/* Texas Instruments TMP108 SMBus temperature sensor driver
 *
 * Copyright (C) 2016 John Muir <john@jmuir.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.
 */

#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/regmap.h>
#include <linux/slab.h>

#define	DRIVER_NAME "tmp108"

#define	TMP108_REG_TEMP		0x00
#define	TMP108_REG_CONF		0x01
#define	TMP108_REG_TLOW		0x02
#define	TMP108_REG_THIGH	0x03

#define TMP108_TEMP_MIN_MC	-50000 /* Minimum millicelcius. */
#define TMP108_TEMP_MAX_MC	127937 /* Maximum millicelcius. */

/* Configuration register bits.
 * Note: these bit definitions are byte swapped.
 */
#define TMP108_CONF_M0		0x0100 /* Sensor mode. */
#define TMP108_CONF_M1		0x0200
#define TMP108_CONF_TM		0x0400 /* Thermostat mode. */
#define TMP108_CONF_FL		0x0800 /* Watchdog flag - TLOW */
#define TMP108_CONF_FH		0x1000 /* Watchdog flag - THIGH */
#define TMP108_CONF_CR0		0x2000 /* Conversion rate. */
#define TMP108_CONF_CR1		0x4000
#define TMP108_CONF_ID		0x8000
#define TMP108_CONF_HYS0	0x0010 /* Hysteresis. */
#define TMP108_CONF_HYS1	0x0020
#define TMP108_CONF_POL		0x0080 /* Polarity of alert. */

/* Defaults set by the hardware upon reset. */
#define TMP108_CONF_DEFAULTS		(TMP108_CONF_CR0 | TMP108_CONF_TM |\
					 TMP108_CONF_HYS0 | TMP108_CONF_M1)
/* These bits are read-only. */
#define TMP108_CONF_READ_ONLY		(TMP108_CONF_FL | TMP108_CONF_FH |\
					 TMP108_CONF_ID)

#define TMP108_CONF_MODE_MASK		(TMP108_CONF_M0|TMP108_CONF_M1)
#define TMP108_MODE_SHUTDOWN		0x0000
#define TMP108_MODE_ONE_SHOT		TMP108_CONF_M0
#define TMP108_MODE_CONTINUOUS		TMP108_CONF_M1		/* Default */
					/* When M1 is set, M0 is ignored. */

#define TMP108_CONF_CONVRATE_MASK	(TMP108_CONF_CR0|TMP108_CONF_CR1)
#define TMP108_CONVRATE_0P25HZ		0x0000
#define TMP108_CONVRATE_1HZ		TMP108_CONF_CR0		/* Default */
#define TMP108_CONVRATE_4HZ		TMP108_CONF_CR1
#define TMP108_CONVRATE_16HZ		(TMP108_CONF_CR0|TMP108_CONF_CR1)

#define TMP108_CONF_HYSTERESIS_MASK	(TMP108_CONF_HYS0|TMP108_CONF_HYS1)
#define TMP108_HYSTERESIS_0C		0x0000
#define TMP108_HYSTERESIS_1C		TMP108_CONF_HYS0	/* Default */
#define TMP108_HYSTERESIS_2C		TMP108_CONF_HYS1
#define TMP108_HYSTERESIS_4C		(TMP108_CONF_HYS0|TMP108_CONF_HYS1)

#define TMP108_CONVERSION_TIME_MS	30	/* in milli-seconds */

struct tmp108 {
	struct regmap *regmap;
	u16 orig_config;
	unsigned long ready_time;
};

/* convert 12-bit TMP108 register value to milliCelsius */
static inline int tmp108_temp_reg_to_mC(s16 val)
{
	return (val & ~0x0f) * 1000 / 256;
}

