[PATCH v6 2/3] iio: adc: ad7191: add AD7191

Alisa-Dariana Roman
2025-02-28T14:13:54Z

AD7191 is a pin-programmable, ultra-low noise 24-bit sigma-delta ADC
designed for precision bridge sensor measurements. It features two
differential analog input channels, selectable output rates,
programmable gain, internal temperature sensor and simultaneous
50Hz/60Hz rejection.

Signed-off-by: Alisa-Dariana Roman <alisa.roman@analog.com>
---
MAINTAINERS | 1 +
drivers/iio/adc/Kconfig | 10 +
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ad7191.c | 554 +++++++++++++++++++++++++++++++++++++++
4 files changed, 566 insertions(+)
create mode 100644 drivers/iio/adc/ad7191.c

diff --git a/MAINTAINERS b/MAINTAINERS
index ac1f61256932..87c491975ced 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1352,6 +1352,7 @@ L: linux-iio@vger.kernel.org
S: Supported
W: https://ez.analog.com/linux-software-drivers
F: Documentation/devicetree/bindings/iio/adc/adi,ad7191.yaml
+F: drivers/iio/adc/ad7191.c

ANALOG DEVICES INC AD7192 DRIVER
M: Alisa-Dariana Roman <alisa.roman@analog.com>
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 27413516216c..b7ae6e0ae0df 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -142,6 +142,16 @@ config AD7173
To compile this driver as a module, choose M here: the module will be
called ad7173.

+config AD7191
+ tristate "Analog Devices AD7191 ADC driver"
+ depends on SPI
+ select AD_SIGMA_DELTA
+ help
+ Say yes here to build support for Analog Devices AD7191.
+
+ To compile this driver as a module, choose M here: the
+ module will be called ad7191.
+
config AD7192
tristate "Analog Devices AD7192 and similar ADC driver"
depends on SPI
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 9f26d5eca822..3e918c3eec69 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_AD7091R5) += ad7091r5.o
obj-$(CONFIG_AD7091R8) += ad7091r8.o
obj-$(CONFIG_AD7124) += ad7124.o
obj-$(CONFIG_AD7173) += ad7173.o
+obj-$(CONFIG_AD7191) += ad7191.o
obj-$(CONFIG_AD7192) += ad7192.o
obj-$(CONFIG_AD7266) += ad7266.o
obj-$(CONFIG_AD7280) += ad7280a.o
diff --git a/drivers/iio/adc/ad7191.c b/drivers/iio/adc/ad7191.c
new file mode 100644
index 000000000000..d9cd903ffdd2
--- /dev/null
+++ b/drivers/iio/adc/ad7191.c
@@ -0,0 +1,554 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AD7191 ADC driver
+ *
+ * Copyright 2025 Analog Devices Inc.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/interrupt.h>
+#include <linux/mod_devicetable.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#include <linux/iio/adc/ad_sigma_delta.h>
+#include <linux/iio/iio.h>
+
+#define ad_sigma_delta_to_ad7191(sigmad) \
+ container_of((sigmad), struct ad7191_state, sd)
+
+#define AD7191_TEMP_CODES_PER_DEGREE 2815
+
+#define AD7191_CHAN_MASK BIT(0)
+#define AD7191_TEMP_MASK BIT(1)
+
+enum ad7191_channel {
+ AD7191_CH_AIN1_AIN2,
+ AD7191_CH_AIN3_AIN4,
+ AD7191_CH_TEMP,
+};
+
+/*
+ * NOTE:
+ * The AD7191 features a dual-use data out ready DOUT/RDY output.
+ * In order to avoid contentions on the SPI bus, it's therefore necessary
+ * to use SPI bus locking.
+ *
+ * The DOUT/RDY output must also be wired to an interrupt-capable GPIO.
+ *
+ * The SPI controller's chip select must be connected to the PDOWN pin
+ * of the ADC. When CS (PDOWN) is high, it powers down the device and
+ * resets the internal circuitry.
