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Subject[PATCH v3 1/2] Add driver support for MAX44009 light sensor
The MAX44009 is a low-power ambient light sensor from Maxim
Integrated. It differs from the MAX44000 in that it doesn't have
proximity sensing and that it requires far less current (1 micro-amp
vs 5 micro-amps). The register mapping and feature set between the
two are different enough to require a new driver for the MAX44009.

Developed and tested with a BeagleBone Black and UDOO Neo (i.MX6SX)

Supported features:

* Reading lux (processed value)

* Rising and falling illuminance threshold
events

* Configuring integration time

https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf

Signed-off-by: Robert Eshleman <bobbyeshleman@gmail.com>
---
Changes to v3:
- Remove unnecessary mask when setting integration time
- Return IRQ_NONE in IRQ handler when interrupt not from this device
- Fix incorrect register usage when reading lux low byte
- Clean up style

Changes to v2:
- Remove unnecessary mutex locking
- Remove unnecessary triggered buffer support
- Remove unnecessary wrapper functions for smbus reads and writes
- Remove scale avail support
- Use constant scale to provide processed values instead of raw
- Remove IRQ_NONE return for non-shared IRQ
- Clean up style

drivers/iio/light/Kconfig | 10 +
drivers/iio/light/Makefile | 1 +
drivers/iio/light/max44009.c | 555 +++++++++++++++++++++++++++++++++++
3 files changed, 566 insertions(+)
create mode 100644 drivers/iio/light/max44009.c

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 36f458433480..5190eacfeb0a 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -299,6 +299,16 @@ config MAX44000
To compile this driver as a module, choose M here:
the module will be called max44000.

