[PATCH v6 3/3] iio: dac: ad3530r: Add driver for AD3530R and AD3531R

Kim Seer Paller
2025-04-25T12:55:47Z

The AD3530/AD3530R (8-channel) and AD3531/AD3531R (4-channel) are
low-power, 16-bit, buffered voltage output DACs with software-
programmable gain controls, providing full-scale output spans of 2.5V or
5V for reference voltages of 2.5V. These devices operate from a single
2.7V to 5.5V supply and are guaranteed monotonic by design. The "R"
variants include a 2.5V, 5ppm/°C internal reference, which is disabled
by default.

Support for monitoring internal die temperature, output voltages, and
current of a selected channel via the MUXOUT pin using an external ADC
is currently not implemented.

Signed-off-by: Kim Seer Paller <kimseer.paller@analog.com>
---
MAINTAINERS | 1 +
drivers/iio/dac/Kconfig | 11 +
drivers/iio/dac/Makefile | 1 +
drivers/iio/dac/ad3530r.c | 515 ++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 528 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 4ca59fc1bf25aa49fecf78a90b2e1b73f25a2c05..25356d5a1a09e5ff6e7ed8eaa98a8ea990e79d8e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1306,6 +1306,7 @@ L: linux-iio@vger.kernel.org
S: Supported
W: https://ez.analog.com/linux-software-drivers
F: Documentation/devicetree/bindings/iio/dac/adi,ad3530r.yaml
+F: drivers/iio/dac/ad3530r.c

ANALOG DEVICES INC AD3552R DRIVER
M: Nuno Sá <nuno.sa@analog.com>
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 4811ea973125a0dea1f8a9cdee1e0c045bc21981..e0996dc014a3d538ab6b4e0d50ff54ede50f1527 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -6,6 +6,17 @@

menu "Digital to analog converters"

+config AD3530R
+ tristate "Analog Devices AD3530R and Similar DACs driver"
+ depends on SPI
+ select REGMAP_SPI
+ help
+ Say yes here to build support for Analog Devices AD3530R, AD3531R
+ Digital to Analog Converter.
+
+ To compile this driver as a module, choose M here: the
+ module will be called ad3530r.
+
config AD3552R_HS
tristate "Analog Devices AD3552R DAC High Speed driver"
select AD3552R_LIB
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 8dd6cce81ed1152be4cf0af9ef877b5482ceb347..3684cd52b7fa9bc0ad9f855323dcbb2e4965c404 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -4,6 +4,7 @@
#

# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_AD3530R) += ad3530r.o
obj-$(CONFIG_AD3552R_HS) += ad3552r-hs.o
obj-$(CONFIG_AD3552R_LIB) += ad3552r-common.o
obj-$(CONFIG_AD3552R) += ad3552r.o
diff --git a/drivers/iio/dac/ad3530r.c b/drivers/iio/dac/ad3530r.c
new file mode 100644
index 0000000000000000000000000000000000000000..2b3057e02e260a13add3237d8b93377fbd9aa81f
--- /dev/null
+++ b/drivers/iio/dac/ad3530r.c
@@ -0,0 +1,515 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AD3530R/AD3530 8-channel, 16-bit Voltage Output DAC Driver
+ * AD3531R/AD3531 4-channel, 16-bit Voltage Output DAC Driver
+ *
+ * Copyright 2025 Analog Devices Inc.
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/cleanup.h>
+#include <linux/delay.h>
+#include <linux/dev_printk.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/kstrtox.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#define AD3530R_INTERFACE_CONFIG_A 0x00
+#define AD3530R_OUTPUT_OPERATING_MODE_0 0x20
+#define AD3530R_OUTPUT_OPERATING_MODE_1 0x21
+#define AD3530R_OUTPUT_CONTROL_0 0x2A
+#define AD3530R_REFERENCE_CONTROL_0 0x3C
+#define AD3530R_SW_LDAC_TRIG_A 0xE5
+#define AD3530R_INPUT_CH 0xEB
+#define AD3530R_MAX_REG_ADDR 0xF9
+
+#define AD3531R_SW_LDAC_TRIG_A 0xDD
+#define AD3531R_INPUT_CH 0xE3
+
+#define AD3530R_SLD_TRIG_A BIT(7)
+#define AD3530R_OUTPUT_CONTROL_RANGE BIT(2)
+#define AD3530R_REFERENCE_CONTROL_SEL BIT(0)
+#define AD3530R_REG_VAL_MASK GENMASK(15, 0)
+#define AD3530R_OP_MODE_CHAN_MSK(chan) (GENMASK(1, 0) << 2 * chan)
+
+#define AD3530R_SW_RESET (BIT(7) | BIT(0))
+#define AD3530R_INTERNAL_VREF_mV 2500
+#define AD3530R_LDAC_PULSE_US 100
+
+#define AD3530R_DAC_MAX_VAL GENMASK(15, 0)
+#define AD3530R_MAX_CHANNELS 8
+#define AD3531R_MAX_CHANNELS 4
+
+enum ad3530r_mode {
+ AD3530R_NORMAL_OP,
+ AD3530R_POWERDOWN_1K,
+ AD3530R_POWERDOWN_7K7,
+ AD3530R_POWERDOWN_32K,
+};
+
+struct ad3530r_chan {
+ enum ad3530r_mode powerdown_mode;
+ bool powerdown;
+};
+
+struct ad3530r_chip_info {
+ const char *name;
+ const struct iio_chan_spec *channels;
+ int (*input_ch_reg)(unsigned int channel);
+ unsigned int num_channels;
+ unsigned int sw_ldac_trig_reg;
+ bool internal_ref_support;
+};
+
+struct ad3530r_state {
+ struct regmap *regmap;
+ /* lock to protect against multiple access to the device and shared data */
+ struct mutex lock;
+ struct ad3530r_chan chan[AD3530R_MAX_CHANNELS];
+ const struct ad3530r_chip_info *chip_info;
+ struct gpio_desc *ldac_gpio;
+ int vref_mV;
+ /*
+ * DMA (thus cache coherency maintenance) may require the transfer
+ * buffers to live in their own cache lines.
+ */
+ __be16 buf __aligned(IIO_DMA_MINALIGN);
+};
+
+static int ad3530r_input_ch_reg(unsigned int channel)
+{
+ return 2 * channel + AD3530R_INPUT_CH;
+}
+
+static int ad3531r_input_ch_reg(unsigned int channel)
+{
+ return 2 * channel + AD3531R_INPUT_CH;
+}
+
+static const char * const ad3530r_powerdown_modes[] = {
+ "1kohm_to_gnd",
+ "7.7kohm_to_gnd",
+ "32kohm_to_gnd",
+};
+
+static int ad3530r_get_powerdown_mode(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+
+ guard(mutex)(&st->lock);
+ return st->chan[chan->channel].powerdown_mode - 1;
+}
+
+static int ad3530r_set_powerdown_mode(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ unsigned int mode)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+
+ guard(mutex)(&st->lock);
+ st->chan[chan->channel].powerdown_mode = mode + 1;
