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iio: adc: ltc2378: Add support for LTC2378-20 and similar ADCs

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Support for LTC2378-20 and similar analog-to-digital converters.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
This commit is contained in:
Marcelo Schmitt 2026-07-27 18:30:54 -03:00 committed by Jonathan Cameron
parent 6c0e726821
commit 469eafdc69
4 changed files with 401 additions and 0 deletions
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1
MAINTAINERS
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@ -15349,6 +15349,7 @@ L: linux-iio@vger.kernel.org
S: Supported
W: https://ez.analog.com/linux-software-drivers
F: Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
F: drivers/iio/adc/ltc2378.c
LTC2664 IIO DAC DRIVER
M: Michael Hennerich <michael.hennerich@analog.com>

12
drivers/iio/adc/Kconfig
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@ -943,6 +943,18 @@ config LTC2309
This driver can also be built as a module. If so, the module will
be called ltc2309.
config LTC2378
tristate "Analog Devices LTC2378 ADC driver"
depends on SPI
depends on REGULATOR || COMPILE_TEST
depends on GPIOLIB
help
Say yes here to build support for Analog Devices LTC2378-20 and
similar analog to digital converters.
This driver can also be built as a module. If so, the module will
be called ltc2378.
config LTC2471
tristate "Linear Technology LTC2471 and LTC2473 ADC driver"
depends on I2C

1
drivers/iio/adc/Makefile
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@ -81,6 +81,7 @@ obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
obj-$(CONFIG_LPC18XX_ADC) += lpc18xx_adc.o
obj-$(CONFIG_LPC32XX_ADC) += lpc32xx_adc.o
obj-$(CONFIG_LTC2309) += ltc2309.o
obj-$(CONFIG_LTC2378) += ltc2378.o
obj-$(CONFIG_LTC2471) += ltc2471.o
obj-$(CONFIG_LTC2485) += ltc2485.o
obj-$(CONFIG_LTC2496) += ltc2496.o ltc2497-core.o

387
drivers/iio/adc/ltc2378.c Normal file
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@ -0,0 +1,387 @@
// SPDX-License-Identifier: GPL-2.0+
/*
* Analog Devices LTC2378 ADC series driver
*
* Copyright (C) 2026 Analog Devices Inc.
* Author: Marcelo Schmitt <marcelo.schmitt@analog.com>
*/
#include <linux/bitops.h>
#include <linux/bits.h>
#include <linux/byteorder/generic.h>
#include <linux/cleanup.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/device-id/spi.h>
#include <linux/device-id/of.h>
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/mutex.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>
#define LTC2378_MAX_DATA_WAIT_US 4 /* max(TBUSYLH + TCONV + TDSDOBUSYL) */
#define LTC2378_CHANNEL(_sign, _real_bits, _storage_bits) \
{ \
.type = IIO_VOLTAGE, \
.indexed = 1, \
.differential = _sign, \
.channel = 0, \
.channel2 = _sign ? 1 : 0, \
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
BIT(IIO_CHAN_INFO_SCALE), \
.scan_index = 0, \
.scan_type = { \
.format = _sign ? IIO_SCAN_FORMAT_SIGNED_INT : \
IIO_SCAN_FORMAT_UNSIGNED_INT, \
.realbits = _real_bits, \
.storagebits = _storage_bits, \
.shift = _storage_bits - _real_bits, \
.endianness = IIO_BE, \
}, \
}
#define LTC2378_DIFF_CHANNEL(_real_bits) \
LTC2378_CHANNEL(1, _real_bits, (((_real_bits) > 16) ? 32 : 16))
#define LTC2378_PSEUDO_DIFF_CHANNEL(_real_bits) \
LTC2378_CHANNEL(0, _real_bits, (((_real_bits) > 16) ? 32 : 16))
struct ltc2378_chip_info {
const char *name;
struct iio_chan_spec chan;
};
struct ltc2378_state {
const struct ltc2378_chip_info *info;
struct gpio_desc *cnv_gpio;
struct spi_device *spi;
struct mutex lock; /* Protect data acquisition cycle */
int ref_uV;
struct spi_transfer xfer;
/*
* DMA (thus cache coherency maintenance) requires the transfer buffers
* to live in their own cache lines.
