/*
 * rfd77402.c - Support for RF Digital RFD77402 Time-of-Flight (distance) sensor
 *
 * Copyright 2017 Peter Meerwald-Stadler <pmeerw@pmeerw.net>
 *
 * 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.
 *
 * 7-bit I2C slave address 0x4c
 *
 * TODO: interrupt
 * https://media.digikey.com/pdf/Data%20Sheets/RF%20Digital%20PDFs/RFD77402.pdf
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/delay.h>

#include <linux/iio/iio.h>

#define RFD77402_DRV_NAME "rfd77402"

#define RFD77402_ICSR		0x00 /* Interrupt Control Status Register */
#define RFD77402_ICSR_INT_MODE	BIT(2)
#define RFD77402_ICSR_INT_POL	BIT(3)
#define RFD77402_ICSR_RESULT	BIT(4)
#define RFD77402_ICSR_M2H_MSG	BIT(5)
#define RFD77402_ICSR_H2M_MSG	BIT(6)
#define RFD77402_ICSR_RESET	BIT(7)

#define RFD77402_CMD_R		0x04
#define RFD77402_CMD_SINGLE	0x01
#define RFD77402_CMD_STANDBY	0x10
#define RFD77402_CMD_MCPU_OFF	0x11
#define RFD77402_CMD_MCPU_ON	0x12
#define RFD77402_CMD_RESET	BIT(6)
#define RFD77402_CMD_VALID	BIT(7)

#define RFD77402_STATUS_R	0x06
#define RFD77402_STATUS_PM_MASK	GENMASK(4, 0)
#define RFD77402_STATUS_STANDBY	0x00
#define RFD77402_STATUS_MCPU_OFF	0x10
#define RFD77402_STATUS_MCPU_ON	0x18

#define RFD77402_RESULT_R	0x08
#define RFD77402_RESULT_DIST_MASK	GENMASK(12, 2)
#define RFD77402_RESULT_ERR_MASK	GENMASK(14, 13)
#define RFD77402_RESULT_VALID	BIT(15)

#define RFD77402_PMU_CFG	0x14
#define RFD77402_PMU_MCPU_INIT	BIT(9)

#define RFD77402_I2C_INIT_CFG	0x1c
#define RFD77402_I2C_ADDR_INCR	BIT(0)
#define RFD77402_I2C_DATA_INCR	BIT(2)
#define RFD77402_I2C_HOST_DEBUG	BIT(5)
#define RFD77402_I2C_MCPU_DEBUG	BIT(6)

#define RFD77402_CMD_CFGR_A	0x0c
#define RFD77402_CMD_CFGR_B	0x0e
#define RFD77402_HFCFG_0	0x20
#define RFD77402_HFCFG_1	0x22
#define RFD77402_HFCFG_2	0x24
#define RFD77402_HFCFG_3	0x26

#define RFD77402_MOD_CHIP_ID	0x28

/* magic configuration values from datasheet */
static const struct {
	u8 reg;
	u16 val;
} rf77402_tof_config[] = {
	{RFD77402_CMD_CFGR_A,	0xe100},
	{RFD77402_CMD_CFGR_B,	0x10ff},
	{RFD77402_HFCFG_0,	0x07d0},
	{RFD77402_HFCFG_1,	0x5008},
	{RFD77402_HFCFG_2,	0xa041},
	{RFD77402_HFCFG_3,	0x45d4},
};

struct rfd77402_data {
	struct i2c_client *client;
	/* Serialize reads from the sensor */
	struct mutex lock;
};

static const struct iio_chan_spec rfd77402_channels[] = {
	{
		.type = IIO_DISTANCE,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
				      BIT(IIO_CHAN_INFO_SCALE),
	},
};

static int rfd77402_set_state(struct rfd77402_data *data, u8 state, u16 check)
{
	int ret;

	ret = i2c_smbus_write_byte_data(data->client, RFD77402_CMD_R,
					state | RFD77402_CMD_VALID);
	if (ret < 0)
		return ret;

	usleep_range(10000, 20000);

	ret = i2c_smbus_read_word_data(data->client, RFD77402_STATUS_R);
	if (ret < 0)
		return ret;
	if ((ret & RFD77402_STATUS_PM_MASK) != check)
		return -ENODEV;

	return 0;
}

static int rfd77402_measure(struct rfd77402_data *data)
{
	int ret;
	int tries = 10;

	ret = rfd77402_set_state(data, RFD77402_CMD_MCPU_ON,
				 RFD77402_STATUS_MCPU_ON);
	if (ret < 0)
		return ret;

	ret = i2c_smbus_write_byte_data(data->client, RFD77402_CMD_R,
					RFD77402_CMD_SINGLE |
					RFD77402_CMD_VALID);
	if (ret < 0)
		goto err;

	while (tries-- > 0) {
		ret = i2c_smbus_read_byte_data(data->client, RFD77402_ICSR);
		if (ret < 0)
			goto err;
		if (ret & RFD77402_ICSR_RESULT)
			break;
		msleep(20);
	}

	if (tries < 0) {
		ret = -ETIMEDOUT;
		goto err;
	}

	ret = i2c_smbus_read_word_data(data->client, RFD77402_RESULT_R);
	if (ret < 0)
		goto err;

	if ((ret & RFD77402_RESULT_ERR_MASK) ||
	    !(ret & RFD77402_RESULT_VALID)) {
		ret = -EIO;
		goto err;
	}

	return (ret & RFD77402_RESULT_DIST_MASK) >> 2;