+
+ return 0;
+}
+
+static const struct iio_enum ad3530r_powerdown_mode_enum = {
+ .items = ad3530r_powerdown_modes,
+ .num_items = ARRAY_SIZE(ad3530r_powerdown_modes),
+ .get = ad3530r_get_powerdown_mode,
+ .set = ad3530r_set_powerdown_mode,
+};
+
+static ssize_t ad3530r_get_dac_powerdown(struct iio_dev *indio_dev,
+ uintptr_t private,
+ const struct iio_chan_spec *chan,
+ char *buf)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+
+ guard(mutex)(&st->lock);
+ return sysfs_emit(buf, "%d\n", st->chan[chan->channel].powerdown);
+}
+
+static ssize_t ad3530r_set_dac_powerdown(struct iio_dev *indio_dev,
+ uintptr_t private,
+ const struct iio_chan_spec *chan,
+ const char *buf, size_t len)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+ int ret;
+ unsigned int mask, val, reg, pdmode;
+ bool powerdown;
+
+ ret = kstrtobool(buf, &powerdown);
+ if (ret)
+ return ret;
+
+ guard(mutex)(&st->lock);
+ mask = AD3530R_OP_MODE_CHAN_MSK(chan->channel);
+ reg = chan->channel < AD3531R_MAX_CHANNELS ?
+ AD3530R_OUTPUT_OPERATING_MODE_0 :
+ AD3530R_OUTPUT_OPERATING_MODE_1;
+ pdmode = powerdown ? st->chan[chan->channel].powerdown_mode : 0;
+ val = pdmode << 2 * chan->channel;
+
+ ret = regmap_update_bits(st->regmap, reg, mask, val);
+ if (ret)
+ return ret;
+
+ st->chan[chan->channel].powerdown = powerdown;
+
+ return len;
+}
+
+static int ad3530r_trigger_hw_ldac(struct gpio_desc *ldac_gpio)
+{
+ gpiod_set_value_cansleep(ldac_gpio, 1);
+ fsleep(AD3530R_LDAC_PULSE_US);
+ gpiod_set_value_cansleep(ldac_gpio, 0);
+
+ return 0;
+}
+
+static int ad3530r_dac_write(struct ad3530r_state *st, unsigned int chan,
+ unsigned int val)
+{
+ int ret;
+
+ guard(mutex)(&st->lock);
+ st->buf = cpu_to_be16(val);
+
+ ret = regmap_bulk_write(st->regmap, st->chip_info->input_ch_reg(chan),
+ &st->buf, sizeof(st->buf));
+ if (ret)
+ return ret;
+
+ if (st->ldac_gpio)
+ return ad3530r_trigger_hw_ldac(st->ldac_gpio);
+
+ return regmap_set_bits(st->regmap, st->chip_info->sw_ldac_trig_reg,
+ AD3530R_SLD_TRIG_A);
+}
+
+static int ad3530r_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long info)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+ int ret;
+
+ guard(mutex)(&st->lock);
+ switch (info) {
+ case IIO_CHAN_INFO_RAW:
+ ret = regmap_bulk_read(st->regmap,
+ st->chip_info->input_ch_reg(chan->channel),
+ &st->buf, sizeof(st->buf));
+ if (ret)
+ return ret;
+
+ *val = FIELD_GET(AD3530R_REG_VAL_MASK, be16_to_cpu(st->buf));
+
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = st->vref_mV;
+ *val2 = 16;
+
+ return IIO_VAL_FRACTIONAL_LOG2;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad3530r_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long info)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+
+ switch (info) {
+ case IIO_CHAN_INFO_RAW:
+ if (val < 0 || val > AD3530R_DAC_MAX_VAL)
+ return -EINVAL;
+
+ return ad3530r_dac_write(st, chan->channel, val);
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ad3530r_reg_access(struct iio_dev *indio_dev, unsigned int reg,
+ unsigned int writeval, unsigned int *readval)
+{
+ struct ad3530r_state *st = iio_priv(indio_dev);
+
+ if (readval)
+ return regmap_read(st->regmap, reg, readval);
+
+ return regmap_write(st->regmap, reg, writeval);
+}
+
+static const struct iio_chan_spec_ext_info ad3530r_ext_info[] = {
+ {
+ .name = "powerdown",
+ .shared = IIO_SEPARATE,
