--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * IIO driver for Lite-On LTR390 ALS and UV sensor
+ * (7-bit I2C slave address 0x53)
+ *
+ * Based on the work of:
+ * Shreeya Patel and Shi Zhigang (LTRF216 Driver)
+ *
+ * Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
+ *
+ * Datasheet:
+ * https://optoelectronics.liteon.com/upload/download/DS86-2015-0004/LTR-390UV_Final_%20DS_V1%201.pdf
+ *
+ * TODO:
+ * - Support for configurable gain and resolution
+ * - Sensor suspend/resume support
+ * - Add support for reading the ALS
+ * - Interrupt support
+ */
+
+#include <linux/i2c.h>
+#include <linux/math.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+
+#include <linux/iio/iio.h>
+
+#include <asm/unaligned.h>
+
+#define LTR390_MAIN_CTRL 0x00
+#define LTR390_PART_ID 0x06
+#define LTR390_UVS_DATA 0x10
+
+#define LTR390_SW_RESET BIT(4)
+#define LTR390_UVS_MODE BIT(3)
+#define LTR390_SENSOR_ENABLE BIT(1)
+
+#define LTR390_PART_NUMBER_ID 0xb
+
+/*
+ * At 20-bit resolution (integration time: 400ms) and 18x gain, 2300 counts of
+ * the sensor are equal to 1 UV Index [Datasheet Page#8].
+ *
+ * For the default resolution of 18-bit (integration time: 100ms) and default
+ * gain of 3x, the counts/uvi are calculated as follows:
+ * 2300 / ((3/18) * (100/400)) = 95.83
+ */
+#define LTR390_COUNTS_PER_UVI 96
+
+/*
+ * Window Factor is needed when the device is under Window glass with coated
+ * tinted ink. This is to compensate for the light loss due to the lower
+ * transmission rate of the window glass and helps * in calculating lux.
+ */
+#define LTR390_WINDOW_FACTOR 1
+
+struct ltr390_data {
+ struct regmap *regmap;
+ struct i2c_client *client;
+ /* Protects device from simulataneous reads */
+ struct mutex lock;
+};
+
+static const struct regmap_config ltr390_regmap_config = {
+ .name = "ltr390",
+ .reg_bits = 8,
+ .reg_stride = 1,
+ .val_bits = 8,
+};
+
+static int ltr390_register_read(struct ltr390_data *data, u8 register_address)
+{
+ struct device *dev = &data->client->dev;
+ int ret;
+ u8 recieve_buffer[3];
+
+ guard(mutex)(&data->lock);
+
+ ret = regmap_bulk_read(data->regmap, register_address, recieve_buffer,
+ sizeof(recieve_buffer));
+ if (ret) {
+ dev_err(dev, "failed to read measurement data");
+ return ret;
+ }
+
+ return get_unaligned_le24(recieve_buffer);
+}
+
+static int ltr390_read_raw(struct iio_dev *iio_device,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long mask)
+{
+ int ret;
+ struct ltr390_data *data = iio_priv(iio_device);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ ret = ltr390_register_read(data, LTR390_UVS_DATA);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = LTR390_WINDOW_FACTOR;
+ *val2 = LTR390_COUNTS_PER_UVI;
+ return IIO_VAL_FRACTIONAL;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info ltr390_info = {
+ .read_raw = ltr390_read_raw,
+};
+
+static const struct iio_chan_spec ltr390_channel = {
+ .type = IIO_UVINDEX,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE)
+};
+
+static int ltr390_probe(struct i2c_client *client)
+{
+ struct ltr390_data *data;
+ struct iio_dev *indio_dev;
+ struct device *dev;
+ int ret, part_number;
+
+ dev = &client->dev;
+ indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+
+ data->regmap = devm_regmap_init_i2c(client, <r390_regmap_config);
+ if (IS_ERR(data->regmap))
+ return dev_err_probe(dev, PTR_ERR(data->regmap),
+ "regmap initialization failed\n");
+
+ data->client = client;
+ mutex_init(&data->lock);
+
+ indio_dev->info = <r390_info;
+ indio_dev->channels = <r390_channel;
+ indio_dev->num_channels = 1;
+ indio_dev->name = "ltr390";
+
+ ret = regmap_read(data->regmap, LTR390_PART_ID, &part_number);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to get sensor's part id\n");
+ /* Lower 4 bits of `part_number` change with hardware revisions */
+ if (part_number >> 4 != LTR390_PART_NUMBER_ID)
+ dev_info(dev, "received invalid product id: 0x%x", part_number);
+ dev_dbg(dev, "LTR390, product id: 0x%x\n", part_number);
+
+ /* reset sensor, chip fails to respond to this, so ignore any errors */
+ regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_SW_RESET);
+
+ /* Wait for the registers to reset before proceeding */
+ usleep_range(1000, 2000);
+
+ ret = regmap_set_bits(data->regmap, LTR390_MAIN_CTRL,
+ LTR390_SENSOR_ENABLE | LTR390_UVS_MODE);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to enable the sensor\n");
+
+ return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct i2c_device_id ltr390_id[] = {
+ { "ltr390" },
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, ltr390_id);
+
+static const struct of_device_id ltr390_of_table[] = {
+ { .compatible = "liteon,ltr390" },
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ltr390_of_table);
+
+static struct i2c_driver ltr390_driver = {
+ .driver = {
+ .name = "ltr390",
+ .of_match_table = ltr390_of_table,
+ },
+ .probe = ltr390_probe,
+ .id_table = ltr390_id,
+};
+module_i2c_driver(ltr390_driver);
+
+MODULE_AUTHOR("Anshul Dalal <anshulusr@gmail.com>");
+MODULE_DESCRIPTION("Lite-On LTR390 ALS and UV sensor Driver");
+MODULE_LICENSE("GPL");
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