[PATCH 2/2] iio: light: driver for Lite-On ltr390

Anshul Dalal
2023-11-09T09:07:26Z

Implements driver for the Ambient/UV Light sensor LTR390.
The driver exposes two ways of getting sensor readings:
1. Raw UV Counts directly from the sensor
2. The computed UV Index value with a percision of 2 decimal places

NOTE: Ambient light sensing has not been implemented yet.

Datasheet:
https://optoelectronics.liteon.com/upload/download/DS86-2015-0004/LTR-390UV_Final_%20DS_V1%201.pdf

Driver tested on RPi Zero 2W

Signed-off-by: Anshul Dalal <anshulusr@gmail.com>
---
MAINTAINERS | 7 ++
drivers/iio/light/Kconfig | 11 ++
drivers/iio/light/Makefile | 1 +
drivers/iio/light/ltr390.c | 224 +++++++++++++++++++++++++++++++++++++
4 files changed, 243 insertions(+)
create mode 100644 drivers/iio/light/ltr390.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 81d5fc0bba68..c9f2238673f0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12484,6 +12484,13 @@ S: Maintained
W: http://linux-test-project.github.io/
T: git https://github.com/linux-test-project/ltp.git

+LTR390 AMBIENT/UV LIGHT SENSOR DRIVER
+M: Anshul Dalal <anshulusr@gmail.com>
+L: linux-iio@vger.kernel.org
+S: Maintained
+F: Documentation/devicetree/bindings/iio/light/liteon,ltr390.yaml
+F: drivers/iio/light/ltr390.c
+
LYNX 28G SERDES PHY DRIVER
M: Ioana Ciornei <ioana.ciornei@nxp.com>
L: netdev@vger.kernel.org
diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 45edba797e4c..61993ae79afe 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -347,6 +347,17 @@ config SENSORS_LM3533
changes. The ALS-control output values can be set per zone for the
three current output channels.

+config LTR390
+ tristate "LTR-390UV-01 ambient light and UV sensor"
+ depends on I2C
+ select REGMAP_I2C
+ help
+ If you say yes here you get support for the Lite-On LTR-390UV-01
+ ambient light and UV sensor.
+
+ This driver can also be built as a module. If so, the module
+ will be called ltr390.
+
config LTR501
tristate "LTR-501ALS-01 light sensor"
depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index c0db4c4c36ec..550f8b408bc2 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -30,6 +30,7 @@ obj-$(CONFIG_SENSORS_ISL29028) += isl29028.o
obj-$(CONFIG_ISL29125) += isl29125.o
obj-$(CONFIG_JSA1212) += jsa1212.o
obj-$(CONFIG_SENSORS_LM3533) += lm3533-als.o
+obj-$(CONFIG_LTR390) += ltr390.o
obj-$(CONFIG_LTR501) += ltr501.o
obj-$(CONFIG_LTRF216A) += ltrf216a.o
obj-$(CONFIG_LV0104CS) += lv0104cs.o
diff --git a/drivers/iio/light/ltr390.c b/drivers/iio/light/ltr390.c
new file mode 100644
index 000000000000..1445f944bfd0
--- /dev/null
+++ b/drivers/iio/light/ltr390.c
@@ -0,0 +1,224 @@
+// 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 <asm/unaligned.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/math.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+
+#define LTR390_DEVICE_NAME "ltr390"
+
+#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
+#define LTR390_FRCTIONAL_PERCISION 100
+
+/*
+ * 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;
+ struct mutex lock;
+};
+
+static const struct regmap_config ltr390_regmap_config = {
+ .name = LTR390_DEVICE_NAME,
+ .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];
+
+ mutex_lock(&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: %d\n", ret);
+ mutex_unlock(&data->lock);
+ return ret;
+ }
+
+ mutex_unlock(&data->lock);
+ return get_unaligned_le24(recieve_buffer);
+}
+
+static int ltr390_get_uv_index(struct ltr390_data *data)
+{
+ int ret;
+ int uv_index;
+
+ ret = ltr390_register_read(data, LTR390_UVS_DATA);
+ if (ret < 0)
+ return ret;
+
+ uv_index = DIV_ROUND_CLOSEST(ret * LTR390_FRCTIONAL_PERCISION *
+ LTR390_WINDOW_FACTOR,
+ LTR390_COUNTS_PER_UVI);
+
+ return uv_index;
+}
+
+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_PROCESSED:
+ ret = ltr390_get_uv_index(data);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ *val2 = LTR390_FRCTIONAL_PERCISION;
+ return IIO_VAL_FRACTIONAL;
+ case IIO_CHAN_INFO_RAW:
+ ret = ltr390_register_read(data, LTR390_UVS_DATA);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info ltr390_info = {
+ .read_raw = ltr390_read_raw,
+};
+
+static const struct iio_chan_spec ltr390_channels[] = {
+ {
+ .type = IIO_UVINDEX,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED)
+ },
+ {
+ .type = IIO_INTENSITY,
+ .channel2 = IIO_MOD_LIGHT_UV,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW)
+ },
+};
+
+static int ltr390_probe(struct i2c_client *client)
+{
+ struct ltr390_data *data;
+ struct iio_dev *indio_dev;
+ int ret, part_number;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+
+ data->regmap = devm_regmap_init_i2c(client, &ltr390_regmap_config);
+ if (IS_ERR(data->regmap))
+ return dev_err_probe(&client->dev, PTR_ERR(data->regmap),
+ "regmap initialization failed\n");
+
+ data->client = client;
+ i2c_set_clientdata(client, indio_dev);
+ mutex_init(&data->lock);
+
+ indio_dev->info = &ltr390_info;
+ indio_dev->channels = ltr390_channels;
+ indio_dev->num_channels = ARRAY_SIZE(ltr390_channels);
+ indio_dev->name = LTR390_DEVICE_NAME;
+
+ ret = regmap_read(data->regmap, LTR390_PART_ID, &part_number);
+ if (ret) {
+ dev_err(&client->dev, "failed to get sensor's part id: %d",
+ ret);
+ return ret;
+ }
+ /* Lower 4 bits of `part_number` change with hardware revisions */
+ if (part_number >> 4 != LTR390_PART_NUMBER_ID) {
+ dev_err(&client->dev, "received invalid product id: 0x%x",
+ part_number);
+ return -ENODEV;
+ }
+ dev_dbg(&client->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) {
+ dev_err(&client->dev, "failed to enable the sensor: %d\n", ret);
+ return ret;
+ }
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id ltr390_id[] = {
+ { LTR390_DEVICE_NAME, 0 },
+ { /* Sentinel */ },
+};
+MODULE_DEVICE_TABLE(i2c, ltr390_id);
+
+static struct i2c_driver ltr390_driver = {
+ .driver = {
+ .name = LTR390_DEVICE_NAME,
+ },
+ .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");
--
2.42.0