+ .read = ad3530r_get_dac_powerdown,
+ .write = ad3530r_set_dac_powerdown,
+ },
+ IIO_ENUM("powerdown_mode", IIO_SEPARATE, &ad3530r_powerdown_mode_enum),
+ IIO_ENUM_AVAILABLE("powerdown_mode", IIO_SHARED_BY_TYPE,
+ &ad3530r_powerdown_mode_enum),
+ { }
+};
+
+#define AD3530R_CHAN(_chan) \
+{ \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = _chan, \
+ .output = 1, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ BIT(IIO_CHAN_INFO_SCALE), \
+ .ext_info = ad3530r_ext_info, \
+}
+
+static const struct iio_chan_spec ad3530r_channels[] = {
+ AD3530R_CHAN(0),
+ AD3530R_CHAN(1),
+ AD3530R_CHAN(2),
+ AD3530R_CHAN(3),
+ AD3530R_CHAN(4),
+ AD3530R_CHAN(5),
+ AD3530R_CHAN(6),
+ AD3530R_CHAN(7),
+};
+
+static const struct iio_chan_spec ad3531r_channels[] = {
+ AD3530R_CHAN(0),
+ AD3530R_CHAN(1),
+ AD3530R_CHAN(2),
+ AD3530R_CHAN(3),
+};
+
+static const struct ad3530r_chip_info ad3530_chip = {
+ .name = "ad3530",
+ .channels = ad3530r_channels,
+ .num_channels = ARRAY_SIZE(ad3530r_channels),
+ .sw_ldac_trig_reg = AD3530R_SW_LDAC_TRIG_A,
+ .input_ch_reg = ad3530r_input_ch_reg,
+ .internal_ref_support = false,
+};
+
+static const struct ad3530r_chip_info ad3530r_chip = {
+ .name = "ad3530r",
+ .channels = ad3530r_channels,
+ .num_channels = ARRAY_SIZE(ad3530r_channels),
+ .sw_ldac_trig_reg = AD3530R_SW_LDAC_TRIG_A,
+ .input_ch_reg = ad3530r_input_ch_reg,
+ .internal_ref_support = true,
+};
+
+static const struct ad3530r_chip_info ad3531_chip = {
+ .name = "ad3531",
+ .channels = ad3531r_channels,
+ .num_channels = ARRAY_SIZE(ad3531r_channels),
+ .sw_ldac_trig_reg = AD3531R_SW_LDAC_TRIG_A,
+ .input_ch_reg = ad3531r_input_ch_reg,
+ .internal_ref_support = false,
+};
+
+static const struct ad3530r_chip_info ad3531r_chip = {
+ .name = "ad3531r",
+ .channels = ad3531r_channels,
+ .num_channels = ARRAY_SIZE(ad3531r_channels),
+ .sw_ldac_trig_reg = AD3531R_SW_LDAC_TRIG_A,
+ .input_ch_reg = ad3531r_input_ch_reg,
+ .internal_ref_support = true,
+};
+
+static int ad3530r_setup(struct ad3530r_state *st, int vref)
+{
+ struct device *dev = regmap_get_device(st->regmap);
+ struct gpio_desc *reset_gpio;
+ int i, ret;
+ u8 range_multiplier, val;
+
+ reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+ if (IS_ERR(reset_gpio))
+ return dev_err_probe(dev, PTR_ERR(reset_gpio),
+ "Failed to get reset GPIO\n");
+
+ if (reset_gpio) {
+ /* Perform hardware reset */
+ fsleep(1 * USEC_PER_MSEC);
+ gpiod_set_value_cansleep(reset_gpio, 0);
+ } else {
+ /* Perform software reset */
+ ret = regmap_update_bits(st->regmap, AD3530R_INTERFACE_CONFIG_A,
+ AD3530R_SW_RESET, AD3530R_SW_RESET);
+ if (ret)
+ return ret;
+ }
+
+ fsleep(10 * USEC_PER_MSEC);
+
+ range_multiplier = 1;
+ if (device_property_read_bool(dev, "adi,range-double")) {
+ ret = regmap_set_bits(st->regmap, AD3530R_OUTPUT_CONTROL_0,
+ AD3530R_OUTPUT_CONTROL_RANGE);
+ if (ret)
+ return ret;
+
+ range_multiplier = 2;
+ }
+
+ if (st->chip_info->internal_ref_support && vref == 0) {
+ ret = regmap_set_bits(st->regmap, AD3530R_REFERENCE_CONTROL_0,
+ AD3530R_REFERENCE_CONTROL_SEL);
+ if (ret)
+ return ret;
+
+ st->vref_mV = range_multiplier * AD3530R_INTERNAL_VREF_mV;
+ }
+
+ if (vref > 0)
+ st->vref_mV = range_multiplier * vref / MILLI;
+
+ /* Set normal operating mode for all channels */
+ val = FIELD_PREP(AD3530R_OP_MODE_CHAN_MSK(0), AD3530R_NORMAL_OP) |
+ FIELD_PREP(AD3530R_OP_MODE_CHAN_MSK(1), AD3530R_NORMAL_OP) |