/* convert milliCelsius to left adjusted 12-bit TMP108 register value */
static inline u16 tmp108_mC_to_temp_reg(int val)
{
	return (val * 256) / 1000;
}

static int tmp108_read(struct device *dev, enum hwmon_sensor_types type,
		       u32 attr, int channel, long *temp)
{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);
	unsigned int regval;
	int err, hyst;

	if (type == hwmon_chip) {
		if (attr == hwmon_chip_update_interval) {
			err = regmap_read(tmp108->regmap, TMP108_REG_CONF,
					  &regval);
			if (err < 0)
				return err;
			switch (regval & TMP108_CONF_CONVRATE_MASK) {
			case TMP108_CONVRATE_0P25HZ:
			default:
				*temp = 4000;
				break;
			case TMP108_CONVRATE_1HZ:
				*temp = 1000;
				break;
			case TMP108_CONVRATE_4HZ:
				*temp = 250;
				break;
			case TMP108_CONVRATE_16HZ:
				*temp = 63;
				break;
			}
			return 0;
		}
		return -EOPNOTSUPP;
	}

	switch (attr) {
	case hwmon_temp_input:
		/* Is it too early to return a conversion ? */
		if (time_before(jiffies, tmp108->ready_time)) {
			dev_dbg(dev, "%s: Conversion not ready yet..\n",
				__func__);
			return -EAGAIN;
		}
		err = regmap_read(tmp108->regmap, TMP108_REG_TEMP, &regval);
		if (err < 0)
			return err;
		*temp = tmp108_temp_reg_to_mC(regval);
		break;
	case hwmon_temp_min:
	case hwmon_temp_max:
		err = regmap_read(tmp108->regmap, attr == hwmon_temp_min ?
				  TMP108_REG_TLOW : TMP108_REG_THIGH, &regval);
		if (err < 0)
			return err;
		*temp = tmp108_temp_reg_to_mC(regval);
		break;
	case hwmon_temp_min_alarm:
	case hwmon_temp_max_alarm:
		err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &regval);
		if (err < 0)
			return err;
		*temp = !!(regval & (attr == hwmon_temp_min_alarm ?
				     TMP108_CONF_FL : TMP108_CONF_FH));
		break;
	case hwmon_temp_min_hyst:
	case hwmon_temp_max_hyst:
		err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &regval);
		if (err < 0)
			return err;
		switch (regval & TMP108_CONF_HYSTERESIS_MASK) {
		case TMP108_HYSTERESIS_0C:
		default:
			hyst = 0;
			break;
		case TMP108_HYSTERESIS_1C:
			hyst = 1000;
			break;
		case TMP108_HYSTERESIS_2C:
			hyst = 2000;
			break;
		case TMP108_HYSTERESIS_4C:
			hyst = 4000;
			break;
		}
		err = regmap_read(tmp108->regmap, attr == hwmon_temp_min_hyst ?
				  TMP108_REG_TLOW : TMP108_REG_THIGH, &regval);
		if (err < 0)
			return err;
		*temp = tmp108_temp_reg_to_mC(regval);
		if (attr == hwmon_temp_min_hyst)
			*temp += hyst;
		else
			*temp -= hyst;
		break;
	default:
		return -EOPNOTSUPP;
	}

	return 0;
}

static int tmp108_write(struct device *dev, enum hwmon_sensor_types type,
			u32 attr, int channel, long temp)
{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);
	u32 regval, mask;
	int err;

	if (type == hwmon_chip) {
		if (attr == hwmon_chip_update_interval) {
			if (temp < 156)
				mask = TMP108_CONVRATE_16HZ;
			else if (temp < 625)
				mask = TMP108_CONVRATE_4HZ;
			else if (temp < 2500)
				mask = TMP108_CONVRATE_1HZ;
			else
				mask = TMP108_CONVRATE_0P25HZ;
			return regmap_update_bits(tmp108->regmap,
						  TMP108_REG_CONF,
						  TMP108_CONF_CONVRATE_MASK,
						  mask);
		}
		return -EOPNOTSUPP;
	}

