/*
 * An hwmon driver for the Microchip TC74
 *
 * Copyright 2015 Maciej Szmigiero <mail@maciej.szmigiero.name>
 *
 * Based on ad7414.c:
 *	Copyright 2006 Stefan Roese, DENX Software Engineering
 *	Copyright 2008 Sean MacLennan, PIKA Technologies
 *	Copyright 2008 Frank Edelhaeuser, Spansion Inc.
 *
 * 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.
 */

#include <linux/bitops.h>
#include <linux/err.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

/* TC74 registers */
#define TC74_REG_TEMP		0x00
#define TC74_REG_CONFIG		0x01

struct tc74_data {
	struct i2c_client	*client;
	struct mutex		lock;	/* atomic read data updates */
	bool			valid;	/* validity of fields below */
	unsigned long		next_update;	/* In jiffies */
	s8			temp_input;	/* Temp value in dC */
};

static int tc74_update_device(struct device *dev)
{
	struct tc74_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	int ret;

	ret = mutex_lock_interruptible(&data->lock);
	if (ret)
		return ret;

	if (time_after(jiffies, data->next_update) || !data->valid) {
		s32 value;

		value = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
		if (value < 0) {
			dev_dbg(&client->dev, "TC74_REG_CONFIG read err %d\n",
				(int)value);

			ret = value;
			goto ret_unlock;
		}

		if (!(value & BIT(6))) {
			/* not ready yet */

			ret = -EAGAIN;
			goto ret_unlock;
		}

		value = i2c_smbus_read_byte_data(client, TC74_REG_TEMP);
		if (value < 0) {
			dev_dbg(&client->dev, "TC74_REG_TEMP read err %d\n",
				(int)value);

			ret = value;
			goto ret_unlock;
		}

		data->temp_input = value;
		data->next_update = jiffies + HZ / 4;
		data->valid = true;
	}

ret_unlock:
	mutex_unlock(&data->lock);

	return ret;
}

static ssize_t show_temp_input(struct device *dev,
			       struct device_attribute *attr, char *buf)
{
	struct tc74_data *data = dev_get_drvdata(dev);
	int ret;

	ret = tc74_update_device(dev);
	if (ret)
		return ret;

	return sprintf(buf, "%d\n", data->temp_input * 1000);
}
static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp_input, NULL, 0);

static struct attribute *tc74_attrs[] = {
	&sensor_dev_attr_temp1_input.dev_attr.attr,
	NULL
};

ATTRIBUTE_GROUPS(tc74);

static int tc74_probe(struct i2c_client *client,
		      const struct i2c_device_id *dev_id)
{
	struct device *dev = &client->dev;
	struct tc74_data *data;
	struct device *hwmon_dev;
	s32 conf;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
		return -EOPNOTSUPP;

	data = devm_kzalloc(dev, sizeof(struct tc74_data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

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

	/* Make sure the chip is powered up. */
	conf = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
	if (conf < 0) {
		dev_err(dev, "unable to read config register\n");

		return conf;
	}

	if (conf & 0x3f) {
		dev_err(dev, "invalid config register value\n");

		return -ENODEV;
	}

	if (conf & BIT(7)) {
		s32 ret;

		conf &= ~BIT(7);

		ret = i2c_smbus_write_byte_data(client, TC74_REG_CONFIG, conf);
		if (ret)
			dev_warn(dev, "unable to disable STANDBY\n");
	}

	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
							   client->name,
							   data, tc74_groups);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id tc74_id[] = {
	{ "tc74", 0 },
	{}
};
MODULE_DEVICE_TABLE(i2c, tc74_id);

static struct i2c_driver tc74_driver = {
	.driver = {
		.name	= "tc74",
	},
	.probe	= tc74_probe,
	.id_table = tc74_id,
};

module_i2c_driver(tc74_driver);

MODULE_AUTHOR("Maciej Szmigiero <mail@maciej.szmigiero.name>");

MODULE_DESCRIPTION("TC74 driver");
MODULE_LICENSE("GPL");