+config MAX44009
+ tristate "MAX44009 Ambient Light Sensor"
+ depends on I2C
+ help
+ Say Y here if you want to build support for Maxim Integrated's
+ MAX44009 ambient light sensor device.
+
+ To compile this driver as a module, choose M here:
+ the module will be called max44009.
+
config OPT3001
tristate "Texas Instruments OPT3001 Light Sensor"
depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index 286bf3975372..e40794fbb435 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_SENSORS_LM3533) += lm3533-als.o
obj-$(CONFIG_LTR501) += ltr501.o
obj-$(CONFIG_LV0104CS) += lv0104cs.o
obj-$(CONFIG_MAX44000) += max44000.o
+obj-$(CONFIG_MAX44009) += max44009.o
obj-$(CONFIG_OPT3001) += opt3001.o
obj-$(CONFIG_PA12203001) += pa12203001.o
obj-$(CONFIG_RPR0521) += rpr0521.o
diff --git a/drivers/iio/light/max44009.c b/drivers/iio/light/max44009.c
new file mode 100644
index 000000000000..fdbe2b840b02
--- /dev/null
+++ b/drivers/iio/light/max44009.c
@@ -0,0 +1,555 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * max44009.c - Support for MAX44009 Ambient Light Sensor
+ *
+ * Copyright (c) 2019 Robert Eshleman <bobbyeshleman@gmail.com>
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf
+ *
+ * TODO: Support continuous mode and configuring from manual mode to
+ * automatic mode.
+ *
+ * Default I2C address: 0x4a
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/bits.h>
+#include <linux/i2c.h>
+#include <linux/iio/events.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/util_macros.h>
+
+#define MAX44009_DRV_NAME "max44009"
+
+/* Registers in datasheet order */
+#define MAX44009_REG_INT_STATUS 0x0
+#define MAX44009_REG_INT_EN 0x1
+#define MAX44009_REG_CFG 0x2
+#define MAX44009_REG_LUX_HI 0x3
+#define MAX44009_REG_LUX_LO 0x4
+#define MAX44009_REG_UPPER_THR 0x5
+#define MAX44009_REG_LOWER_THR 0x6
+#define MAX44009_REG_THR_TIMER 0x7
+
+#define MAX44009_CFG_TIM_MASK GENMASK(2, 0)
+#define MAX44009_CFG_MAN_MODE_MASK BIT(6)
+
+/* The maximum rising threshold for the max44009 */
+#define MAX44009_MAXIMUM_THRESHOLD 7520256
+
+#define MAX44009_THRESH_EXP_MASK (0xf << 4)
+#define MAX44009_THRESH_EXP_RSHIFT 4
+#define MAX44009_THRESH_MANT_LSHIFT 4
+#define MAX44009_THRESH_MANT_MASK 0xf
+
+#define MAX44009_UPPER_THR_MINIMUM 15
+
+/* The max44009 always scales raw readings by 0.045 and is non-configurable */
+#define MAX44009_SCALE_NUMERATOR 45
+#define MAX44009_SCALE_DENOMINATOR 1000
+
+/* The fixed-point fractional multiplier for de-scaling threshold values */
+#define MAX44009_FRACT_MULT 1000000
+
+static const u32 max44009_int_time_ns_array[] = {
+ 800000000,
+ 400000000,
+ 200000000,
+ 100000000,
+ 50000000, /* Manual mode only */
+ 25000000, /* Manual mode only */
+ 12500000, /* Manual mode only */
+ 6250000, /* Manual mode only */
+};
+
+static const char max44009_int_time_str[] =
+ "0.8 "
+ "0.4 "
+ "0.2 "
+ "0.1 "
+ "0.05 "
+ "0.025 "
+ "0.0125 "
+ "0.00625";
+
+struct max44009_data {
+ struct i2c_client *client;
+ struct mutex lock;
+};
+
+static const struct iio_event_spec max44009_event_spec[] = {
+ {
+ .type = IIO_EV_TYPE_THRESH,
+ .dir = IIO_EV_DIR_RISING,
+ .mask_separate = BIT(IIO_EV_INFO_VALUE) |
+ BIT(IIO_EV_INFO_ENABLE),
+ },
+ {
+ .type = IIO_EV_TYPE_THRESH,
+ .dir = IIO_EV_DIR_FALLING,
+ .mask_separate = BIT(IIO_EV_INFO_VALUE) |
+ BIT(IIO_EV_INFO_ENABLE),
+ },
+};
+
+static const struct iio_chan_spec max44009_channels[] = {
+ {
+ .type = IIO_LIGHT,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+ BIT(IIO_CHAN_INFO_INT_TIME),
+ .event_spec = max44009_event_spec,
+ .num_event_specs = ARRAY_SIZE(max44009_event_spec),
+ },
+};
+
+static int max44009_read_int_time(struct max44009_data *data)
+{
+
+ int ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_CFG);
+
+ if (ret < 0)
+ return ret;
+
+ return max44009_int_time_ns_array[ret & MAX44009_CFG_TIM_MASK];
+}
+
+static int max44009_write_int_time(struct max44009_data *data,
+ int val, int val2)
+{
+ struct i2c_client *client = data->client;
+ int ret, int_time, config;
+ s64 ns;
+
+ ns = val * NSEC_PER_SEC + val2;
+ int_time = find_closest_descending(
+ ns,
+ max44009_int_time_ns_array,
+ ARRAY_SIZE(max44009_int_time_ns_array));
+
+ ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
+ if (ret < 0)
+ return ret;
+
+ config = ret;
+ config &= int_time;
+
+ /*
+ * To set the integration time, the device must also be in manual
+ * mode.
+ */
+ config |= MAX44009_CFG_MAN_MODE_MASK;
+
+ return i2c_smbus_write_byte_data(client, MAX44009_REG_CFG, config);
+}
+
+static int max44009_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int val,
+ int val2, long mask)
+{
+ struct max44009_data *data = iio_priv(indio_dev);