+ */
+
+struct ad7191_state {
+ struct ad_sigma_delta sd;
+ struct mutex lock; /* Protect device state */
+
+ struct gpio_descs *odr_gpios;
+ struct gpio_descs *pga_gpios;
+ struct gpio_desc *temp_gpio;
+ struct gpio_desc *chan_gpio;
+
+ u16 int_vref_mv;
+ const u32 (*scale_avail)[2];
+ size_t scale_avail_size;
+ u32 scale_index;
+ const u32 *samp_freq_avail;
+ size_t samp_freq_avail_size;
+ u32 samp_freq_index;
+
+ struct clk *mclk;
+};
+
+static int ad7191_set_channel(struct ad_sigma_delta *sd, unsigned int address)
+{
+ struct ad7191_state *st = ad_sigma_delta_to_ad7191(sd);
+ u8 temp_gpio_val, chan_gpio_val;
+
+ if (!FIELD_FIT(AD7191_CHAN_MASK | AD7191_TEMP_MASK, address))
+ return -EINVAL;
+
+ chan_gpio_val = FIELD_GET(AD7191_CHAN_MASK, address);
+ temp_gpio_val = FIELD_GET(AD7191_TEMP_MASK, address);
+
+ gpiod_set_value(st->chan_gpio, chan_gpio_val);
+ gpiod_set_value(st->temp_gpio, temp_gpio_val);
+
+ return 0;
+}
+
+static int ad7191_set_cs(struct ad_sigma_delta *sigma_delta, int assert)
+{
+ struct spi_transfer t = {
+ .len = 0,
+ .cs_change = assert,
+ };
+ struct spi_message m;
+
+ spi_message_init_with_transfers(&m, &t, 1);
+
+ return spi_sync_locked(sigma_delta->spi, &m);
+}
+
+static int ad7191_set_mode(struct ad_sigma_delta *sd,
+ enum ad_sigma_delta_mode mode)
+{
+ struct ad7191_state *st = ad_sigma_delta_to_ad7191(sd);
+
+ switch (mode) {
+ case AD_SD_MODE_CONTINUOUS:
+ case AD_SD_MODE_SINGLE:
+ return ad7191_set_cs(&st->sd, 1);
+ case AD_SD_MODE_IDLE:
+ return ad7191_set_cs(&st->sd, 0);
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct ad_sigma_delta_info ad7191_sigma_delta_info = {
+ .set_channel = ad7191_set_channel,
+ .set_mode = ad7191_set_mode,
+ .has_registers = false,
+};
+
+static int ad7191_init_regulators(struct iio_dev *indio_dev)
+{
+ struct ad7191_state *st = iio_priv(indio_dev);
+ struct device *dev = &st->sd.spi->dev;
+ int ret;
+
+ ret = devm_regulator_get_enable(dev, "avdd");
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to enable specified AVdd supply\n");
+
+ ret = devm_regulator_get_enable(dev, "dvdd");
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to enable specified DVdd supply\n");
+
+ ret = devm_regulator_get_enable_read_voltage(dev, "vref");
+ if (ret < 0)
+ return dev_err_probe(dev, ret, "Failed to get Vref voltage\n");
+
+ st->int_vref_mv = ret / 1000;
+
+ return 0;
+}
+
+static int ad7191_config_setup(struct iio_dev *indio_dev)
+{
+ struct ad7191_state *st = iio_priv(indio_dev);
+ struct device *dev = &st->sd.spi->dev;
+ /* Sampling frequencies in Hz, see Table 5 */
+ static const u32 samp_freq[4] = { 120, 60, 50, 10 };
+ /* Gain options, see Table 7 */
+ const u32 gain[4] = { 1, 8, 64, 128 };
+ static u32 scale_buffer[4][2];
+ int odr_value, odr_index = 0, pga_value, pga_index = 0, i, ret;
+ u64 scale_uv;
+
+ st->samp_freq_index = 0;
+ st->scale_index = 0;
+
+ ret = device_property_read_u32(dev, "adi,odr-value", &odr_value);
+ if (ret && ret != -EINVAL)
+ return dev_err_probe(dev, ret, "Failed to get odr value.\n");
+
