/*
 * MAX44000 Ambient and Infrared Proximity Sensor
 *
 * Copyright (c) 2016, Intel Corporation.
 *
 * This file is subject to the terms and conditions of version 2 of
 * the GNU General Public License.  See the file COPYING in the main
 * directory of this archive for more details.
 *
 * Data sheet: https://datasheets.maximintegrated.com/en/ds/MAX44000.pdf
 *
 * 7-bit I2C slave address 0x4a
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/regmap.h>
#include <linux/util_macros.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/acpi.h>

#define MAX44000_DRV_NAME               "max44000"

/* Registers in datasheet order */
#define MAX44000_REG_STATUS             0x00
#define MAX44000_REG_CFG_MAIN           0x01
#define MAX44000_REG_CFG_RX             0x02
#define MAX44000_REG_CFG_TX             0x03
#define MAX44000_REG_ALS_DATA_HI        0x04
#define MAX44000_REG_ALS_DATA_LO        0x05
#define MAX44000_REG_PRX_DATA           0x16
#define MAX44000_REG_ALS_UPTHR_HI       0x06
#define MAX44000_REG_ALS_UPTHR_LO       0x07
#define MAX44000_REG_ALS_LOTHR_HI       0x08
#define MAX44000_REG_ALS_LOTHR_LO       0x09
#define MAX44000_REG_PST                0x0a
#define MAX44000_REG_PRX_IND            0x0b
#define MAX44000_REG_PRX_THR            0x0c
#define MAX44000_REG_TRIM_GAIN_GREEN    0x0f
#define MAX44000_REG_TRIM_GAIN_IR       0x10

/* REG_CFG bits */
#define MAX44000_CFG_ALSINTE            0x01
#define MAX44000_CFG_PRXINTE            0x02
#define MAX44000_CFG_MASK               0x1c
#define MAX44000_CFG_MODE_SHUTDOWN      0x00
#define MAX44000_CFG_MODE_ALS_GIR       0x04
#define MAX44000_CFG_MODE_ALS_G         0x08
#define MAX44000_CFG_MODE_ALS_IR        0x0c
#define MAX44000_CFG_MODE_ALS_PRX       0x10
#define MAX44000_CFG_MODE_PRX           0x14
#define MAX44000_CFG_TRIM               0x20

/*
 * Upper 4 bits are not documented but start as 1 on powerup
 * Setting them to 0 causes proximity to misbehave so set them to 1
 */
#define MAX44000_REG_CFG_RX_DEFAULT 0xf0

/* REG_RX bits */
#define MAX44000_CFG_RX_ALSTIM_MASK     0x0c
#define MAX44000_CFG_RX_ALSTIM_SHIFT    2
#define MAX44000_CFG_RX_ALSPGA_MASK     0x03
#define MAX44000_CFG_RX_ALSPGA_SHIFT    0

/* REG_TX bits */
#define MAX44000_LED_CURRENT_MASK       0xf
#define MAX44000_LED_CURRENT_MAX        11
#define MAX44000_LED_CURRENT_DEFAULT    6

#define MAX44000_ALSDATA_OVERFLOW       0x4000

struct max44000_data {
        struct mutex lock;
        struct regmap *regmap;
};

/* Default scale is set to the minimum of 0.03125 or 1 / (1 << 5) lux */
#define MAX44000_ALS_TO_LUX_DEFAULT_FRACTION_LOG2 5

/* Scale can be multiplied by up to 128x via ALSPGA for measurement gain */
static const int max44000_alspga_shift[] = {0, 2, 4, 7};
#define MAX44000_ALSPGA_MAX_SHIFT 7

/*
 * Scale can be multiplied by up to 64x via ALSTIM because of lost resolution
 *
 * This scaling factor is hidden from userspace and instead accounted for when
 * reading raw values from the device.
 *
 * This makes it possible to cleanly expose ALSPGA as IIO_CHAN_INFO_SCALE and
 * ALSTIM as IIO_CHAN_INFO_INT_TIME without the values affecting each other.
 *
 * Handling this internally is also required for buffer support because the
 * channel's scan_type can't be modified dynamically.
 */
static const int max44000_alstim_shift[] = {0, 2, 4, 6};
#define MAX44000_ALSTIM_SHIFT(alstim) (2 * (alstim))