	switch (attr) {
	case hwmon_temp_min:
	case hwmon_temp_max:
		temp = clamp_val(temp, TMP108_TEMP_MIN_MC, TMP108_TEMP_MAX_MC);
		return regmap_write(tmp108->regmap,
				    attr == hwmon_temp_min ?
					TMP108_REG_TLOW : TMP108_REG_THIGH,
				    tmp108_mC_to_temp_reg(temp));
	case hwmon_temp_min_hyst:
	case hwmon_temp_max_hyst:
		temp = clamp_val(temp, TMP108_TEMP_MIN_MC, TMP108_TEMP_MAX_MC);
		err = regmap_read(tmp108->regmap,
				  attr == hwmon_temp_min_hyst ?
					TMP108_REG_TLOW : TMP108_REG_THIGH,
				  &regval);
		if (err < 0)
			return err;
		if (attr == hwmon_temp_min_hyst)
			temp -= tmp108_temp_reg_to_mC(regval);
		else
			temp = tmp108_temp_reg_to_mC(regval) - temp;
		if (temp < 500)
			mask = TMP108_HYSTERESIS_0C;
		else if (temp < 1500)
			mask = TMP108_HYSTERESIS_1C;
		else if (temp < 3000)
			mask = TMP108_HYSTERESIS_2C;
		else
			mask = TMP108_HYSTERESIS_4C;
		return regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
					  TMP108_CONF_HYSTERESIS_MASK, mask);
	default:
		return -EOPNOTSUPP;
	}
}

static umode_t tmp108_is_visible(const void *data, enum hwmon_sensor_types type,
				 u32 attr, int channel)
{
	if (type == hwmon_chip && attr == hwmon_chip_update_interval)
		return 0644;

	if (type != hwmon_temp)
		return 0;

	switch (attr) {
	case hwmon_temp_input:
	case hwmon_temp_min_alarm:
	case hwmon_temp_max_alarm:
		return 0444;
	case hwmon_temp_min:
	case hwmon_temp_max:
	case hwmon_temp_min_hyst:
	case hwmon_temp_max_hyst:
		return 0644;
	default:
		return 0;
	}
}

static u32 tmp108_chip_config[] = {
	HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL,
	0
};

static const struct hwmon_channel_info tmp108_chip = {
	.type = hwmon_chip,
	.config = tmp108_chip_config,
};

static u32 tmp108_temp_config[] = {
	HWMON_T_INPUT | HWMON_T_MAX | HWMON_T_MIN | HWMON_T_MIN_HYST
		| HWMON_T_MAX_HYST | HWMON_T_MIN_ALARM | HWMON_T_MAX_ALARM,
	0
};

static const struct hwmon_channel_info tmp108_temp = {
	.type = hwmon_temp,
	.config = tmp108_temp_config,
};

static const struct hwmon_channel_info *tmp108_info[] = {
	&tmp108_chip,
	&tmp108_temp,
	NULL
};

static const struct hwmon_ops tmp108_hwmon_ops = {
	.is_visible = tmp108_is_visible,
	.read = tmp108_read,
	.write = tmp108_write,
};

static const struct hwmon_chip_info tmp108_chip_info = {
	.ops = &tmp108_hwmon_ops,
	.info = tmp108_info,
};

static void tmp108_restore_config(void *data)
{
	struct tmp108 *tmp108 = data;

	regmap_write(tmp108->regmap, TMP108_REG_CONF, tmp108->orig_config);
}

static bool tmp108_is_writeable_reg(struct device *dev, unsigned int reg)
{
	return reg != TMP108_REG_TEMP;
}

static bool tmp108_is_volatile_reg(struct device *dev, unsigned int reg)
{
	/* Configuration register must be volatile to enable FL and FH. */
	return reg == TMP108_REG_TEMP || reg == TMP108_REG_CONF;
}

