[PATCH v3 2/2] iio: adc: add ltc2309 support

From: Liam Beguin
Date: Mon Aug 28 2023 - 22:43:41 EST

The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.

This implements support for all single-ended and differential channels,
in unipolar mode only.

Signed-off-by: Liam Beguin <liambeguin@xxxxxxxxx>
---
drivers/iio/adc/Kconfig | 10 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ltc2309.c | 249 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 260 insertions(+)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index dc14bde31ac1..6ec18e02faf9 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -607,6 +607,16 @@ config LPC32XX_ADC
activate only one via device tree selection. Provides direct access
via sysfs.

+config LTC2309
+ tristate "Linear Technology LTC2309 ADC driver"
+ depends on I2C
+ help
+ Say yes here to build support for Linear Technology LTC2309, a low
+ noise, low power, 8-channel, 12-bit SAR ADC
+
+ This driver can also be built as a module. If so, the module will
+ be called ltc2309.
+
config LTC2471
tristate "Linear Technology LTC2471 and LTC2473 ADC driver"
depends on I2C
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index eb6e891790fb..fbd86184ec94 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -56,6 +56,7 @@ obj-$(CONFIG_INTEL_MRFLD_ADC) += intel_mrfld_adc.o
obj-$(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_LTC2471) += ltc2471.o
obj-$(CONFIG_LTC2485) += ltc2485.o
obj-$(CONFIG_LTC2496) += ltc2496.o ltc2497-core.o
diff --git a/drivers/iio/adc/ltc2309.c b/drivers/iio/adc/ltc2309.c
new file mode 100644
index 000000000000..3f8e1d238639
--- /dev/null
+++ b/drivers/iio/adc/ltc2309.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The LTC2309 is an 8-Channel, 12-Bit SAR ADC with an I2C Interface.
+ *
+ * Datasheet:
+ * https://www.analog.com/media/en/technical-documentation/data-sheets/2309fd.pdf
+ *
+ * Copyright (c) 2023, Liam Beguin <liambeguin@xxxxxxxxx>
+ */
+#include <linux/bitfield.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regulator/consumer.h>
+
+#define LTC2309_ADC_RESOLUTION 12
+
+#define LTC2309_DIN_CH_MASK GENMASK(7, 4)
+#define LTC2309_DIN_SDN BIT(7)
+#define LTC2309_DIN_OSN BIT(6)
+#define LTC2309_DIN_S1 BIT(5)
+#define LTC2309_DIN_S0 BIT(4)
+#define LTC2309_DIN_UNI BIT(3)
+#define LTC2309_DIN_SLEEP BIT(2)
+
+/**
+ * struct ltc2309 - internal device data structure
+ * @dev: Device reference
+ * @client: I2C reference
+ * @vref: External reference source
+ * @lock: Lock to serialize data access
+ * @vref_mv Internal voltage reference
+ */
+struct ltc2309 {
+ struct device *dev;
+ struct i2c_client *client;
+ struct regulator *vref;
+ struct mutex lock; /* serialize data access */
+ int vref_mv;
+};
+
+/* Order matches expected channel address, See datasheet Table 1. */
+enum ltc2309_channels {
+ LTC2309_CH0_CH1 = 0,
+ LTC2309_CH2_CH3,
+ LTC2309_CH4_CH5,
+ LTC2309_CH6_CH7,
+ LTC2309_CH1_CH0,
+ LTC2309_CH3_CH2,
+ LTC2309_CH5_CH4,
+ LTC2309_CH7_CH6,
+ LTC2309_CH0,
+ LTC2309_CH2,
+ LTC2309_CH4,
+ LTC2309_CH6,
+ LTC2309_CH1,
+ LTC2309_CH3,
+ LTC2309_CH5,
+ LTC2309_CH7,
+};
+
+#define LTC2309_CHAN(_chan, _addr) { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .address = _addr, \
+ .channel = _chan, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+#define LTC2309_DIFF_CHAN(_chan, _chan2, _addr) { \
+ .type = IIO_VOLTAGE, \
+ .differential = 1, \
+ .indexed = 1, \
+ .address = _addr, \
+ .channel = _chan, \
+ .channel2 = _chan2, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec ltc2309_channels[] = {
+ LTC2309_CHAN(0, LTC2309_CH0),
+ LTC2309_CHAN(1, LTC2309_CH1),
+ LTC2309_CHAN(2, LTC2309_CH2),
+ LTC2309_CHAN(3, LTC2309_CH3),
+ LTC2309_CHAN(4, LTC2309_CH4),
+ LTC2309_CHAN(5, LTC2309_CH5),
+ LTC2309_CHAN(6, LTC2309_CH6),