/* Available integration times with pretty manual alignment: */
static const int max44000_int_time_avail_ns_array[] = {
           100000000,
            25000000,
             6250000,
             1562500,
};
static const char max44000_int_time_avail_str[] =
        "0.100 "
        "0.025 "
        "0.00625 "
        "0.001625";

/* Available scales (internal to ulux) with pretty manual alignment: */
static const int max44000_scale_avail_ulux_array[] = {
            31250,
           125000,
           500000,
          4000000,
};
static const char max44000_scale_avail_str[] =
        "0.03125 "
        "0.125 "
        "0.5 "
         "4";

#define MAX44000_SCAN_INDEX_ALS 0
#define MAX44000_SCAN_INDEX_PRX 1

static const struct iio_chan_spec max44000_channels[] = {
        {
                .type = IIO_LIGHT,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
                                            BIT(IIO_CHAN_INFO_INT_TIME),
                .scan_index = MAX44000_SCAN_INDEX_ALS,
                .scan_type = {
                        .sign           = 'u',
                        .realbits       = 14,
                        .storagebits    = 16,
                }
        },
        {
                .type = IIO_PROXIMITY,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .scan_index = MAX44000_SCAN_INDEX_PRX,
                .scan_type = {
                        .sign           = 'u',
                        .realbits       = 8,
                        .storagebits    = 16,
                }
        },
        IIO_CHAN_SOFT_TIMESTAMP(2),
        {
                .type = IIO_CURRENT,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                                      BIT(IIO_CHAN_INFO_SCALE),
                .extend_name = "led",
                .output = 1,
                .scan_index = -1,
        },
};

static int max44000_read_alstim(struct max44000_data *data)
{
        unsigned int val;
        int ret;

        ret = regmap_read(data->regmap, MAX44000_REG_CFG_RX, &val);
        if (ret < 0)
                return ret;
        return (val & MAX44000_CFG_RX_ALSTIM_MASK) >> MAX44000_CFG_RX_ALSTIM_SHIFT;
}

static int max44000_write_alstim(struct max44000_data *data, int val)
{
        return regmap_write_bits(data->regmap, MAX44000_REG_CFG_RX,
                                 MAX44000_CFG_RX_ALSTIM_MASK,
                                 val << MAX44000_CFG_RX_ALSTIM_SHIFT);
}

static int max44000_read_alspga(struct max44000_data *data)
{
        unsigned int val;
        int ret;

        ret = regmap_read(data->regmap, MAX44000_REG_CFG_RX, &val);
        if (ret < 0)
                return ret;
        return (val & MAX44000_CFG_RX_ALSPGA_MASK) >> MAX44000_CFG_RX_ALSPGA_SHIFT;
}

static int max44000_write_alspga(struct max44000_data *data, int val)
{
        return regmap_write_bits(data->regmap, MAX44000_REG_CFG_RX,
                                 MAX44000_CFG_RX_ALSPGA_MASK,
                                 val << MAX44000_CFG_RX_ALSPGA_SHIFT);
}

static int max44000_read_alsval(struct max44000_data *data)
{
        u16 regval;
        int alstim, ret;

        ret = regmap_bulk_read(data->regmap, MAX44000_REG_ALS_DATA_HI,
                               &regval, sizeof(regval));
        if (ret < 0)
                return ret;
        alstim = ret = max44000_read_alstim(data);
        if (ret < 0)
                return ret;

        regval = be16_to_cpu(regval);

        /*
         * Overflow is explained on datasheet page 17.
         *
         * It's a warning that either the G or IR channel has become saturated
         * and that the value in the register is likely incorrect.
         *
         * The recommendation is to change the scale (ALSPGA).
         * The driver just returns the max representable value.
         */
        if (regval & MAX44000_ALSDATA_OVERFLOW)
                return 0x3FFF;

        return regval << MAX44000_ALSTIM_SHIFT(alstim);
}

static int max44000_write_led_current_raw(struct max44000_data *data, int val)
{
        /* Maybe we should clamp the value instead? */
        if (val < 0 || val > MAX44000_LED_CURRENT_MAX)
                return -ERANGE;
        if (val >= 8)
                val += 4;
        return regmap_write_bits(data->regmap, MAX44000_REG_CFG_TX,
                                 MAX44000_LED_CURRENT_MASK, val);
}

static int max44000_read_led_current_raw(struct max44000_data *data)
{
        unsigned int regval;
        int ret;

        ret = regmap_read(data->regmap, MAX44000_REG_CFG_TX, &regval);
        if (ret < 0)
                return ret;
        regval &= MAX44000_LED_CURRENT_MASK;
        if (regval >= 8)
                regval -= 4;
        return regval;
}