+ if (ret == -EINVAL) {
+ st->odr_gpios = devm_gpiod_get_array(dev, "odr", GPIOD_OUT_LOW);
+ if (IS_ERR(st->odr_gpios))
+ return dev_err_probe(dev, PTR_ERR(st->odr_gpios),
+ "Failed to get odr gpios.\n");
+
+ if (st->odr_gpios->ndescs != 2)
+ return dev_err_probe(dev, -EINVAL, "Expected 2 odr gpio pins.\n");
+
+ st->samp_freq_avail = samp_freq;
+ st->samp_freq_avail_size = ARRAY_SIZE(samp_freq);
+ } else {
+ for (i = 0; i < ARRAY_SIZE(samp_freq); i++) {
+ if (odr_value != samp_freq[i])
+ continue;
+ odr_index = i;
+ break;
+ }
+
+ st->samp_freq_avail = &samp_freq[odr_index];
+ st->samp_freq_avail_size = 1;
+
+ st->odr_gpios = NULL;
+ }
+
+ mutex_lock(&st->lock);
+
+ for (i = 0; i < ARRAY_SIZE(scale_buffer); i++) {
+ scale_uv = ((u64)st->int_vref_mv * NANO) >>
+ (indio_dev->channels[0].scan_type.realbits - 1);
+ do_div(scale_uv, gain[i]);
+ scale_buffer[i][1] = do_div(scale_uv, NANO);
+ scale_buffer[i][0] = scale_uv;
+ }
+
+ mutex_unlock(&st->lock);
+
+ ret = device_property_read_u32(dev, "adi,pga-value", &pga_value);
+ if (ret && ret != -EINVAL)
+ return dev_err_probe(dev, ret, "Failed to get pga value.\n");
+
+ if (ret == -EINVAL) {
+ st->pga_gpios = devm_gpiod_get_array(dev, "pga", GPIOD_OUT_LOW);
+ if (IS_ERR(st->pga_gpios))
+ return dev_err_probe(dev, PTR_ERR(st->pga_gpios),
+ "Failed to get pga gpios.\n");
+
+ if (st->pga_gpios->ndescs != 2)
+ return dev_err_probe(dev, -EINVAL, "Expected 2 pga gpio pins.\n");
+
+ st->scale_avail = scale_buffer;
+ st->scale_avail_size = ARRAY_SIZE(scale_buffer);
+ } else {
+ for (i = 0; i < ARRAY_SIZE(gain); i++) {
+ if (pga_value != gain[i])
+ continue;
+ pga_index = i;
+ break;
+ }
+
+ st->scale_avail = &scale_buffer[pga_index];
+ st->scale_avail_size = 1;
+
+ st->pga_gpios = NULL;
+ }
+
+ st->temp_gpio = devm_gpiod_get(dev, "temp", GPIOD_OUT_LOW);
+ if (IS_ERR(st->temp_gpio))
+ return dev_err_probe(dev, PTR_ERR(st->temp_gpio),
+ "Failed to get temp gpio.\n");
+
+ st->chan_gpio = devm_gpiod_get(dev, "chan", GPIOD_OUT_LOW);
+ if (IS_ERR(st->chan_gpio))
+ return dev_err_probe(dev, PTR_ERR(st->chan_gpio),
+ "Failed to get chan gpio.\n");
+
+ return 0;
+}
+
+static int ad7191_clock_setup(struct ad7191_state *st)
+{
+ struct device *dev = &st->sd.spi->dev;
+
+ st->mclk = devm_clk_get_optional_enabled(dev, "mclk");
+ if (IS_ERR(st->mclk))
+ return dev_err_probe(dev, PTR_ERR(st->mclk),
+ "Failed to get mclk.\n");
+
+ return 0;
+}
+
+static int ad7191_setup(struct iio_dev *indio_dev)
+{
+ struct ad7191_state *st = iio_priv(indio_dev);
+ int ret;
+
+ ret = ad7191_init_regulators(indio_dev);
+ if (ret)
+ return ret;
+
+ ret = ad7191_config_setup(indio_dev);
+ if (ret)
+ return ret;
+
+ return ad7191_clock_setup(st);
+}
+
+static int ad7191_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long m)
+{
+ struct ad7191_state *st = iio_priv(indio_dev);
+
+ switch (m) {
+ case IIO_CHAN_INFO_RAW:
+ return ad_sigma_delta_single_conversion(indio_dev, chan, val);
+ case IIO_CHAN_INFO_SCALE:
+ switch (chan->type) {
+ case IIO_VOLTAGE: {
+ guard(mutex)(&st->lock);