+ int ret;
+
+ if (mask == IIO_CHAN_INFO_INT_TIME && chan->type == IIO_LIGHT) {
+ mutex_lock(&data->lock);
+ ret = max44009_write_int_time(data, val, val2);
+ mutex_unlock(&data->lock);
+ return ret;
+ }
+ return -EINVAL;
+}
+
+static int max44009_write_raw_get_fmt(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ long mask)
+{
+ return IIO_VAL_INT_PLUS_NANO;
+}
+
+static int max44009_lux_raw(u8 hi, u8 lo)
+{
+ int mantissa;
+ int exponent;
+
+ /*
+ * The mantissa consists of the low nibble of the Lux High Byte
+ * and the low nibble of the Lux Low Byte.
+ */
+ mantissa = ((hi & 0xf) << 4) | (lo & 0xf);
+
+ /* The exponent byte is just the upper nibble of the Lux High Byte */
+ exponent = (hi >> 4) & 0xf;
+
+ /*
+ * The exponent value is base 2 to the power of the raw exponent byte.
+ */
+ exponent = 1 << exponent;
+
+ return exponent * mantissa;
+}
+
+#define MAX44009_READ_LUX_XFER_LEN (4)
+
+static int max44009_read_lux_raw(struct max44009_data *data)
+{
+ int ret;
+ u8 hireg = MAX44009_REG_LUX_HI;
+ u8 loreg = MAX44009_REG_LUX_LO;
+ u8 lo = 0;
+ u8 hi = 0;
+
+ struct i2c_msg msgs[] = {
+ {
+ .addr = data->client->addr,
+ .flags = 0,
+ .len = sizeof(hireg),
+ .buf = &hireg,
+ },
+ {
+ .addr = data->client->addr,
+ .flags = I2C_M_RD,
+ .len = sizeof(hi),
+ .buf = &hi,
+ },
+ {
+ .addr = data->client->addr,
+ .flags = 0,
+ .len = sizeof(loreg),
+ .buf = &loreg,
+ },
+ {
+ .addr = data->client->addr,
+ .flags = I2C_M_RD,
+ .len = sizeof(lo),
+ .buf = &lo,
+ }
+ };
+
+ /*
+ * Use i2c_transfer instead of smbus read because i2c_transfer
+ * does NOT use a stop bit between address write and data read.
+ * Using a stop bit causes disjoint upper/lower byte reads and
+ * reduces accuracy.
+ */
+ ret = i2c_transfer(data->client->adapter,
+ msgs, MAX44009_READ_LUX_XFER_LEN);
+
+ if (ret != MAX44009_READ_LUX_XFER_LEN)
+ return -EIO;
+
+ return max44009_lux_raw(hi, lo);
+}
+
+static int max44009_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long mask)
+{
+ struct max44009_data *data = iio_priv(indio_dev);
+ int lux_raw;
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_PROCESSED:
+ switch (chan->type) {
+ case IIO_LIGHT:
+ ret = max44009_read_lux_raw(data);
+ if (ret < 0)
+ return ret;
+ lux_raw = ret;
+
+ *val = lux_raw * MAX44009_SCALE_NUMERATOR;
+ *val2 = MAX44009_SCALE_DENOMINATOR;
+ return IIO_VAL_FRACTIONAL;
+ default:
+ return -EINVAL;
+ }
+ case IIO_CHAN_INFO_INT_TIME:
+ switch (chan->type) {
+ case IIO_LIGHT:
+ ret = max44009_read_int_time(data);
+ if (ret < 0)
+ return ret;
+
+ *val2 = ret;
+ *val = 0;
+ return IIO_VAL_INT_PLUS_NANO;
+ default:
+ return -EINVAL;
+ }
+ default:
+ return -EINVAL;
+ }
+}
+
+static IIO_CONST_ATTR(illuminance_integration_time_available,
+ max44009_int_time_str);
+
+static struct attribute *max44009_attributes[] = {
+ &iio_const_attr_illuminance_integration_time_available.dev_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group max44009_attribute_group = {
+ .attrs = max44009_attributes,
+};
+
+static int max44009_threshold_byte_from_fraction(int integral, int fractional)
+{
+ int mantissa, exp;
+
+ if ((integral <= 0 && fractional <= 0) ||
+ integral > MAX44009_MAXIMUM_THRESHOLD ||
+ (integral == MAX44009_MAXIMUM_THRESHOLD && fractional != 0))
+ return -EINVAL;
+
+ /* Reverse scaling of fixed-point integral */
+ mantissa = integral * MAX44009_SCALE_DENOMINATOR;
+ mantissa /= MAX44009_SCALE_NUMERATOR;
+
+ /* Reverse scaling of fixed-point fractional */
+ mantissa += fractional / MAX44009_FRACT_MULT *
+ (MAX44009_SCALE_DENOMINATOR / MAX44009_SCALE_NUMERATOR);
+
+ for (exp = 0; mantissa > 0xff; exp++)
+ mantissa >>= 1;
+
+ mantissa >>= 4;
+ mantissa &= 0xf;
+ exp <<= 4;
+
+ return exp | mantissa;
+}
+
+static int max44009_get_thr_reg(enum iio_event_direction dir)
+{
+ switch (dir) {
+ case IIO_EV_DIR_RISING:
+ return MAX44009_REG_UPPER_THR;
+ case IIO_EV_DIR_FALLING:
+ return MAX44009_REG_LOWER_THR;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int max44009_write_event_value(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir,
+ enum iio_event_info info,
+ int val, int val2)
+{
+ struct max44009_data *data = iio_priv(indio_dev);
+ int reg, threshold;
+
+ if (info != IIO_EV_INFO_VALUE || chan->type != IIO_LIGHT)
+ return -EINVAL;
+
+ threshold = max44009_threshold_byte_from_fraction(val, val2);
+ if (threshold < 0)
+ return threshold;
+
+ reg = max44009_get_thr_reg(dir);
+ if (reg < 0)
+ return reg;
+
+ return i2c_smbus_write_byte_data(data->client, reg, threshold);
+}
+
+static int max44009_read_threshold(struct iio_dev *indio_dev,
+ enum iio_event_direction dir)
+{
+ struct max44009_data *data = iio_priv(indio_dev);
