/*
 * pulsedlight-lidar-lite-v2.c - Support for PulsedLight LIDAR sensor
 *
 * Copyright (C) 2015 Matt Ranostay <mranostay@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * TODO: interrupt mode, and signal strength reporting
 */

#include <linux/err.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>

#define LIDAR_REG_CONTROL		0x00
#define LIDAR_REG_CONTROL_ACQUIRE	BIT(2)

#define LIDAR_REG_STATUS		0x01
#define LIDAR_REG_STATUS_INVALID	BIT(3)
#define LIDAR_REG_STATUS_READY		BIT(0)

#define LIDAR_REG_DATA_HBYTE		0x0f
#define LIDAR_REG_DATA_LBYTE		0x10
#define LIDAR_REG_DATA_WORD_READ	BIT(7)

#define LIDAR_REG_PWR_CONTROL	0x65

#define LIDAR_DRV_NAME "lidar"

struct lidar_data {
	struct iio_dev *indio_dev;
	struct i2c_client *client;

	int (*xfer)(struct lidar_data *data, u8 reg, u8 *val, int len);
	int i2c_enabled;

	u16 buffer[8]; /* 2 byte distance + 8 byte timestamp */
};

static const struct iio_chan_spec lidar_channels[] = {
	{
		.type = IIO_DISTANCE,
		.info_mask_separate =
			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
		.scan_index = 0,
		.scan_type = {
			.sign = 'u',
			.realbits = 16,
			.storagebits = 16,
		},
	},
	IIO_CHAN_SOFT_TIMESTAMP(1),
};

static int lidar_i2c_xfer(struct lidar_data *data, u8 reg, u8 *val, int len)
{
	struct i2c_client *client = data->client;
	struct i2c_msg msg[2];
	int ret;

	msg[0].addr = client->addr;
	msg[0].flags = client->flags | I2C_M_STOP;
	msg[0].len = 1;
	msg[0].buf  = (char *) &reg;

	msg[1].addr = client->addr;
	msg[1].flags = client->flags | I2C_M_RD;
	msg[1].len = len;
	msg[1].buf = (char *) val;

	ret = i2c_transfer(client->adapter, msg, 2);

	return (ret == 2) ? 0 : -EIO;
}

static int lidar_smbus_xfer(struct lidar_data *data, u8 reg, u8 *val, int len)
{
	struct i2c_client *client = data->client;
	int ret;

	/*
	 * Device needs a STOP condition between address write, and data read
	 * so in turn i2c_smbus_read_byte_data cannot be used
	 */

	while (len--) {
		ret = i2c_smbus_write_byte(client, reg++);
		if (ret < 0) {
			dev_err(&client->dev, "cannot write addr value");
			return ret;
		}

		ret = i2c_smbus_read_byte(client);
		if (ret < 0) {
			dev_err(&client->dev, "cannot read data value");
			return ret;
		}

		*(val++) = ret;
	}

	return 0;
}

static int lidar_read_byte(struct lidar_data *data, u8 reg)
{
	int ret;
	u8 val;

	ret = data->xfer(data, reg, &val, 1);
	if (ret < 0)
		return ret;

	return val;
}

static inline int lidar_write_control(struct lidar_data *data, int val)
{
	return i2c_smbus_write_byte_data(data->client, LIDAR_REG_CONTROL, val);
}

static inline int lidar_write_power(struct lidar_data *data, int val)
{
	return i2c_smbus_write_byte_data(data->client,
					 LIDAR_REG_PWR_CONTROL, val);
}

static int lidar_read_measurement(struct lidar_data *data, u16 *reg)
{
	int ret = data->xfer(data, LIDAR_REG_DATA_HBYTE |
			(data->i2c_enabled ? LIDAR_REG_DATA_WORD_READ : 0),
			(u8 *) reg, 2);

	if (!ret)
		*reg = be16_to_cpu(*reg);

	return ret;
}

static int lidar_get_measurement(struct lidar_data *data, u16 *reg)
{
	struct i2c_client *client = data->client;
	int tries = 10;
	int ret;

	pm_runtime_get_sync(&client->dev);

	/* start sample */
	ret = lidar_write_control(data, LIDAR_REG_CONTROL_ACQUIRE);
	if (ret < 0) {
		dev_err(&client->dev, "cannot send start measurement command");
		return ret;
	}

	while (tries--) {
		usleep_range(1000, 2000);

		ret = lidar_read_byte(data, LIDAR_REG_STATUS);
		if (ret < 0)
			break;

		/* return -EINVAL since laser is likely pointed out of range */
		if (ret & LIDAR_REG_STATUS_INVALID) {
			*reg = 0;
			ret = -EINVAL;
			break;
		}