+ *val = st->scale_avail[st->scale_index][0];
+ *val2 = st->scale_avail[st->scale_index][1];
+ return IIO_VAL_INT_PLUS_NANO;
+ }
+ case IIO_TEMP:
+ *val = 0;
+ *val2 = NANO / AD7191_TEMP_CODES_PER_DEGREE;
+ return IIO_VAL_INT_PLUS_NANO;
+ default:
+ return -EINVAL;
+ }
+ case IIO_CHAN_INFO_OFFSET:
+ *val = -(1 << (chan->scan_type.realbits - 1));
+ switch (chan->type) {
+ case IIO_VOLTAGE:
+ return IIO_VAL_INT;
+ case IIO_TEMP:
+ *val -= 273 * AD7191_TEMP_CODES_PER_DEGREE;
+ return IIO_VAL_INT;
+ default:
+ return -EINVAL;
+ }
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ *val = st->samp_freq_avail[st->samp_freq_index];
+ return IIO_VAL_INT;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad7191_set_gain(struct ad7191_state *st, int gain_index)
+{
+ DECLARE_BITMAP(bitmap, 2) = { };
+
+ st->scale_index = gain_index;
+
+ bitmap_write(bitmap, gain_index, 0, 2);
+
+ return gpiod_multi_set_value_cansleep(st->pga_gpios, bitmap);
+}
+
+static int ad7191_set_samp_freq(struct ad7191_state *st, int samp_freq_index)
+{
+ DECLARE_BITMAP(bitmap, 2) = {};
+
+ st->samp_freq_index = samp_freq_index;
+
+ bitmap_write(bitmap, samp_freq_index, 0, 2);
+
+ return gpiod_multi_set_value_cansleep(st->odr_gpios, bitmap);
+}
+
+static int __ad7191_write_raw(struct ad7191_state *st,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ int i;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE: {
+ if (!st->pga_gpios)
+ return -EPERM;
+ guard(mutex)(&st->lock);
+ for (i = 0; i < st->scale_avail_size; i++) {
+ if (val2 == st->scale_avail[i][1])
+ return ad7191_set_gain(st, i);
+ }
+ return -EINVAL;
+ }
+ case IIO_CHAN_INFO_SAMP_FREQ: {
+ if (!st->odr_gpios)
+ return -EPERM;
+ guard(mutex)(&st->lock);
+ for (i = 0; i < st->samp_freq_avail_size; i++) {
+ if (val == st->samp_freq_avail[i])
+ return ad7191_set_samp_freq(st, i);
+ }
+ return -EINVAL;
+ }
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad7191_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int val, int val2,
+ long mask)
+{
+ struct ad7191_state *st = iio_priv(indio_dev);
+ int ret;
+
+ if (!iio_device_claim_direct(indio_dev))
+ return -EBUSY;
+
+ ret = __ad7191_write_raw(st, chan, val, val2, mask);
+
+ iio_device_release_direct(indio_dev);
+
+ return ret;
+}
+
+static int ad7191_write_raw_get_fmt(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, long mask)
+{
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ return IIO_VAL_INT_PLUS_NANO;
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ return IIO_VAL_INT;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad7191_read_avail(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, const int **vals,
+ int *type, int *length, long mask)
+{
+ struct ad7191_state *st = iio_priv(indio_dev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ *vals = (int *)st->scale_avail;
+ *type = IIO_VAL_INT_PLUS_NANO;
+ *length = st->scale_avail_size * 2;
+ return IIO_AVAIL_LIST;
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ *vals = (int *)st->samp_freq_avail;
+ *type = IIO_VAL_INT;