*/
struct {
union {
__be16 sample_buf16_be;
__be32 sample_buf32_be;
u16 sample_buf16;
u32 sample_buf32;
} data;
aligned_s64 timestamp;
} scan __aligned(IIO_DMA_MINALIGN);
};
static const struct ltc2378_chip_info ltc2364_16_chip_info = {
.name = "ltc2364-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2364_18_chip_info = {
.name = "ltc2364-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2367_16_chip_info = {
.name = "ltc2367-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2367_18_chip_info = {
.name = "ltc2367-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2368_16_chip_info = {
.name = "ltc2368-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2368_18_chip_info = {
.name = "ltc2368-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2369_18_chip_info = {
.name = "ltc2369-18",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2370_16_chip_info = {
.name = "ltc2370-16",
.chan = LTC2378_PSEUDO_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2376_16_chip_info = {
.name = "ltc2376-16",
.chan = LTC2378_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2376_18_chip_info = {
.name = "ltc2376-18",
.chan = LTC2378_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2376_20_chip_info = {
.name = "ltc2376-20",
.chan = LTC2378_DIFF_CHANNEL(20),
};
static const struct ltc2378_chip_info ltc2377_16_chip_info = {
.name = "ltc2377-16",
.chan = LTC2378_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2377_18_chip_info = {
.name = "ltc2377-18",
.chan = LTC2378_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2377_20_chip_info = {
.name = "ltc2377-20",
.chan = LTC2378_DIFF_CHANNEL(20),
};
static const struct ltc2378_chip_info ltc2378_16_chip_info = {
.name = "ltc2378-16",
.chan = LTC2378_DIFF_CHANNEL(16),
};
static const struct ltc2378_chip_info ltc2378_18_chip_info = {
.name = "ltc2378-18",
.chan = LTC2378_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2378_20_chip_info = {
.name = "ltc2378-20",
.chan = LTC2378_DIFF_CHANNEL(20),
};
static const struct ltc2378_chip_info ltc2379_18_chip_info = {
.name = "ltc2379-18",
.chan = LTC2378_DIFF_CHANNEL(18),
};
static const struct ltc2378_chip_info ltc2380_16_chip_info = {
.name = "ltc2380-16",
.chan = LTC2378_DIFF_CHANNEL(16),
};
static int ltc2378_convert_and_acquire(struct ltc2378_state *st)
{
int ret;
/* Cause a rising edge of CNV to initiate a new ADC conversion */
gpiod_set_value_cansleep(st->cnv_gpio, 1);
fsleep(LTC2378_MAX_DATA_WAIT_US);
ret = spi_sync_transfer(st->spi, &st->xfer, 1);
gpiod_set_value_cansleep(st->cnv_gpio, 0);
return ret;
}
static int ltc2378_channel_single_read(const struct iio_chan_spec *chan,
struct ltc2378_state *st, int *val)
{
const struct iio_scan_type *scan_type = &chan->scan_type;
u32 sample;
int ret;
guard(mutex)(&st->lock);
ret = ltc2378_convert_and_acquire(st);
if (ret)
return ret;
if (chan->scan_type.endianness == IIO_BE) {
if (chan->scan_type.realbits > 16)
sample = be32_to_cpu(st->scan.data.sample_buf32_be);
else
sample = be16_to_cpu(st->scan.data.sample_buf16_be);
} else { /* IIO_CPU */
if (chan->scan_type.realbits > 16)
sample = st->scan.data.sample_buf32;
else
sample = st->scan.data.sample_buf16;
}
sample >>= chan->scan_type.shift;
if (scan_type->format == IIO_SCAN_FORMAT_SIGNED_INT)
*val = sign_extend32(sample, scan_type->realbits - 1);
else
*val = sample;
return 0;
}
static int ltc2378_read_raw(struct iio_dev *indio_dev,
const struct iio_chan_spec *chan,
int *val, int *val2, long mask)
{
struct ltc2378_state *st = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_RAW: {
IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
if (IIO_DEV_ACQUIRE_FAILED(claim))
return -EBUSY;
ret = ltc2378_channel_single_read(chan, st, val);
if (ret)
return ret;
return IIO_VAL_INT;
}
case IIO_CHAN_INFO_SCALE:
*val = st->ref_uV / MILLI;
/*
* For all LTC2378-like devices, the amount of bits that express
* voltage magnitude depend on the polarity / output code format:
* - straight binary: All precision/resolution bits are used.