static const struct regmap_config tmp108_regmap_config = {
	.reg_bits = 8,
	.val_bits = 16,
	.max_register = TMP108_REG_THIGH,
	.writeable_reg = tmp108_is_writeable_reg,
	.volatile_reg = tmp108_is_volatile_reg,
	.val_format_endian = REGMAP_ENDIAN_BIG,
	.cache_type = REGCACHE_RBTREE,
	.use_single_rw = true,
};

static int tmp108_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct tmp108 *tmp108;
	int err;
	u32 config;

	if (!i2c_check_functionality(client->adapter,
				     I2C_FUNC_SMBUS_WORD_DATA)) {
		dev_err(dev,
			"adapter doesn't support SMBus word transactions\n");
		return -ENODEV;
	}

	tmp108 = devm_kzalloc(dev, sizeof(*tmp108), GFP_KERNEL);
	if (!tmp108)
		return -ENOMEM;

	dev_set_drvdata(dev, tmp108);

	tmp108->regmap = devm_regmap_init_i2c(client, &tmp108_regmap_config);
	if (IS_ERR(tmp108->regmap)) {
		err = PTR_ERR(tmp108->regmap);
		dev_err(dev, "regmap init failed: %d", err);
		return err;
	}

	err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &config);
	if (err < 0) {
		dev_err(dev, "error reading config register: %d", err);
		return err;
	}
	tmp108->orig_config = config;

	/* Only continuous mode is supported. */
	config &= ~TMP108_CONF_MODE_MASK;
	config |= TMP108_MODE_CONTINUOUS;

	/* Only comparator mode is supported. */
	config &= ~TMP108_CONF_TM;

	err = regmap_write(tmp108->regmap, TMP108_REG_CONF, config);
	if (err < 0) {
		dev_err(dev, "error writing config register: %d", err);
		return err;
	}

	tmp108->ready_time = jiffies;
	if ((tmp108->orig_config & TMP108_CONF_MODE_MASK) ==
	    TMP108_MODE_SHUTDOWN)
		tmp108->ready_time +=
			msecs_to_jiffies(TMP108_CONVERSION_TIME_MS);

	err = devm_add_action_or_reset(dev, tmp108_restore_config, tmp108);
	if (err) {
		dev_err(dev, "add action or reset failed: %d", err);
		return err;
	}

	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
							 tmp108,
							 &tmp108_chip_info,
							 NULL);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static int __maybe_unused tmp108_suspend(struct device *dev)
{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);

	return regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
				  TMP108_CONF_MODE_MASK, TMP108_MODE_SHUTDOWN);
}

static int __maybe_unused tmp108_resume(struct device *dev)
{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);
	int err;

	err = regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
				 TMP108_CONF_MODE_MASK, TMP108_MODE_CONTINUOUS);
	tmp108->ready_time = jiffies +
			     msecs_to_jiffies(TMP108_CONVERSION_TIME_MS);
	return err;
}

static SIMPLE_DEV_PM_OPS(tmp108_dev_pm_ops, tmp108_suspend, tmp108_resume);

static const struct i2c_device_id tmp108_i2c_ids[] = {
	{ "tmp108", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, tmp108_i2c_ids);

#ifdef CONFIG_OF
static const struct of_device_id tmp108_of_ids[] = {
	{ .compatible = "ti,tmp108", },
	{}
};
MODULE_DEVICE_TABLE(of, tmp108_of_ids);
#endif

static struct i2c_driver tmp108_driver = {
	.driver = {
		.name	= DRIVER_NAME,
		.pm	= &tmp108_dev_pm_ops,
		.of_match_table = of_match_ptr(tmp108_of_ids),
	},
	.probe		= tmp108_probe,
	.id_table	= tmp108_i2c_ids,
};

module_i2c_driver(tmp108_driver);

MODULE_AUTHOR("John Muir <john@jmuir.com>");
MODULE_DESCRIPTION("Texas Instruments TMP108 temperature sensor driver");
MODULE_LICENSE("GPL");
