- Renamed the reg_data variable name to val
- Added the regmap implementation
- Used scoped_guard()
- Refactored the get refin voltage code
- Replace max14001_chip_model with data structures separated
- Added debugfs_reg_access

Change I was not able to do:
- I could not remove bitrev16 because I am using an SPI controller that
does not support SPI_LSB_FIRST. So I suggest keeping bitrev16 and not using
the spi-lsb-first devicetree property for now, since this driver currently
works for both types of controllers: those that support it and those that
do not. I left a TODO comment to address this issue as soon as the SPI
kernel code starts handling the bit-reverse operation for controllers that
do not have this support. Once I finish my work on this driver, if the SPI
code still does not include this handling, I can submit patches to add it.

MAINTAINERS | 1 +
drivers/iio/adc/Kconfig | 10 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/max14001.c | 356 +++++++++++++++++++++++++++++++++++++
4 files changed, 368 insertions(+)
create mode 100644 drivers/iio/adc/max14001.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 0bae420caa63..a9cf93ba8b21 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14998,6 +14998,7 @@ L: linux-iio@vger.kernel.org
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

MAXBOTIX ULTRASONIC RANGER IIO DRIVER
M: Andreas Klinger <ak@it-klinger.de>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 237fa2061329..a1f2afce60ad 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -991,6 +991,16 @@ config MAX11410
To compile this driver as a module, choose M here: the module will be
called max11410.

+config MAX14001
+ tristate "Analog Devices MAX14001/MAX14002 ADC 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 MAX1241
tristate "Maxim max1241 ADC driver"
depends on SPI_MASTER
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 611c16430621..9c4ceb527db7 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -87,6 +87,7 @@ obj-$(CONFIG_MAX11100) += max11100.o
obj-$(CONFIG_MAX1118) += max1118.o
obj-$(CONFIG_MAX11205) += max11205.o
obj-$(CONFIG_MAX11410) += max11410.o
+obj-$(CONFIG_MAX14001) += max14001.o
obj-$(CONFIG_MAX1241) += max1241.o
obj-$(CONFIG_MAX1363) += max1363.o
obj-$(CONFIG_MAX34408) += max34408.o
diff --git a/drivers/iio/adc/max14001.c b/drivers/iio/adc/max14001.c
new file mode 100644
index 000000000000..2ade57970064
--- /dev/null
+++ b/drivers/iio/adc/max14001.c
@@ -0,0 +1,356 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+/*
+ * Analog Devices MAX14001/MAX14002 ADC driver
+ *
+ * Copyright (C) 2023-2025 Analog Devices Inc.
+ * Copyright (C) 2023 Kim Seer Paller <kimseer.paller@analog.com>
+ * Copyright (c) 2025 Marilene Andrade Garcia <marilene.agarcia@gmail.com>
+ *
+ * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/MAX14001-MAX14002.pdf
+ */
+
+/*
+ * TODO:
+ * Replace bitrev16 with SPI_LSB_FIRST once the SPI kernel code supports handling
+ * SPI controllers that lack LSB-first support.
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitfield.h>
+#include <linux/bitrev.h>
+#include <linux/bits.h>
+#include <linux/byteorder/generic.h>
+#include <linux/cleanup.h>
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+/* MAX14001 Registers Address */
+#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
+#define MAX14001_REG_THU 0x05
+#define MAX14001_REG_INRR 0x06
+#define MAX14001_REG_INRT 0x07
+#define MAX14001_REG_INRP 0x08
+#define MAX14001_REG_CFG 0x09
+#define MAX14001_REG_ENBL 0x0A
+#define MAX14001_REG_ACT 0x0B
+#define MAX14001_REG_WEN 0x0C
+
+#define MAX14001_REG_VERIFICATION(x) ((x) + 0x10)
+
+#define MAX14001_REG_CFG_BIT_EXRF BIT(5)
+
+#define MAX14001_REG_WEN_VALUE_WRITE 0x294
+
+#define MAX14001_MASK_ADDR GENMASK(15, 11)
+#define MAX14001_MASK_WR BIT(10)
+#define MAX14001_MASK_DATA GENMASK(9, 0)
+
+struct max14001_state {
+ const struct max14001_chip_info *chip_info;
+ struct spi_device *spi;
+ struct regmap *regmap;
+ int vref_mV;
+ /*
+ * lock protect against multiple concurrent accesses, RMW sequence,
+ * and SPI transfer.
+ */
+ struct mutex lock;
+ /*
+ * The following buffers will be bit-reversed during device
+ * communication, because the device transmits and receives data
+ * LSB-first.