* - 2's complement: One of the precision bits is used for sign.
*/
if (chan->scan_type.format == IIO_SCAN_FORMAT_SIGNED_INT)
*val2 = chan->scan_type.realbits - 1;
else
*val2 = chan->scan_type.realbits;
return IIO_VAL_FRACTIONAL_LOG2;
default:
return -EINVAL;
}
}
static const struct iio_info ltc2378_iio_info = {
.read_raw = &ltc2378_read_raw,
};
static int ltc2378_ref_setup(struct device *dev, struct ltc2378_state *st)
{
int ret;
ret = devm_regulator_get_enable_read_voltage(dev, "ref");
if (ret < 0)
return dev_err_probe(dev, ret, "failed to read ref regulator\n");
st->ref_uV = ret;
return 0;
}
static int ltc2378_probe(struct spi_device *spi)
{
struct device *dev = &spi->dev;
struct iio_dev *indio_dev;
struct ltc2378_state *st;
int ret;
indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
if (!indio_dev)
return -ENOMEM;
st = iio_priv(indio_dev);
st->spi = spi;
ret = devm_mutex_init(dev, &st->lock);
if (ret)
return ret;
st->info = spi_get_device_match_data(spi);
if (!st->info)
return -EINVAL;
ret = ltc2378_ref_setup(dev, st);
if (ret)
return ret;
indio_dev->name = st->info->name;
indio_dev->info = &ltc2378_iio_info;
indio_dev->modes = INDIO_DIRECT_MODE;
st->cnv_gpio = devm_gpiod_get(dev, "cnv", GPIOD_OUT_LOW);
if (IS_ERR(st->cnv_gpio))
return dev_err_probe(dev, PTR_ERR(st->cnv_gpio),
"failed to get CNV GPIO");
indio_dev->channels = &st->info->chan;
indio_dev->num_channels = 1;
st->xfer.rx_buf = &st->scan.data;
st->xfer.len = spi_bpw_to_bytes(indio_dev->channels[0].scan_type.realbits);
return devm_iio_device_register(&spi->dev, indio_dev);
}
static const struct of_device_id ltc2378_of_match[] = {
{ .compatible = "adi,ltc2364-16", .data = &ltc2364_16_chip_info },
{ .compatible = "adi,ltc2364-18", .data = &ltc2364_18_chip_info },
{ .compatible = "adi,ltc2367-16", .data = &ltc2367_16_chip_info },
{ .compatible = "adi,ltc2367-18", .data = &ltc2367_18_chip_info },
{ .compatible = "adi,ltc2368-16", .data = &ltc2368_16_chip_info },
{ .compatible = "adi,ltc2368-18", .data = &ltc2368_18_chip_info },
{ .compatible = "adi,ltc2369-18", .data = &ltc2369_18_chip_info },
{ .compatible = "adi,ltc2370-16", .data = &ltc2370_16_chip_info },
{ .compatible = "adi,ltc2376-16", .data = &ltc2376_16_chip_info },
{ .compatible = "adi,ltc2376-18", .data = &ltc2376_18_chip_info },
{ .compatible = "adi,ltc2376-20", .data = &ltc2376_20_chip_info },
{ .compatible = "adi,ltc2377-16", .data = &ltc2377_16_chip_info },
