// SPDX-License-Identifier: GPL-2.0+
// Copyright IBM Corp 2019
/*
 * The DPS310 is a barometric pressure and temperature sensor.
 * Currently only reading a single temperature is supported by
 * this driver.
 *
 * https://www.infineon.com/dgdl/?fileId=5546d462576f34750157750826c42242
 *
 * Temperature calculation:
 *   c0 * 0.5 + c1 * T_raw / kT °C
 *
 * TODO:
 *  - Optionally support the FIFO
 */

#include <linux/i2c.h>
#include <linux/limits.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/regmap.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

#define DPS310_DEV_NAME         "dps310"

#define DPS310_PRS_B0           0x00
#define DPS310_PRS_B1           0x01
#define DPS310_PRS_B2           0x02
#define DPS310_TMP_B0           0x03
#define DPS310_TMP_B1           0x04
#define DPS310_TMP_B2           0x05
#define DPS310_PRS_CFG          0x06
#define  DPS310_PRS_RATE_BITS   GENMASK(6, 4)
#define  DPS310_PRS_PRC_BITS    GENMASK(3, 0)
#define DPS310_TMP_CFG          0x07
#define  DPS310_TMP_RATE_BITS   GENMASK(6, 4)
#define  DPS310_TMP_PRC_BITS    GENMASK(3, 0)
#define  DPS310_TMP_EXT         BIT(7)
#define DPS310_MEAS_CFG         0x08
#define  DPS310_MEAS_CTRL_BITS  GENMASK(2, 0)
#define   DPS310_PRS_EN         BIT(0)
#define   DPS310_TEMP_EN        BIT(1)
#define   DPS310_BACKGROUND     BIT(2)
#define  DPS310_PRS_RDY         BIT(4)
#define  DPS310_TMP_RDY         BIT(5)
#define  DPS310_SENSOR_RDY      BIT(6)
#define  DPS310_COEF_RDY        BIT(7)
#define DPS310_CFG_REG          0x09
#define  DPS310_INT_HL          BIT(7)
#define  DPS310_TMP_SHIFT_EN    BIT(3)
#define  DPS310_PRS_SHIFT_EN    BIT(4)
#define  DPS310_FIFO_EN         BIT(5)
#define  DPS310_SPI_EN          BIT(6)
#define DPS310_RESET            0x0c
#define  DPS310_RESET_MAGIC     0x09
#define DPS310_COEF_BASE        0x10

/* Make sure sleep time is <= 20ms for usleep_range */
#define DPS310_POLL_SLEEP_US(t)         min(20000, (t) / 8)
/* Silently handle error in rate value here */
#define DPS310_POLL_TIMEOUT_US(rc)      ((rc) <= 0 ? 1000000 : 1000000 / (rc))

#define DPS310_PRS_BASE         DPS310_PRS_B0
#define DPS310_TMP_BASE         DPS310_TMP_B0

/*
 * These values (defined in the spec) indicate how to scale the raw register
 * values for each level of precision available.
 */
static const int scale_factors[] = {
         524288,
        1572864,
        3670016,
        7864320,
         253952,
         516096,
        1040384,
        2088960,
};

struct dps310_data {
        struct i2c_client *client;
        struct regmap *regmap;
        struct mutex lock;      /* Lock for sequential HW access functions */

        s32 c0, c1;
        s32 c00, c10, c20, c30, c01, c11, c21;
        s32 pressure_raw;
        s32 temp_raw;
};

static const struct iio_chan_spec dps310_channels[] = {
        {
                .type = IIO_TEMP,
                .info_mask_separate = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
                        BIT(IIO_CHAN_INFO_SAMP_FREQ) |
                        BIT(IIO_CHAN_INFO_PROCESSED),
        },
        {
                .type = IIO_PRESSURE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) |
                        BIT(IIO_CHAN_INFO_SAMP_FREQ) |
                        BIT(IIO_CHAN_INFO_PROCESSED),
        },
};