+ * DMA (thus cache coherency maintenance) requires the transfer
+ * buffers to live in their own cache lines.
+ */
+ __be16 spi_tx_buffer __aligned(IIO_DMA_MINALIGN);
+ __be16 spi_rx_buffer;
+};
+
+struct max14001_chip_info {
+ const char *name;
+};
+
+static struct max14001_chip_info max14001_chip_info = {
+ .name = "max14001",
+};
+
+static struct max14001_chip_info max14002_chip_info = {
+ .name = "max14002",
+};
+
+static int max14001_read(void *context, unsigned int reg, unsigned int *val)
+{
+ struct max14001_state *st = context;
+ struct spi_transfer xfers[] = {
+ {
+ .tx_buf = &st->spi_tx_buffer,
+ .len = sizeof(st->spi_tx_buffer),
+ .cs_change = 1,
+ }, {
+ .rx_buf = &st->spi_rx_buffer,
+ .len = sizeof(st->spi_rx_buffer),
+ },
+ };
+ int ret;
+
+ /*
+ * Prepare SPI transmit buffer 16 bit-value big-endian format and
+ * reverses bit order to align with the LSB-first input on SDI port
+ * in order to meet the device communication requirements.
+ */
+ st->spi_tx_buffer = cpu_to_be16(bitrev16(FIELD_PREP(MAX14001_MASK_ADDR, reg)));
+
+ ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
+ if (ret)
+ return ret;
+
+ /*
+ * Convert received 16-bit value from big-endian to cpu-endian format
+ * and reverses bit order.
+ */
+ *val = FIELD_GET(MAX14001_MASK_DATA, bitrev16(be16_to_cpu(st->spi_rx_buffer)));
+
+ return 0;
+}
+
+static int max14001_write(struct max14001_state *st, unsigned int reg, unsigned int val)
+{
+ /*
+ * Prepare SPI transmit buffer 16 bit-value big-endian format and
+ * reverses bit order to align with the LSB-first input on SDI port
+ * in order to meet the device communication requirements.
+ */
+ st->spi_tx_buffer = cpu_to_be16(bitrev16(FIELD_PREP(MAX14001_MASK_ADDR, reg) |
+ FIELD_PREP(MAX14001_MASK_WR, 1) |
+ FIELD_PREP(MAX14001_MASK_DATA, val)));
+
+ return spi_write(st->spi, &st->spi_tx_buffer, sizeof(st->spi_tx_buffer));
+}
+
+static int max14001_write_single_reg(void *context, unsigned int reg, unsigned int val)
+{
+ struct max14001_state *st = context;
+ int ret;
+
+ /* Enable writing to the SPI register */
+ ret = max14001_write(st, MAX14001_REG_WEN, MAX14001_REG_WEN_VALUE_WRITE);
+ if (ret)
+ return ret;
+
+ /* Writing data into SPI register */
+ ret = max14001_write(st, reg, val);
+ if (ret)
+ return ret;
+
+ /* Disable writing to the SPI register */
+ return max14001_write(st, MAX14001_REG_WEN, 0);
+}
+
+static int max14001_write_verification_reg(struct max14001_state *st, unsigned int reg)
+{
+ unsigned int val;
+ int ret;
+
+ ret = regmap_read(st->regmap, reg, &val);
+ if (ret)
+ return ret;
+
+ return max14001_write(st, MAX14001_REG_VERIFICATION(reg), val);
+}
+
+static int max14001_disable_mv_fault(struct max14001_state *st)
+{
+ unsigned int reg;
+ int ret;
+
+ /* Enable writing to the SPI registers */
+ ret = max14001_write(st, MAX14001_REG_WEN, MAX14001_REG_WEN_VALUE_WRITE);
+ if (ret)
+ return ret;
+
+ /*
+ * Reads all registers and writes the values to their appropriate
+ * verification registers to clear the Memory Validation fault.