+ FIELD_PREP(AD3530R_OP_MODE_CHAN_MSK(2), AD3530R_NORMAL_OP) |
+ FIELD_PREP(AD3530R_OP_MODE_CHAN_MSK(3), AD3530R_NORMAL_OP);
+
+ ret = regmap_write(st->regmap, AD3530R_OUTPUT_OPERATING_MODE_0, val);
+ if (ret)
+ return ret;
+
+ if (st->chip_info->num_channels > 4) {
+ ret = regmap_write(st->regmap, AD3530R_OUTPUT_OPERATING_MODE_1,
+ val);
+ if (ret)
+ return ret;
+ }
+
+ for (i = 0; i < st->chip_info->num_channels; i++)
+ st->chan[i].powerdown_mode = AD3530R_POWERDOWN_32K;
+
+ st->ldac_gpio = devm_gpiod_get_optional(dev, "ldac", GPIOD_OUT_LOW);
+ if (IS_ERR(st->ldac_gpio))
+ return dev_err_probe(dev, PTR_ERR(st->ldac_gpio),
+ "Failed to get ldac GPIO\n");
+
+ return 0;
+}
+
+static const struct regmap_config ad3530r_regmap_config = {
+ .reg_bits = 16,
+ .val_bits = 8,
+ .max_register = AD3530R_MAX_REG_ADDR,
+};
+
+static const struct iio_info ad3530r_info = {
+ .read_raw = ad3530r_read_raw,
+ .write_raw = ad3530r_write_raw,
+ .debugfs_reg_access = ad3530r_reg_access,
+};
+
+static int ad3530r_probe(struct spi_device *spi)
+{
+ static const char * const regulators[] = { "vdd", "iovdd" };
+ struct device *dev = &spi->dev;
+ struct iio_dev *indio_dev;
+ struct ad3530r_state *st;
+ int ret, vref;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ st = iio_priv(indio_dev);
+
+ st->regmap = devm_regmap_init_spi(spi, &ad3530r_regmap_config);
+ if (IS_ERR(st->regmap))
+ return dev_err_probe(dev, PTR_ERR(st->regmap),
+ "Failed to init regmap");
+
+ ret = devm_mutex_init(dev, &st->lock);
+ if (ret)
+ return ret;
+
+ st->chip_info = spi_get_device_match_data(spi);
+ if (!st->chip_info)
+ return -ENODEV;
+
+ ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(regulators),
+ regulators);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to enable regulators\n");
+
+ vref = devm_regulator_get_enable_read_voltage(dev, "ref");
+ if (vref < 0 && vref != -ENODEV)
+ return vref;
+
+ if (vref == -ENODEV)
+ vref = 0;
+
+ if (!st->chip_info->internal_ref_support && vref == 0)
+ return -ENODEV;
+
+ ret = ad3530r_setup(st, vref);
+ if (ret)
+ return ret;
+
+ indio_dev->name = st->chip_info->name;
+ indio_dev->info = &ad3530r_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = st->chip_info->channels;
+ indio_dev->num_channels = st->chip_info->num_channels;
+
+ return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct spi_device_id ad3530r_id[] = {
+ { "ad3530", (kernel_ulong_t)&ad3530_chip },
+ { "ad3530r", (kernel_ulong_t)&ad3530r_chip },
+ { "ad3531", (kernel_ulong_t)&ad3531_chip },
+ { "ad3531r", (kernel_ulong_t)&ad3531r_chip },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, ad3530r_id);
+
+static const struct of_device_id ad3530r_of_match[] = {
+ { .compatible = "adi,ad3530", .data = &ad3530_chip },
+ { .compatible = "adi,ad3530r", .data = &ad3530r_chip },
+ { .compatible = "adi,ad3531", .data = &ad3531_chip },
+ { .compatible = "adi,ad3531r", .data = &ad3531r_chip },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ad3530r_of_match);
+
+static struct spi_driver ad3530r_driver = {
+ .driver = {
+ .name = "ad3530r",
+ .of_match_table = ad3530r_of_match,
+ },
+ .probe = ad3530r_probe,
+ .id_table = ad3530r_id,
+};
+module_spi_driver(ad3530r_driver);
+
+MODULE_AUTHOR("Kim Seer Paller <kimseer.paller@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD3530R and Similar DACs Driver");
+MODULE_LICENSE("GPL");

--
2.34.1