static int max44000_read_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan,
                             int *val, int *val2, long mask)
{
        struct max44000_data *data = iio_priv(indio_dev);
        int alstim, alspga;
        unsigned int regval;
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                switch (chan->type) {
                case IIO_LIGHT:
                        mutex_lock(&data->lock);
                        ret = max44000_read_alsval(data);
                        mutex_unlock(&data->lock);
                        if (ret < 0)
                                return ret;
                        *val = ret;
                        return IIO_VAL_INT;

                case IIO_PROXIMITY:
                        mutex_lock(&data->lock);
                        ret = regmap_read(data->regmap, MAX44000_REG_PRX_DATA, &regval);
                        mutex_unlock(&data->lock);
                        if (ret < 0)
                                return ret;
                        *val = regval;
                        return IIO_VAL_INT;

                case IIO_CURRENT:
                        mutex_lock(&data->lock);
                        ret = max44000_read_led_current_raw(data);
                        mutex_unlock(&data->lock);
                        if (ret < 0)
                                return ret;
                        *val = ret;
                        return IIO_VAL_INT;

                default:
                        return -EINVAL;
                }

        case IIO_CHAN_INFO_SCALE:
                switch (chan->type) {
                case IIO_CURRENT:
                        /* Output register is in 10s of miliamps */
                        *val = 10;
                        return IIO_VAL_INT;

                case IIO_LIGHT:
                        mutex_lock(&data->lock);
                        alspga = ret = max44000_read_alspga(data);
                        mutex_unlock(&data->lock);
                        if (ret < 0)
                                return ret;

                        /* Avoid negative shifts */
                        *val = (1 << MAX44000_ALSPGA_MAX_SHIFT);
                        *val2 = MAX44000_ALS_TO_LUX_DEFAULT_FRACTION_LOG2
                                        + MAX44000_ALSPGA_MAX_SHIFT
                                        - max44000_alspga_shift[alspga];
                        return IIO_VAL_FRACTIONAL_LOG2;

                default:
                        return -EINVAL;
                }

        case IIO_CHAN_INFO_INT_TIME:
                mutex_lock(&data->lock);
                alstim = ret = max44000_read_alstim(data);
                mutex_unlock(&data->lock);

                if (ret < 0)
                        return ret;
                *val = 0;
                *val2 = max44000_int_time_avail_ns_array[alstim];
                return IIO_VAL_INT_PLUS_NANO;

        default:
                return -EINVAL;
        }
}

static int max44000_write_raw(struct iio_dev *indio_dev,
                              struct iio_chan_spec const *chan,
                              int val, int val2, long mask)
{
        struct max44000_data *data = iio_priv(indio_dev);
        int ret;

        if (mask == IIO_CHAN_INFO_RAW && chan->type == IIO_CURRENT) {
                mutex_lock(&data->lock);
                ret = max44000_write_led_current_raw(data, val);
                mutex_unlock(&data->lock);
                return ret;
        } else if (mask == IIO_CHAN_INFO_INT_TIME && chan->type == IIO_LIGHT) {
                s64 valns = val * NSEC_PER_SEC + val2;
                int alstim = find_closest_descending(valns,
                                max44000_int_time_avail_ns_array,
                                ARRAY_SIZE(max44000_int_time_avail_ns_array));
                mutex_lock(&data->lock);
                ret = max44000_write_alstim(data, alstim);
                mutex_unlock(&data->lock);
                return ret;
        } else if (mask == IIO_CHAN_INFO_SCALE && chan->type == IIO_LIGHT) {
                s64 valus = val * USEC_PER_SEC + val2;
                int alspga = find_closest(valus,
                                max44000_scale_avail_ulux_array,
                                ARRAY_SIZE(max44000_scale_avail_ulux_array));
                mutex_lock(&data->lock);
                ret = max44000_write_alspga(data, alspga);
                mutex_unlock(&data->lock);
                return ret;
        }

        return -EINVAL;
}

static int max44000_write_raw_get_fmt(struct iio_dev *indio_dev,
                                      struct iio_chan_spec const *chan,
                                      long mask)
{
        if (mask == IIO_CHAN_INFO_INT_TIME && chan->type == IIO_LIGHT)
                return IIO_VAL_INT_PLUS_NANO;
        else if (mask == IIO_CHAN_INFO_SCALE && chan->type == IIO_LIGHT)
                return IIO_VAL_INT_PLUS_MICRO;
        else
                return IIO_VAL_INT;
}