+ */
+ for (reg = MAX14001_REG_FLTEN; reg <= MAX14001_REG_ENBL; reg++) {
+ ret = max14001_write_verification_reg(st, reg);
+ if (ret)
+ return ret;
+ }
+
+ /* Disable writing to the SPI registers */
+ return max14001_write(st, MAX14001_REG_WEN, 0);
+}
+
+static int max14001_debugfs_reg_access(struct iio_dev *indio_dev,
+ unsigned int reg, unsigned int writeval,
+ unsigned int *readval)
+{
+ struct max14001_state *st = iio_priv(indio_dev);
+
+ if (readval)
+ return regmap_read(st->regmap, reg, readval);
+
+ return regmap_write(st->regmap, reg, writeval);
+}
+
+static int max14001_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct max14001_state *st = iio_priv(indio_dev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ scoped_guard(mutex, &st->lock)
+ ret = regmap_read(st->regmap, MAX14001_REG_ADC, val);
+ if (ret)
+ return ret;
+
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_AVERAGE_RAW:
+ scoped_guard(mutex, &st->lock)
+ ret = regmap_read(st->regmap, MAX14001_REG_FADC, val);
+ if (ret)
+ return ret;
+
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = st->vref_mV;
+ *val2 = 10;
+
+ return IIO_VAL_FRACTIONAL_LOG2;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct regmap_config max14001_regmap_config = {
+ .reg_read = max14001_read,
+ .reg_write = max14001_write_single_reg,
+};
+
+static const struct iio_info max14001_info = {
+ .read_raw = max14001_read_raw,
+ .debugfs_reg_access = max14001_debugfs_reg_access,
+};
+
+static const struct iio_chan_spec max14001_channel[] = {
+ {
+ .type = IIO_VOLTAGE,
+ .indexed = 1,
+ .channel = 0,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_AVERAGE_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ },
+};
+
+static int max14001_probe(struct spi_device *spi)
+{
+ struct device *dev = &spi->dev;
+ struct iio_dev *indio_dev;
+ struct max14001_state *st;
+ int ret, ext_vrefin = 0;
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ st = iio_priv(indio_dev);
+ st->spi = spi;
+ st->chip_info = spi_get_device_match_data(spi);
+ if (!st->chip_info)
+ return dev_err_probe(dev, -ENODEV, "Failed to get match data\n");
+
+ indio_dev->name = st->chip_info->name;
+ indio_dev->info = &max14001_info;
+ indio_dev->channels = max14001_channel;
+ indio_dev->num_channels = ARRAY_SIZE(max14001_channel);
+ indio_dev->modes = INDIO_DIRECT_MODE;
+
+ st->regmap = devm_regmap_init(dev, NULL, st, &max14001_regmap_config);
+ if (IS_ERR(st->regmap))
+ return dev_err_probe(dev, PTR_ERR(st->regmap), "Failed to initialize regmap\n");
+
+ ret = devm_mutex_init(dev, &st->lock);
+ if (ret)
+ return ret;
+
+ ret = devm_regulator_get_enable(dev, "vdd");
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to enable Vdd supply\n");
+
+ ret = devm_regulator_get_enable(dev, "vddl");
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to enable Vddl supply\n");
+
+ ret = devm_regulator_get_enable_read_voltage(dev, "refin");
+ if (ret < 0 && ret != -ENODEV)
+ return dev_err_probe(dev, ret, "Failed to get REFIN voltage\n");
+
+ if (ret < 0)
+ ret = 1250000;
+ else
+ ext_vrefin = 1;
+ st->vref_mV = ret / (MICRO / MILLI);
+
+ if (ext_vrefin) {
+ /*
+ * Configure the MAX14001/MAX14002 to use an external voltage reference source
+ * by setting the bit 5 of the configuration register
+ */
+ ret = regmap_update_bits(st->regmap, MAX14001_REG_CFG, MAX14001_REG_CFG_BIT_EXRF, MAX14001_REG_CFG_BIT_EXRF);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to set External REFIN in Configuration Register\n");
+ }
+
+ ret = max14001_disable_mv_fault(st);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to disable MV Fault\n");
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct spi_device_id max14001_id_table[] = {
+ { "max14001", (kernel_ulong_t)&max14001_chip_info },
+ { "max14002", (kernel_ulong_t)&max14002_chip_info },
+ { }
+};
+
+static const struct of_device_id max14001_of_match[] = {
+ { .compatible = "adi,max14001", .data = &max14001_chip_info },
+ { .compatible = "adi,max14002", .data = &max14002_chip_info },
+ { }
+};
+MODULE_DEVICE_TABLE(of, max14001_of_match);
+
+static struct spi_driver max14001_driver = {
+ .driver = {
+ .name = "max14001",
+ .of_match_table = max14001_of_match,
+ },
+ .probe = max14001_probe,
+ .id_table = max14001_id_table,
+};
+module_spi_driver(max14001_driver);
+
+MODULE_AUTHOR("Kim Seer Paller <kimseer.paller@analog.com>");
+MODULE_AUTHOR("Marilene Andrade Garcia <marilene.agarcia@gmail.com>");
+MODULE_DESCRIPTION("Analog Devices MAX14001/MAX14002 ADCs driver");
+MODULE_LICENSE("GPL");
--
2.34.1