/* To be called after checking the COEF_RDY bit in MEAS_CFG */
static int dps310_get_coefs(struct dps310_data *data)
{
        int rc;
        u8 coef[18];
        u32 c0, c1;
        u32 c00, c10, c20, c30, c01, c11, c21;

        /* Read all sensor calibration coefficients from the COEF registers. */
        rc = regmap_bulk_read(data->regmap, DPS310_COEF_BASE, coef,
                              sizeof(coef));
        if (rc < 0)
                return rc;

        /*
         * Calculate temperature calibration coefficients c0 and c1. The
         * numbers are 12-bit 2's complement numbers.
         */
        c0 = (coef[0] << 4) | (coef[1] >> 4);
        data->c0 = sign_extend32(c0, 11);

        c1 = ((coef[1] & GENMASK(3, 0)) << 8) | coef[2];
        data->c1 = sign_extend32(c1, 11);

        /*
         * Calculate pressure calibration coefficients. c00 and c10 are 20 bit
         * 2's complement numbers, while the rest are 16 bit 2's complement
         * numbers.
         */
        c00 = (coef[3] << 12) | (coef[4] << 4) | (coef[5] >> 4);
        data->c00 = sign_extend32(c00, 19);

        c10 = ((coef[5] & GENMASK(3, 0)) << 16) | (coef[6] << 8) | coef[7];
        data->c10 = sign_extend32(c10, 19);

        c01 = (coef[8] << 8) | coef[9];
        data->c01 = sign_extend32(c01, 15);

        c11 = (coef[10] << 8) | coef[11];
        data->c11 = sign_extend32(c11, 15);

        c20 = (coef[12] << 8) | coef[13];
        data->c20 = sign_extend32(c20, 15);

        c21 = (coef[14] << 8) | coef[15];
        data->c21 = sign_extend32(c21, 15);

        c30 = (coef[16] << 8) | coef[17];
        data->c30 = sign_extend32(c30, 15);

        return 0;
}

static int dps310_get_pres_precision(struct dps310_data *data)
{
        int rc;
        int val;

        rc = regmap_read(data->regmap, DPS310_PRS_CFG, &val);
        if (rc < 0)
                return rc;

        return BIT(val & GENMASK(2, 0));
}

static int dps310_get_temp_precision(struct dps310_data *data)
{
        int rc;
        int val;

        rc = regmap_read(data->regmap, DPS310_TMP_CFG, &val);
        if (rc < 0)
                return rc;

        /*
         * Scale factor is bottom 4 bits of the register, but 1111 is
         * reserved so just grab bottom three
         */
        return BIT(val & GENMASK(2, 0));
}

/* Called with lock held */
static int dps310_set_pres_precision(struct dps310_data *data, int val)
{
        int rc;
        u8 shift_en;

        if (val < 0 || val > 128)
                return -EINVAL;

        shift_en = val >= 16 ? DPS310_PRS_SHIFT_EN : 0;
        rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
                               DPS310_PRS_SHIFT_EN, shift_en);
        if (rc)
                return rc;

        return regmap_update_bits(data->regmap, DPS310_PRS_CFG,
                                  DPS310_PRS_PRC_BITS, ilog2(val));
}

/* Called with lock held */
static int dps310_set_temp_precision(struct dps310_data *data, int val)
{
        int rc;
        u8 shift_en;

        if (val < 0 || val > 128)
                return -EINVAL;

        shift_en = val >= 16 ? DPS310_TMP_SHIFT_EN : 0;
        rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
                               DPS310_TMP_SHIFT_EN, shift_en);
        if (rc)
                return rc;

        return regmap_update_bits(data->regmap, DPS310_TMP_CFG,
                                  DPS310_TMP_PRC_BITS, ilog2(val));
}