static IIO_CONST_ATTR(illuminance_integration_time_available, max44000_int_time_avail_str);
static IIO_CONST_ATTR(illuminance_scale_available, max44000_scale_avail_str);

static struct attribute *max44000_attributes[] = {
        &iio_const_attr_illuminance_integration_time_available.dev_attr.attr,
        &iio_const_attr_illuminance_scale_available.dev_attr.attr,
        NULL
};

static const struct attribute_group max44000_attribute_group = {
        .attrs = max44000_attributes,
};

static const struct iio_info max44000_info = {
        .driver_module          = THIS_MODULE,
        .read_raw               = max44000_read_raw,
        .write_raw              = max44000_write_raw,
        .write_raw_get_fmt      = max44000_write_raw_get_fmt,
        .attrs                  = &max44000_attribute_group,
};

static bool max44000_readable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case MAX44000_REG_STATUS:
        case MAX44000_REG_CFG_MAIN:
        case MAX44000_REG_CFG_RX:
        case MAX44000_REG_CFG_TX:
        case MAX44000_REG_ALS_DATA_HI:
        case MAX44000_REG_ALS_DATA_LO:
        case MAX44000_REG_PRX_DATA:
        case MAX44000_REG_ALS_UPTHR_HI:
        case MAX44000_REG_ALS_UPTHR_LO:
        case MAX44000_REG_ALS_LOTHR_HI:
        case MAX44000_REG_ALS_LOTHR_LO:
        case MAX44000_REG_PST:
        case MAX44000_REG_PRX_IND:
        case MAX44000_REG_PRX_THR:
        case MAX44000_REG_TRIM_GAIN_GREEN:
        case MAX44000_REG_TRIM_GAIN_IR:
                return true;
        default:
                return false;
        }
}

static bool max44000_writeable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case MAX44000_REG_CFG_MAIN:
        case MAX44000_REG_CFG_RX:
        case MAX44000_REG_CFG_TX:
        case MAX44000_REG_ALS_UPTHR_HI:
        case MAX44000_REG_ALS_UPTHR_LO:
        case MAX44000_REG_ALS_LOTHR_HI:
        case MAX44000_REG_ALS_LOTHR_LO:
        case MAX44000_REG_PST:
        case MAX44000_REG_PRX_IND:
        case MAX44000_REG_PRX_THR:
        case MAX44000_REG_TRIM_GAIN_GREEN:
        case MAX44000_REG_TRIM_GAIN_IR:
                return true;
        default:
                return false;
        }
}

static bool max44000_volatile_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case MAX44000_REG_STATUS:
        case MAX44000_REG_ALS_DATA_HI:
        case MAX44000_REG_ALS_DATA_LO:
        case MAX44000_REG_PRX_DATA:
                return true;
        default:
                return false;
        }
}

static bool max44000_precious_reg(struct device *dev, unsigned int reg)
{
        return reg == MAX44000_REG_STATUS;
}

static const struct regmap_config max44000_regmap_config = {
        .reg_bits       = 8,
        .val_bits       = 8,

        .max_register   = MAX44000_REG_PRX_DATA,
        .readable_reg   = max44000_readable_reg,
        .writeable_reg  = max44000_writeable_reg,
        .volatile_reg   = max44000_volatile_reg,
        .precious_reg   = max44000_precious_reg,

        .use_single_rw  = 1,
        .cache_type     = REGCACHE_RBTREE,
};

static irqreturn_t max44000_trigger_handler(int irq, void *p)
{
        struct iio_poll_func *pf = p;
        struct iio_dev *indio_dev = pf->indio_dev;
        struct max44000_data *data = iio_priv(indio_dev);
        u16 buf[8]; /* 2x u16 + padding + 8 bytes timestamp */
        int index = 0;
        unsigned int regval;
        int ret;

        mutex_lock(&data->lock);
        if (test_bit(MAX44000_SCAN_INDEX_ALS, indio_dev->active_scan_mask)) {
                ret = max44000_read_alsval(data);
                if (ret < 0)
                        goto out_unlock;
                buf[index++] = ret;
        }
        if (test_bit(MAX44000_SCAN_INDEX_PRX, indio_dev->active_scan_mask)) {
                ret = regmap_read(data->regmap, MAX44000_REG_PRX_DATA, &regval);
                if (ret < 0)
                        goto out_unlock;
                buf[index] = regval;
        }
        mutex_unlock(&data->lock);