err:
	rfd77402_set_state(data, RFD77402_CMD_MCPU_OFF,
			   RFD77402_STATUS_MCPU_OFF);
	return ret;
}

static int rfd77402_read_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan,
			     int *val, int *val2, long mask)
{
	struct rfd77402_data *data = iio_priv(indio_dev);
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		mutex_lock(&data->lock);
		ret = rfd77402_measure(data);
		mutex_unlock(&data->lock);
		if (ret < 0)
			return ret;
		*val = ret;
		return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
		/* 1 LSB is 1 mm */
		*val = 0;
		*val2 = 1000;
		return IIO_VAL_INT_PLUS_MICRO;
	default:
		return -EINVAL;
	}
}

static const struct iio_info rfd77402_info = {
	.read_raw = rfd77402_read_raw,
};

static int rfd77402_init(struct rfd77402_data *data)
{
	int ret, i;

	ret = rfd77402_set_state(data, RFD77402_CMD_STANDBY,
				 RFD77402_STATUS_STANDBY);
	if (ret < 0)
		return ret;

	/* configure INT pad as push-pull, active low */
	ret = i2c_smbus_write_byte_data(data->client, RFD77402_ICSR,
					RFD77402_ICSR_INT_MODE);
	if (ret < 0)
		return ret;

	/* I2C configuration */
	ret = i2c_smbus_write_word_data(data->client, RFD77402_I2C_INIT_CFG,
					RFD77402_I2C_ADDR_INCR |
					RFD77402_I2C_DATA_INCR |
					RFD77402_I2C_HOST_DEBUG	|
					RFD77402_I2C_MCPU_DEBUG);
	if (ret < 0)
		return ret;

	/* set initialization */
	ret = i2c_smbus_write_word_data(data->client, RFD77402_PMU_CFG, 0x0500);
	if (ret < 0)
		return ret;

	ret = rfd77402_set_state(data, RFD77402_CMD_MCPU_OFF,
				 RFD77402_STATUS_MCPU_OFF);
	if (ret < 0)
		return ret;

	/* set initialization */
	ret = i2c_smbus_write_word_data(data->client, RFD77402_PMU_CFG, 0x0600);
	if (ret < 0)
		return ret;

	ret = rfd77402_set_state(data, RFD77402_CMD_MCPU_ON,
				 RFD77402_STATUS_MCPU_ON);
	if (ret < 0)
		return ret;

	for (i = 0; i < ARRAY_SIZE(rf77402_tof_config); i++) {
		ret = i2c_smbus_write_word_data(data->client,
						rf77402_tof_config[i].reg,
						rf77402_tof_config[i].val);
		if (ret < 0)
			return ret;
	}

	ret = rfd77402_set_state(data, RFD77402_CMD_STANDBY,
				 RFD77402_STATUS_STANDBY);

	return ret;
}

static int rfd77402_powerdown(struct rfd77402_data *data)
{
	return rfd77402_set_state(data, RFD77402_CMD_STANDBY,
				  RFD77402_STATUS_STANDBY);
}

static int rfd77402_probe(struct i2c_client *client,
			  const struct i2c_device_id *id)
{
	struct rfd77402_data *data;
	struct iio_dev *indio_dev;
	int ret;

	ret = i2c_smbus_read_word_data(client, RFD77402_MOD_CHIP_ID);
	if (ret < 0)
		return ret;
	if (ret != 0xad01 && ret != 0xad02) /* known chip ids */
		return -ENODEV;

	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;
	mutex_init(&data->lock);

	indio_dev->dev.parent = &client->dev;
	indio_dev->info = &rfd77402_info;
	indio_dev->channels = rfd77402_channels;
	indio_dev->num_channels = ARRAY_SIZE(rfd77402_channels);
	indio_dev->name = RFD77402_DRV_NAME;
	indio_dev->modes = INDIO_DIRECT_MODE;

	ret = rfd77402_init(data);
	if (ret < 0)
		return ret;

	ret = iio_device_register(indio_dev);
	if (ret)
		goto err_powerdown;

	return 0;

err_powerdown:
	rfd77402_powerdown(data);
	return ret;
}

static int rfd77402_remove(struct i2c_client *client)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);

	iio_device_unregister(indio_dev);
	rfd77402_powerdown(iio_priv(indio_dev));

	return 0;
}

#ifdef CONFIG_PM_SLEEP
static int rfd77402_suspend(struct device *dev)
{
	struct rfd77402_data *data = iio_priv(i2c_get_clientdata(
				     to_i2c_client(dev)));

	return rfd77402_powerdown(data);
}

static int rfd77402_resume(struct device *dev)
{
	struct rfd77402_data *data = iio_priv(i2c_get_clientdata(
				     to_i2c_client(dev)));

	return rfd77402_init(data);
}
#endif

static SIMPLE_DEV_PM_OPS(rfd77402_pm_ops, rfd77402_suspend, rfd77402_resume);

static const struct i2c_device_id rfd77402_id[] = {
	{ "rfd77402", 0},
	{ }
};
MODULE_DEVICE_TABLE(i2c, rfd77402_id);

static struct i2c_driver rfd77402_driver = {
	.driver = {
		.name   = RFD77402_DRV_NAME,
		.pm     = &rfd77402_pm_ops,
	},
	.probe  = rfd77402_probe,
	.remove = rfd77402_remove,
	.id_table = rfd77402_id,
};

module_i2c_driver(rfd77402_driver);

MODULE_AUTHOR("Peter Meerwald-Stadler <pmeerw@pmeerw.net>");
MODULE_DESCRIPTION("RFD77402 Time-of-Flight sensor driver");
MODULE_LICENSE("GPL");