+ LTC2309_CHAN(7, LTC2309_CH7),
+ LTC2309_DIFF_CHAN(0, 1, LTC2309_CH0_CH1),
+ LTC2309_DIFF_CHAN(2, 3, LTC2309_CH2_CH3),
+ LTC2309_DIFF_CHAN(4, 5, LTC2309_CH4_CH5),
+ LTC2309_DIFF_CHAN(6, 7, LTC2309_CH6_CH7),
+ LTC2309_DIFF_CHAN(1, 0, LTC2309_CH1_CH0),
+ LTC2309_DIFF_CHAN(3, 2, LTC2309_CH3_CH2),
+ LTC2309_DIFF_CHAN(5, 4, LTC2309_CH5_CH4),
+ LTC2309_DIFF_CHAN(7, 6, LTC2309_CH7_CH6),
+};
+
+static int ltc2309_read_raw_channel(struct ltc2309 *ltc2309,
+ unsigned long address, int *val)
+{
+ int ret;
+ u16 buf;
+ u8 din;
+
+ din = FIELD_PREP(LTC2309_DIN_CH_MASK, address & 0x0f) |
+ FIELD_PREP(LTC2309_DIN_UNI, 1) |
+ FIELD_PREP(LTC2309_DIN_SLEEP, 0);
+
+ ret = i2c_smbus_write_byte(ltc2309->client, din);
+ if (ret < 0) {
+ dev_err(ltc2309->dev, "i2c command failed: %pe\n",
+ ERR_PTR(ret));
+ return ret;
+ }
+
+ ret = i2c_master_recv(ltc2309->client, (char *)&buf, 2);
+ if (ret < 0) {
+ dev_err(ltc2309->dev, "i2c read failed: %pe\n", ERR_PTR(ret));
+ return ret;
+ }
+
+ *val = be16_to_cpu(buf) >> 4;
+
+ return ret;
+}
+
+static int ltc2309_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long mask)
+{
+ struct ltc2309 *ltc2309 = iio_priv(indio_dev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&ltc2309->lock);
+ ret = ltc2309_read_raw_channel(ltc2309, chan->address, val);
+ mutex_unlock(&ltc2309->lock);
+ if (ret < 0)
+ return -EINVAL;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = ltc2309->vref_mv;
+ *val2 = LTC2309_ADC_RESOLUTION;
+ return IIO_VAL_FRACTIONAL_LOG2;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info ltc2309_info = {
+ .read_raw = ltc2309_read_raw,
+};
+
+void ltc2309_regulator_disable(void *regulator)
+{
+ struct regulator *r = (struct regulator *)regulator;
+
+ regulator_disable(r);
+}
+
+static int ltc2309_probe(struct i2c_client *client)
+{
+ struct iio_dev *indio_dev;
+ struct ltc2309 *ltc2309;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*ltc2309));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ ltc2309 = iio_priv(indio_dev);
+ ltc2309->dev = &indio_dev->dev;
+ ltc2309->client = client;
+ ltc2309->vref_mv = 4096; /* Default to the internal ref */
+
+ indio_dev->name = "ltc2309";
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = ltc2309_channels;
+ indio_dev->num_channels = ARRAY_SIZE(ltc2309_channels);
+ indio_dev->info = &ltc2309_info;
+
+ ltc2309->vref = devm_regulator_get_optional(&client->dev, "vref");
+ if (IS_ERR(ltc2309->vref)) {
+ ret = PTR_ERR(ltc2309->vref);
+ if (ret == -ENODEV)
+ ltc2309->vref = NULL;
+ else
+ return ret;
+ }
+
+ if (ltc2309->vref) {
+ ret = regulator_enable(ltc2309->vref);
+ if (ret)
+ return dev_err_probe(ltc2309->dev, ret,
+ "failed to enable vref\n");
+
+ ret = devm_add_action_or_reset(ltc2309->dev,
+ ltc2309_regulator_disable,
+ ltc2309->vref);
+ if (ret) {
+ return dev_err_probe(ltc2309->dev, ret,
+ "failed to add regulator_disable action: %d\n",
+ ret);
+ return ret;
+ }
+
+ ret = regulator_get_voltage(ltc2309->vref);
+ if (ret < 0)
+ return ret;
+
+ ltc2309->vref_mv = ret / 1000;
+ }
+
+ mutex_init(&ltc2309->lock);
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct of_device_id ltc2309_of_match[] = {
+ { .compatible = "lltc,ltc2309" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ltc2309_of_match);
+
+static const struct i2c_device_id ltc2309_id[] = {
+ { "ltc2309" },
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, ltc2309_id);
+
+static struct i2c_driver ltc2309_driver = {
+ .driver = {
+ .name = "ltc2309",
+ .of_match_table = ltc2309_of_match,
+ },
+ .probe = ltc2309_probe,
+ .id_table = ltc2309_id,
+};
+module_i2c_driver(ltc2309_driver);
+
+MODULE_AUTHOR("Liam Beguin <liambeguin@xxxxxxxxx>");
+MODULE_DESCRIPTION("Linear Technology LTC2309 ADC");
+MODULE_LICENSE("GPL v2");

--
2.39.0