        iio_push_to_buffers_with_timestamp(indio_dev, buf,
                                           iio_get_time_ns(indio_dev));
        iio_trigger_notify_done(indio_dev->trig);
        return IRQ_HANDLED;

out_unlock:
        mutex_unlock(&data->lock);
        iio_trigger_notify_done(indio_dev->trig);
        return IRQ_HANDLED;
}

static int max44000_probe(struct i2c_client *client,
                          const struct i2c_device_id *id)
{
        struct max44000_data *data;
        struct iio_dev *indio_dev;
        int ret, reg;

        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, &max44000_regmap_config);
        if (IS_ERR(data->regmap)) {
                dev_err(&client->dev, "regmap_init failed!\n");
                return PTR_ERR(data->regmap);
        }

        i2c_set_clientdata(client, indio_dev);
        mutex_init(&data->lock);
        indio_dev->dev.parent = &client->dev;
        indio_dev->info = &max44000_info;
        indio_dev->name = MAX44000_DRV_NAME;
        indio_dev->channels = max44000_channels;
        indio_dev->num_channels = ARRAY_SIZE(max44000_channels);

        /*
         * The device doesn't have a reset function so we just clear some
         * important bits at probe time to ensure sane operation.
         *
         * Since we don't support interrupts/events the threshold values are
         * not important. We also don't touch trim values.
         */

        /* Reset ALS scaling bits */
        ret = regmap_write(data->regmap, MAX44000_REG_CFG_RX,
                           MAX44000_REG_CFG_RX_DEFAULT);
        if (ret < 0) {
                dev_err(&client->dev, "failed to write default CFG_RX: %d\n",
                        ret);
                return ret;
        }

        /*
         * By default the LED pulse used for the proximity sensor is disabled.
         * Set a middle value so that we get some sort of valid data by default.
         */
        ret = max44000_write_led_current_raw(data, MAX44000_LED_CURRENT_DEFAULT);
        if (ret < 0) {
                dev_err(&client->dev, "failed to write init config: %d\n", ret);
                return ret;
        }

        /* Reset CFG bits to ALS_PRX mode which allows easy reading of both values. */
        reg = MAX44000_CFG_TRIM | MAX44000_CFG_MODE_ALS_PRX;
        ret = regmap_write(data->regmap, MAX44000_REG_CFG_MAIN, reg);
        if (ret < 0) {
                dev_err(&client->dev, "failed to write init config: %d\n", ret);
                return ret;
        }

        /* Read status at least once to clear any stale interrupt bits. */
        ret = regmap_read(data->regmap, MAX44000_REG_STATUS, &reg);
        if (ret < 0) {
                dev_err(&client->dev, "failed to read init status: %d\n", ret);
                return ret;
        }

        ret = iio_triggered_buffer_setup(indio_dev, NULL, max44000_trigger_handler, NULL);
        if (ret < 0) {
                dev_err(&client->dev, "iio triggered buffer setup failed\n");
                return ret;
        }

        return iio_device_register(indio_dev);
}

static int max44000_remove(struct i2c_client *client)
{
        struct iio_dev *indio_dev = i2c_get_clientdata(client);

        iio_device_unregister(indio_dev);
        iio_triggered_buffer_cleanup(indio_dev);

        return 0;
}

static const struct i2c_device_id max44000_id[] = {
        {"max44000", 0},
        { }
};
MODULE_DEVICE_TABLE(i2c, max44000_id);

#ifdef CONFIG_ACPI
static const struct acpi_device_id max44000_acpi_match[] = {
        {"MAX44000", 0},
        { }
};
MODULE_DEVICE_TABLE(acpi, max44000_acpi_match);
#endif

static struct i2c_driver max44000_driver = {
        .driver = {
                .name   = MAX44000_DRV_NAME,
                .acpi_match_table = ACPI_PTR(max44000_acpi_match),
        },
        .probe          = max44000_probe,
        .remove         = max44000_remove,
        .id_table       = max44000_id,
};

module_i2c_driver(max44000_driver);

MODULE_AUTHOR("Crestez Dan Leonard <leonard.crestez@intel.com>");
MODULE_DESCRIPTION("MAX44000 Ambient and Infrared Proximity Sensor");
MODULE_LICENSE("GPL v2");