1/*
  2 * An hwmon driver for the Microchip TC74
  3 *
  4 * Copyright 2015 Maciej Szmigiero <mail@maciej.szmigiero.name>
  5 *
  6 * Based on ad7414.c:
  7 *	Copyright 2006 Stefan Roese, DENX Software Engineering
  8 *	Copyright 2008 Sean MacLennan, PIKA Technologies
  9 *	Copyright 2008 Frank Edelhaeuser, Spansion Inc.
 10 *
 11 * This program is free software; you can redistribute it and/or modify
 12 * it under the terms of the GNU General Public License as published by
 13 * the Free Software Foundation; either version 2 of the License, or
 14 * (at your option) any later version.
 15 */
 16
 17#include <linux/bitops.h>
 18#include <linux/err.h>
 19#include <linux/hwmon.h>
 20#include <linux/hwmon-sysfs.h>
 21#include <linux/i2c.h>
 22#include <linux/jiffies.h>
 23#include <linux/module.h>
 24#include <linux/mutex.h>
 25#include <linux/slab.h>
 26#include <linux/sysfs.h>
 27
 28/* TC74 registers */
 29#define TC74_REG_TEMP		0x00
 30#define TC74_REG_CONFIG		0x01
 31
 32struct tc74_data {
 33	struct i2c_client	*client;
 34	struct mutex		lock;	/* atomic read data updates */
 35	bool			valid;	/* validity of fields below */
 36	unsigned long		next_update;	/* In jiffies */
 37	s8			temp_input;	/* Temp value in dC */
 38};
 39
 40static int tc74_update_device(struct device *dev)
 41{
 42	struct tc74_data *data = dev_get_drvdata(dev);
 43	struct i2c_client *client = data->client;
 44	int ret;
 45
 46	ret = mutex_lock_interruptible(&data->lock);
 47	if (ret)
 48		return ret;
 49
 50	if (time_after(jiffies, data->next_update) || !data->valid) {
 51		s32 value;
 52
 53		value = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
 54		if (value < 0) {
 55			dev_dbg(&client->dev, "TC74_REG_CONFIG read err %d\n",
 56				(int)value);
 57
 58			ret = value;
 59			goto ret_unlock;
 60		}
 61
 62		if (!(value & BIT(6))) {
 63			/* not ready yet */
 64
 65			ret = -EAGAIN;
 66			goto ret_unlock;
 67		}
 68
 69		value = i2c_smbus_read_byte_data(client, TC74_REG_TEMP);
 70		if (value < 0) {
 71			dev_dbg(&client->dev, "TC74_REG_TEMP read err %d\n",
 72				(int)value);
 73
 74			ret = value;
 75			goto ret_unlock;
 76		}
 77
 78		data->temp_input = value;
 79		data->next_update = jiffies + HZ / 4;
 80		data->valid = true;
 81	}
 82
 83ret_unlock:
 84	mutex_unlock(&data->lock);
 85
 86	return ret;
 87}
 88
 89static ssize_t show_temp_input(struct device *dev,
 90			       struct device_attribute *attr, char *buf)
 91{
 92	struct tc74_data *data = dev_get_drvdata(dev);
 93	int ret;
 94
 95	ret = tc74_update_device(dev);
 96	if (ret)
 97		return ret;
 98
 99	return sprintf(buf, "%d\n", data->temp_input * 1000);
100}
101static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp_input, NULL, 0);
102
103static struct attribute *tc74_attrs[] = {
104	&sensor_dev_attr_temp1_input.dev_attr.attr,
105	NULL
106};
107
108ATTRIBUTE_GROUPS(tc74);
109
110static int tc74_probe(struct i2c_client *client,
111		      const struct i2c_device_id *dev_id)
112{
113	struct device *dev = &client->dev;
114	struct tc74_data *data;
115	struct device *hwmon_dev;
116	s32 conf;
117
118	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
119		return -EOPNOTSUPP;
120
121	data = devm_kzalloc(dev, sizeof(struct tc74_data), GFP_KERNEL);
122	if (!data)
123		return -ENOMEM;
124
125	data->client = client;
126	mutex_init(&data->lock);
127
128	/* Make sure the chip is powered up. */
129	conf = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
130	if (conf < 0) {
131		dev_err(dev, "unable to read config register\n");
132
133		return conf;
134	}
135
136	if (conf & 0x3f) {
137		dev_err(dev, "invalid config register value\n");
138
139		return -ENODEV;
140	}
141
142	if (conf & BIT(7)) {
143		s32 ret;
144
145		conf &= ~BIT(7);
146
147		ret = i2c_smbus_write_byte_data(client, TC74_REG_CONFIG, conf);
148		if (ret)
149			dev_warn(dev, "unable to disable STANDBY\n");
150	}
151
152	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
153							   client->name,
154							   data, tc74_groups);
155	return PTR_ERR_OR_ZERO(hwmon_dev);
156}
157
158static const struct i2c_device_id tc74_id[] = {
159	{ "tc74", 0 },
160	{}
161};
162MODULE_DEVICE_TABLE(i2c, tc74_id);
163
164static struct i2c_driver tc74_driver = {
165	.driver = {
166		.name	= "tc74",
167	},
168	.probe	= tc74_probe,
169	.id_table = tc74_id,
170};
171
172module_i2c_driver(tc74_driver);
173
174MODULE_AUTHOR("Maciej Szmigiero <mail@maciej.szmigiero.name>");
175
176MODULE_DESCRIPTION("TC74 driver");
177MODULE_LICENSE("GPL");