/* Called with lock held */
static int dps310_set_pres_samp_freq(struct dps310_data *data, int freq)
{
        u8 val;

        if (freq < 0 || freq > 128)
                return -EINVAL;

        val = ilog2(freq) << 4;

        return regmap_update_bits(data->regmap, DPS310_PRS_CFG,
                                  DPS310_PRS_RATE_BITS, val);
}

/* Called with lock held */
static int dps310_set_temp_samp_freq(struct dps310_data *data, int freq)
{
        u8 val;

        if (freq < 0 || freq > 128)
                return -EINVAL;

        val = ilog2(freq) << 4;

        return regmap_update_bits(data->regmap, DPS310_TMP_CFG,
                                  DPS310_TMP_RATE_BITS, val);
}

static int dps310_get_pres_samp_freq(struct dps310_data *data)
{
        int rc;
        int val;

        rc = regmap_read(data->regmap, DPS310_PRS_CFG, &val);
        if (rc < 0)
                return rc;

        return BIT((val & DPS310_PRS_RATE_BITS) >> 4);
}

static int dps310_get_temp_samp_freq(struct dps310_data *data)
{
        int rc;
        int val;

        rc = regmap_read(data->regmap, DPS310_TMP_CFG, &val);
        if (rc < 0)
                return rc;

        return BIT((val & DPS310_TMP_RATE_BITS) >> 4);
}

static int dps310_get_pres_k(struct dps310_data *data)
{
        int rc = dps310_get_pres_precision(data);

        if (rc < 0)
                return rc;

        return scale_factors[ilog2(rc)];
}

static int dps310_get_temp_k(struct dps310_data *data)
{
        int rc = dps310_get_temp_precision(data);

        if (rc < 0)
                return rc;

        return scale_factors[ilog2(rc)];
}

static int dps310_read_pres_raw(struct dps310_data *data)
{
        int rc;
        int rate;
        int ready;
        int timeout;
        s32 raw;
        u8 val[3];

        if (mutex_lock_interruptible(&data->lock))
                return -EINTR;

        rate = dps310_get_pres_samp_freq(data);
        timeout = DPS310_POLL_TIMEOUT_US(rate);

        /* Poll for sensor readiness; base the timeout upon the sample rate. */
        rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
                                      ready & DPS310_PRS_RDY,
                                      DPS310_POLL_SLEEP_US(timeout), timeout);
        if (rc)
                goto done;

        rc = regmap_bulk_read(data->regmap, DPS310_PRS_BASE, val, sizeof(val));
        if (rc < 0)
                goto done;

        raw = (val[0] << 16) | (val[1] << 8) | val[2];
        data->pressure_raw = sign_extend32(raw, 23);

done:
        mutex_unlock(&data->lock);
        return rc;
}

/* Called with lock held */
static int dps310_read_temp_ready(struct dps310_data *data)
{
        int rc;
        u8 val[3];
        s32 raw;

        rc = regmap_bulk_read(data->regmap, DPS310_TMP_BASE, val, sizeof(val));
        if (rc < 0)
                return rc;

        raw = (val[0] << 16) | (val[1] << 8) | val[2];
        data->temp_raw = sign_extend32(raw, 23);

        return 0;
}

static int dps310_read_temp_raw(struct dps310_data *data)
{
        int rc;
        int rate;
        int ready;
        int timeout;

        if (mutex_lock_interruptible(&data->lock))
                return -EINTR;

        rate = dps310_get_temp_samp_freq(data);
        timeout = DPS310_POLL_TIMEOUT_US(rate);