		/* sample ready to read */
		if (!(ret & LIDAR_REG_STATUS_READY)) {
			ret = lidar_read_measurement(data, reg);
			break;
		}
		ret = -EIO;
	}
	pm_runtime_mark_last_busy(&client->dev);
	pm_runtime_put_autosuspend(&client->dev);

	return ret;
}

static int lidar_read_raw(struct iio_dev *indio_dev,
			  struct iio_chan_spec const *chan,
			  int *val, int *val2, long mask)
{
	struct lidar_data *data = iio_priv(indio_dev);
	int ret = -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_RAW: {
		u16 reg;

		if (iio_device_claim_direct_mode(indio_dev))
			return -EBUSY;

		ret = lidar_get_measurement(data, &reg);
		if (!ret) {
			*val = reg;
			ret = IIO_VAL_INT;
		}
		iio_device_release_direct_mode(indio_dev);
		break;
	}
	case IIO_CHAN_INFO_SCALE:
		*val = 0;
		*val2 = 10000;
		ret = IIO_VAL_INT_PLUS_MICRO;
		break;
	}

	return ret;
}

static irqreturn_t lidar_trigger_handler(int irq, void *private)
{
	struct iio_poll_func *pf = private;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct lidar_data *data = iio_priv(indio_dev);
	int ret;

	ret = lidar_get_measurement(data, data->buffer);
	if (!ret) {
		iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
						   iio_get_time_ns(indio_dev));
	} else if (ret != -EINVAL) {
		dev_err(&data->client->dev, "cannot read LIDAR measurement");
	}

	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
}

static const struct iio_info lidar_info = {
	.driver_module = THIS_MODULE,
	.read_raw = lidar_read_raw,
};

static int lidar_probe(struct i2c_client *client,
		       const struct i2c_device_id *id)
{
	struct lidar_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);

	if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
		data->xfer = lidar_i2c_xfer;
		data->i2c_enabled = 1;
	} else if (i2c_check_functionality(client->adapter,
				I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE))
		data->xfer = lidar_smbus_xfer;
	else
		return -EOPNOTSUPP;

	indio_dev->info = &lidar_info;
	indio_dev->name = LIDAR_DRV_NAME;
	indio_dev->channels = lidar_channels;
	indio_dev->num_channels = ARRAY_SIZE(lidar_channels);
	indio_dev->dev.parent = &client->dev;
	indio_dev->modes = INDIO_DIRECT_MODE;

	i2c_set_clientdata(client, indio_dev);

	data->client = client;
	data->indio_dev = indio_dev;

	ret = iio_triggered_buffer_setup(indio_dev, NULL,
					 lidar_trigger_handler, NULL);
	if (ret)
		return ret;

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

	pm_runtime_set_autosuspend_delay(&client->dev, 1000);
	pm_runtime_use_autosuspend(&client->dev);

	ret = pm_runtime_set_active(&client->dev);
	if (ret)
		goto error_unreg_buffer;
	pm_runtime_enable(&client->dev);
	pm_runtime_idle(&client->dev);

	return 0;

error_unreg_buffer:
	iio_triggered_buffer_cleanup(indio_dev);

	return ret;
}

static int lidar_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);

	pm_runtime_disable(&client->dev);
	pm_runtime_set_suspended(&client->dev);

	return 0;
}

static const struct i2c_device_id lidar_id[] = {
	{"lidar-lite-v2", 0},
	{"lidar-lite-v3", 0},
	{ },
};
MODULE_DEVICE_TABLE(i2c, lidar_id);

static const struct of_device_id lidar_dt_ids[] = {
	{ .compatible = "pulsedlight,lidar-lite-v2" },
	{ .compatible = "grmn,lidar-lite-v3" },
	{ }
};
MODULE_DEVICE_TABLE(of, lidar_dt_ids);

#ifdef CONFIG_PM
static int lidar_pm_runtime_suspend(struct device *dev)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
	struct lidar_data *data = iio_priv(indio_dev);

	return lidar_write_power(data, 0x0f);
}

static int lidar_pm_runtime_resume(struct device *dev)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
	struct lidar_data *data = iio_priv(indio_dev);
	int ret = lidar_write_power(data, 0);

	/* regulator and FPGA needs settling time */
	usleep_range(15000, 20000);

	return ret;
}
#endif

static const struct dev_pm_ops lidar_pm_ops = {
	SET_RUNTIME_PM_OPS(lidar_pm_runtime_suspend,
			   lidar_pm_runtime_resume, NULL)
};

static struct i2c_driver lidar_driver = {
	.driver = {
		.name	= LIDAR_DRV_NAME,
		.of_match_table	= of_match_ptr(lidar_dt_ids),
		.pm	= &lidar_pm_ops,
	},
	.probe		= lidar_probe,
	.remove		= lidar_remove,
	.id_table	= lidar_id,
};
module_i2c_driver(lidar_driver);

MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
MODULE_DESCRIPTION("PulsedLight LIDAR sensor");
MODULE_LICENSE("GPL");