+ int byte, reg;
+ int mantissa, exponent;
+
+ reg = max44009_get_thr_reg(dir);
+ if (reg < 0)
+ return reg;
+
+ byte = i2c_smbus_read_byte_data(data->client, reg);
+ if (byte < 0)
+ return byte;
+
+ mantissa = byte & MAX44009_THRESH_MANT_MASK;
+ mantissa <<= MAX44009_THRESH_MANT_LSHIFT;
+
+ /*
+ * To get the upper threshold, always adds the minimum upper threshold
+ * value to the shifted byte value (see datasheet).
+ */
+ if (dir == IIO_EV_DIR_RISING)
+ mantissa += MAX44009_UPPER_THR_MINIMUM;
+
+ /*
+ * Exponent is base 2 to the power of the threshold exponent byte
+ * value
+ */
+ exponent = byte & MAX44009_THRESH_EXP_MASK;
+ exponent >>= MAX44009_THRESH_EXP_RSHIFT;
+
+ return (1 << exponent) * mantissa;
+}
+
+static int max44009_read_event_value(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir,
+ enum iio_event_info info,
+ int *val, int *val2)
+{
+ int ret;
+ int threshold;
+
+ if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
+ return -EINVAL;
+
+ ret = max44009_read_threshold(indio_dev, dir);
+ if (ret < 0)
+ return ret;
+ threshold = ret;
+
+ *val = threshold * MAX44009_SCALE_NUMERATOR;
+ *val2 = MAX44009_SCALE_DENOMINATOR;
+
+ return IIO_VAL_FRACTIONAL;
+}
+
+static int max44009_write_event_config(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir,
+ int state)
+{
+ struct max44009_data *data = iio_priv(indio_dev);
+ int ret;
+
+ if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
+ return -EINVAL;
+
+ ret = i2c_smbus_write_byte_data(data->client,
+ MAX44009_REG_INT_EN, state);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * Set device to trigger interrupt immediately upon exceeding
+ * the threshold limit.
+ */
+ return i2c_smbus_write_byte_data(data->client,
+ MAX44009_REG_THR_TIMER, 0);
+}
+
+static int max44009_read_event_config(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ enum iio_event_type type,
+ enum iio_event_direction dir)
+{
+ struct max44009_data *data = iio_priv(indio_dev);
+
+ if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
+ return -EINVAL;
+
+ return i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_EN);
+}
+
+static const struct iio_info max44009_info = {
+ .read_raw = max44009_read_raw,
+ .write_raw = max44009_write_raw,
+ .write_raw_get_fmt = max44009_write_raw_get_fmt,
+ .read_event_value = max44009_read_event_value,
+ .read_event_config = max44009_read_event_config,
+ .write_event_value = max44009_write_event_value,
+ .write_event_config = max44009_write_event_config,
+ .attrs = &max44009_attribute_group,
+};
+
+static irqreturn_t max44009_threaded_irq_handler(int irq, void *p)
+{
+ struct iio_dev *indio_dev = p;
+ struct max44009_data *data = iio_priv(indio_dev);
+ int ret;
+
+ ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_STATUS);
+ if (ret) {
+ iio_push_event(indio_dev,
+ IIO_UNMOD_EVENT_CODE(IIO_LIGHT, 0,
+ IIO_EV_TYPE_THRESH,
+ IIO_EV_DIR_EITHER),
+ iio_get_time_ns(indio_dev));
+
+ return IRQ_HANDLED;
+ }
+
+ return IRQ_NONE;
+}
+
+static int max44009_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct max44009_data *data;
+ struct iio_dev *indio_dev;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ data = iio_priv(indio_dev);
+ i2c_set_clientdata(client, indio_dev);
+ data->client = client;
+ indio_dev->dev.parent = &client->dev;
+ indio_dev->info = &max44009_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->name = MAX44009_DRV_NAME;
+ indio_dev->channels = max44009_channels;
+ indio_dev->num_channels = ARRAY_SIZE(max44009_channels);
+ mutex_init(&data->lock);
+
+ /* Clear any stale interrupt bit */
+ ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
+ if (ret < 0)
+ return ret;
+
+ if (client->irq > 0) {
+ ret = devm_request_threaded_irq(&client->dev, client->irq,
+ NULL,
+ max44009_threaded_irq_handler,
+ IRQF_TRIGGER_FALLING |
+ IRQF_ONESHOT | IRQF_SHARED,
+ "max44009_event",
+ indio_dev);
+ if (ret < 0)
+ return ret;
+ }
+
+ return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id max44009_id[] = {
+ { "max44009", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, max44009_id);
+
+static struct i2c_driver max44009_driver = {
+ .driver = {
+ .name = MAX44009_DRV_NAME,
+ },
+ .probe = max44009_probe,
+ .id_table = max44009_id,
+};
+module_i2c_driver(max44009_driver);
+
+static const struct of_device_id max44009_of_match[] = {
+ { .compatible = "maxim,max44009" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, max44009_of_match);
+
+MODULE_AUTHOR("Robert Eshleman <bobbyeshleman@gmail.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("MAX44009 ambient light sensor driver");
--
2.20.1
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