+ *length = st->samp_freq_avail_size;
+ return IIO_AVAIL_LIST;
+ }
+
+ return -EINVAL;
+}
+
+static const struct iio_info ad7191_info = {
+ .read_raw = ad7191_read_raw,
+ .write_raw = ad7191_write_raw,
+ .write_raw_get_fmt = ad7191_write_raw_get_fmt,
+ .read_avail = ad7191_read_avail,
+ .validate_trigger = ad_sd_validate_trigger,
+};
+
+static const struct iio_chan_spec ad7191_channels[] = {
+ {
+ .type = IIO_TEMP,
+ .address = AD7191_CH_TEMP,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_OFFSET) |
+ BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+ .scan_type = {
+ .sign = 'u',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_BE,
+ },
+ },
+ {
+ .type = IIO_VOLTAGE,
+ .differential = 1,
+ .indexed = 1,
+ .channel = 1,
+ .channel2 = 2,
+ .address = AD7191_CH_AIN1_AIN2,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_OFFSET) |
+ BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+ .info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SCALE),
+ .scan_index = 1,
+ .scan_type = {
+ .sign = 'u',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_BE,
+ },
+ },
+ {
+ .type = IIO_VOLTAGE,
+ .differential = 1,
+ .indexed = 1,
+ .channel = 3,
+ .channel2 = 4,
+ .address = AD7191_CH_AIN3_AIN4,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_OFFSET) |
+ BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+ .info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SCALE),
+ .scan_index = 2,
+ .scan_type = {
+ .sign = 'u',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_BE,
+ },
+ },
+ IIO_CHAN_SOFT_TIMESTAMP(3),
+};
+
+static int ad7191_probe(struct spi_device *spi)
+{
+ struct device *dev = &spi->dev;
+ struct ad7191_state *st;
+ struct iio_dev *indio_dev;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ st = iio_priv(indio_dev);
+
+ ret = devm_mutex_init(dev, &st->lock);
+ if (ret)
+ return ret;
+
+ indio_dev->name = "ad7191";
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = ad7191_channels;
+ indio_dev->num_channels = ARRAY_SIZE(ad7191_channels);
+ indio_dev->info = &ad7191_info;
+
+ ret = ad_sd_init(&st->sd, indio_dev, spi, &ad7191_sigma_delta_info);
+ if (ret)
+ return ret;
+
+ ret = devm_ad_sd_setup_buffer_and_trigger(dev, indio_dev);
+ if (ret)
+ return ret;
+
+ ret = ad7191_setup(indio_dev);
+ if (ret)
+ return ret;
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id ad7191_of_match[] = {
+ { .compatible = "adi,ad7191", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ad7191_of_match);
+
+static const struct spi_device_id ad7191_id_table[] = {
+ { "ad7191" },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, ad7191_id_table);
+
+static struct spi_driver ad7191_driver = {
+ .driver = {
+ .name = "ad7191",
+ .of_match_table = ad7191_of_match,
+ },
+ .probe = ad7191_probe,
+ .id_table = ad7191_id_table,
+};
+module_spi_driver(ad7191_driver);
+
+MODULE_AUTHOR("Alisa-Dariana Roman <alisa.roman@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD7191 ADC");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_AD_SIGMA_DELTA");
--
2.43.0