        /* Poll for sensor readiness; base the timeout upon the sample rate. */
        rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
                                      ready & DPS310_TMP_RDY,
                                      DPS310_POLL_SLEEP_US(timeout), timeout);
        if (rc < 0)
                goto done;

        rc = dps310_read_temp_ready(data);

done:
        mutex_unlock(&data->lock);
        return rc;
}

static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case DPS310_PRS_CFG:
        case DPS310_TMP_CFG:
        case DPS310_MEAS_CFG:
        case DPS310_CFG_REG:
        case DPS310_RESET:
        /* No documentation available on the registers below */
        case 0x0e:
        case 0x0f:
        case 0x62:
                return true;
        default:
                return false;
        }
}

static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
{
        switch (reg) {
        case DPS310_PRS_B0:
        case DPS310_PRS_B1:
        case DPS310_PRS_B2:
        case DPS310_TMP_B0:
        case DPS310_TMP_B1:
        case DPS310_TMP_B2:
        case DPS310_MEAS_CFG:
        case 0x32:      /* No documentation available on this register */
                return true;
        default:
                return false;
        }
}

static int dps310_write_raw(struct iio_dev *iio,
                            struct iio_chan_spec const *chan, int val,
                            int val2, long mask)
{
        int rc;
        struct dps310_data *data = iio_priv(iio);

        if (mutex_lock_interruptible(&data->lock))
                return -EINTR;

        switch (mask) {
        case IIO_CHAN_INFO_SAMP_FREQ:
                switch (chan->type) {
                case IIO_PRESSURE:
                        rc = dps310_set_pres_samp_freq(data, val);
                        break;

                case IIO_TEMP:
                        rc = dps310_set_temp_samp_freq(data, val);
                        break;

                default:
                        rc = -EINVAL;
                        break;
                }
                break;

        case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
                switch (chan->type) {
                case IIO_PRESSURE:
                        rc = dps310_set_pres_precision(data, val);
                        break;

                case IIO_TEMP:
                        rc = dps310_set_temp_precision(data, val);
                        break;

                default:
                        rc = -EINVAL;
                        break;
                }
                break;

        default:
                rc = -EINVAL;
                break;
        }

        mutex_unlock(&data->lock);
        return rc;
}

static int dps310_calculate_pressure(struct dps310_data *data)
{
        int i;
        int rc;
        int t_ready;
        int kpi = dps310_get_pres_k(data);
        int kti = dps310_get_temp_k(data);
        s64 rem = 0ULL;
        s64 pressure = 0ULL;
        s64 p;
        s64 t;
        s64 denoms[7];
        s64 nums[7];
        s64 rems[7];
        s64 kp;
        s64 kt;

        if (kpi < 0)
                return kpi;

        if (kti < 0)
                return kti;

        kp = (s64)kpi;
        kt = (s64)kti;

        /* Refresh temp if it's ready, otherwise just use the latest value */
        if (mutex_trylock(&data->lock)) {
                rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &t_ready);
                if (rc >= 0 && t_ready & DPS310_TMP_RDY)
                        dps310_read_temp_ready(data);

                mutex_unlock(&data->lock);
        }

        p = (s64)data->pressure_raw;
        t = (s64)data->temp_raw;

        /* Section 4.9.1 of the DPS310 spec; algebra'd to avoid underflow */
        nums[0] = (s64)data->c00;
        denoms[0] = 1LL;
        nums[1] = p * (s64)data->c10;
        denoms[1] = kp;
        nums[2] = p * p * (s64)data->c20;
        denoms[2] = kp * kp;
        nums[3] = p * p * p * (s64)data->c30;
        denoms[3] = kp * kp * kp;
        nums[4] = t * (s64)data->c01;
        denoms[4] = kt;
        nums[5] = t * p * (s64)data->c11;
        denoms[5] = kp * kt;
        nums[6] = t * p * p * (s64)data->c21;
        denoms[6] = kp * kp * kt;

        /* Kernel lacks a div64_s64_rem function; denoms are all positive */
        for (i = 0; i < 7; ++i) {
                u64 irem;

                if (nums[i] < 0LL) {
                        pressure -= div64_u64_rem(-nums[i], denoms[i], &irem);
                        rems[i] = -irem;
                } else {
                        pressure += div64_u64_rem(nums[i], denoms[i], &irem);
                        rems[i] = (s64)irem;
                }
        }