{ .compatible = "adi,ltc2377-18", .data = &ltc2377_18_chip_info },
{ .compatible = "adi,ltc2377-20", .data = &ltc2377_20_chip_info },
{ .compatible = "adi,ltc2378-16", .data = &ltc2378_16_chip_info },
{ .compatible = "adi,ltc2378-18", .data = &ltc2378_18_chip_info },
{ .compatible = "adi,ltc2378-20", .data = &ltc2378_20_chip_info },
{ .compatible = "adi,ltc2379-18", .data = &ltc2379_18_chip_info },
{ .compatible = "adi,ltc2380-16", .data = &ltc2380_16_chip_info },
{ }
};
MODULE_DEVICE_TABLE(of, ltc2378_of_match);
static const struct spi_device_id ltc2378_spi_id[] = {
{ .name = "ltc2364-16", .driver_data = (kernel_ulong_t)&ltc2364_16_chip_info },
{ .name = "ltc2364-18", .driver_data = (kernel_ulong_t)&ltc2364_18_chip_info },
{ .name = "ltc2367-16", .driver_data = (kernel_ulong_t)&ltc2367_16_chip_info },
{ .name = "ltc2367-18", .driver_data = (kernel_ulong_t)&ltc2367_18_chip_info },
{ .name = "ltc2368-16", .driver_data = (kernel_ulong_t)&ltc2368_16_chip_info },
{ .name = "ltc2368-18", .driver_data = (kernel_ulong_t)&ltc2368_18_chip_info },
{ .name = "ltc2369-18", .driver_data = (kernel_ulong_t)&ltc2369_18_chip_info },
{ .name = "ltc2370-16", .driver_data = (kernel_ulong_t)&ltc2370_16_chip_info },
{ .name = "ltc2376-16", .driver_data = (kernel_ulong_t)&ltc2376_16_chip_info },
{ .name = "ltc2376-18", .driver_data = (kernel_ulong_t)&ltc2376_18_chip_info },
{ .name = "ltc2376-20", .driver_data = (kernel_ulong_t)&ltc2376_20_chip_info },
{ .name = "ltc2377-16", .driver_data = (kernel_ulong_t)&ltc2377_16_chip_info },
{ .name = "ltc2377-18", .driver_data = (kernel_ulong_t)&ltc2377_18_chip_info },
{ .name = "ltc2377-20", .driver_data = (kernel_ulong_t)&ltc2377_20_chip_info },
{ .name = "ltc2378-16", .driver_data = (kernel_ulong_t)&ltc2378_16_chip_info },
{ .name = "ltc2378-18", .driver_data = (kernel_ulong_t)&ltc2378_18_chip_info },
{ .name = "ltc2378-20", .driver_data = (kernel_ulong_t)&ltc2378_20_chip_info },
{ .name = "ltc2379-18", .driver_data = (kernel_ulong_t)&ltc2379_18_chip_info },
{ .name = "ltc2380-16", .driver_data = (kernel_ulong_t)&ltc2380_16_chip_info },
{ }
};
MODULE_DEVICE_TABLE(spi, ltc2378_spi_id);
static struct spi_driver ltc2378_driver = {
.driver = {
.name = "ltc2378",
.of_match_table = ltc2378_of_match
},
.probe = ltc2378_probe,
.id_table = ltc2378_spi_id,
};
module_spi_driver(ltc2378_driver);
MODULE_AUTHOR("Marcelo Schmitt <marcelo.schmitt@analog.com>");
MODULE_DESCRIPTION("Analog Devices LTC2378 ADC series driver");
MODULE_LICENSE("GPL");