        /* Increase precision and calculate the remainder sum */
        for (i = 0; i < 7; ++i)
                rem += div64_s64((s64)rems[i] * 1000000000LL, denoms[i]);

        pressure += div_s64(rem, 1000000000LL);
        if (pressure < 0LL)
                return -ERANGE;

        return (int)min_t(s64, pressure, INT_MAX);
}

static int dps310_read_pressure(struct dps310_data *data, int *val, int *val2,
                                long mask)
{
        int rc;

        switch (mask) {
        case IIO_CHAN_INFO_SAMP_FREQ:
                rc = dps310_get_pres_samp_freq(data);
                if (rc < 0)
                        return rc;

                *val = rc;
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_PROCESSED:
                rc = dps310_read_pres_raw(data);
                if (rc)
                        return rc;

                rc = dps310_calculate_pressure(data);
                if (rc < 0)
                        return rc;

                *val = rc;
                *val2 = 1000; /* Convert Pa to KPa per IIO ABI */
                return IIO_VAL_FRACTIONAL;

        case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
                rc = dps310_get_pres_precision(data);
                if (rc < 0)
                        return rc;

                *val = rc;
                return IIO_VAL_INT;

        default:
                return -EINVAL;
        }
}

static int dps310_calculate_temp(struct dps310_data *data)
{
        s64 c0;
        s64 t;
        int kt = dps310_get_temp_k(data);

        if (kt < 0)
                return kt;

        /* Obtain inverse-scaled offset */
        c0 = div_s64((s64)kt * (s64)data->c0, 2);

        /* Add the offset to the unscaled temperature */
        t = c0 + ((s64)data->temp_raw * (s64)data->c1);

        /* Convert to milliCelsius and scale the temperature */
        return (int)div_s64(t * 1000LL, kt);
}

static int dps310_read_temp(struct dps310_data *data, int *val, int *val2,
                            long mask)
{
        int rc;

        switch (mask) {
        case IIO_CHAN_INFO_SAMP_FREQ:
                rc = dps310_get_temp_samp_freq(data);
                if (rc < 0)
                        return rc;

                *val = rc;
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_PROCESSED:
                rc = dps310_read_temp_raw(data);
                if (rc)
                        return rc;

                rc = dps310_calculate_temp(data);
                if (rc < 0)
                        return rc;

                *val = rc;
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
                rc = dps310_get_temp_precision(data);
                if (rc < 0)
                        return rc;

                *val = rc;
                return IIO_VAL_INT;

        default:
                return -EINVAL;
        }
}

static int dps310_read_raw(struct iio_dev *iio,
                           struct iio_chan_spec const *chan,
                           int *val, int *val2, long mask)
{
        struct dps310_data *data = iio_priv(iio);

        switch (chan->type) {
        case IIO_PRESSURE:
                return dps310_read_pressure(data, val, val2, mask);

        case IIO_TEMP:
                return dps310_read_temp(data, val, val2, mask);

        default:
                return -EINVAL;
        }
}

static void dps310_reset(void *action_data)
{
        struct dps310_data *data = action_data;

        regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
}

static const struct regmap_config dps310_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .writeable_reg = dps310_is_writeable_reg,
        .volatile_reg = dps310_is_volatile_reg,
        .cache_type = REGCACHE_RBTREE,
        .max_register = 0x62, /* No documentation available on this register */
};

static const struct iio_info dps310_info = {
        .read_raw = dps310_read_raw,
        .write_raw = dps310_write_raw,
};

/*
 * Some verions of chip will read temperatures in the ~60C range when
 * its actually ~20C. This is the manufacturer recommended workaround
 * to correct the issue. The registers used below are undocumented.
 */
static int dps310_temp_workaround(struct dps310_data *data)
{
        int rc;
        int reg;

        rc = regmap_read(data->regmap, 0x32, &reg);
        if (rc < 0)
                return rc;

        /*
         * If bit 1 is set then the device is okay, and the workaround does not
         * need to be applied
         */
        if (reg & BIT(1))
                return 0;

        rc = regmap_write(data->regmap, 0x0e, 0xA5);
        if (rc < 0)
                return rc;

        rc = regmap_write(data->regmap, 0x0f, 0x96);
        if (rc < 0)
                return rc;

        rc = regmap_write(data->regmap, 0x62, 0x02);
        if (rc < 0)
                return rc;

        rc = regmap_write(data->regmap, 0x0e, 0x00);
        if (rc < 0)
                return rc;

        return regmap_write(data->regmap, 0x0f, 0x00);
}

static int dps310_probe(struct i2c_client *client,
                        const struct i2c_device_id *id)
{
        struct dps310_data *data;
        struct iio_dev *iio;
        int rc, ready;

        iio = devm_iio_device_alloc(&client->dev,  sizeof(*data));
        if (!iio)
                return -ENOMEM;

        data = iio_priv(iio);
        data->client = client;
        mutex_init(&data->lock);

        iio->name = id->name;
        iio->channels = dps310_channels;
        iio->num_channels = ARRAY_SIZE(dps310_channels);
        iio->info = &dps310_info;
        iio->modes = INDIO_DIRECT_MODE;

        data->regmap = devm_regmap_init_i2c(client, &dps310_regmap_config);
        if (IS_ERR(data->regmap))
                return PTR_ERR(data->regmap);

        /* Register to run the device reset when the device is removed */
        rc = devm_add_action_or_reset(&client->dev, dps310_reset, data);
        if (rc)
                return rc;

        /*
         * Set up pressure sensor in single sample, one measurement per second
         * mode
         */
        rc = regmap_write(data->regmap, DPS310_PRS_CFG, 0);

        /*
         * Set up external (MEMS) temperature sensor in single sample, one
         * measurement per second mode
         */
        rc = regmap_write(data->regmap, DPS310_TMP_CFG, DPS310_TMP_EXT);
        if (rc < 0)
                return rc;

        /* Temp and pressure shifts are disabled when PRC <= 8 */
        rc = regmap_write_bits(data->regmap, DPS310_CFG_REG,
                               DPS310_PRS_SHIFT_EN | DPS310_TMP_SHIFT_EN, 0);
        if (rc < 0)
                return rc;

        /* MEAS_CFG doesn't update correctly unless first written with 0 */
        rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
                               DPS310_MEAS_CTRL_BITS, 0);
        if (rc < 0)
                return rc;

        /* Turn on temperature and pressure measurement in the background */
        rc = regmap_write_bits(data->regmap, DPS310_MEAS_CFG,
                               DPS310_MEAS_CTRL_BITS, DPS310_PRS_EN |
                               DPS310_TEMP_EN | DPS310_BACKGROUND);
        if (rc < 0)
                return rc;

        /*
         * Calibration coefficients required for reporting temperature.
         * They are available 40ms after the device has started
         */
        rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
                                      ready & DPS310_COEF_RDY, 10000, 40000);
        if (rc < 0)
                return rc;

        rc = dps310_get_coefs(data);
        if (rc < 0)
                return rc;

        rc = dps310_temp_workaround(data);
        if (rc < 0)
                return rc;

        rc = devm_iio_device_register(&client->dev, iio);
        if (rc)
                return rc;

        i2c_set_clientdata(client, iio);

        return 0;
}

static const struct i2c_device_id dps310_id[] = {
        { DPS310_DEV_NAME, 0 },
        {}
};
MODULE_DEVICE_TABLE(i2c, dps310_id);

static struct i2c_driver dps310_driver = {
        .driver = {
                .name = DPS310_DEV_NAME,
        },
        .probe = dps310_probe,
        .id_table = dps310_id,
};
module_i2c_driver(dps310_driver);

MODULE_AUTHOR("Joel Stanley <joel@jms.id.au>");
MODULE_DESCRIPTION("Infineon DPS310 pressure and temperature sensor");
MODULE_LICENSE("GPL v2");