1/*
2 * Driver for Linear Technology LTC4151 High Voltage I2C Current
3 * and Voltage Monitor
4 *
5 * Copyright (C) 2011 AppearTV AS
6 *
7 * Derived from:
8 *
9 *  Driver for Linear Technology LTC4261 I2C Negative Voltage Hot
10 *  Swap Controller
11 *  Copyright (C) 2010 Ericsson AB.
12 *
13 * Datasheet: http://www.linear.com/docs/Datasheet/4151fc.pdf
14 *
15 * This program is free software; you can redistribute it and/or modify
16 * it under the terms of the GNU General Public License as published by
17 * the Free Software Foundation; either version 2 of the License, or
18 * (at your option) any later version.
19 *
20 * This program is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
23 * GNU General Public License for more details.
24 *
25 * You should have received a copy of the GNU General Public License
26 * along with this program; if not, write to the Free Software
27 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
28 *
29 */
30
31#include <linux/kernel.h>
32#include <linux/module.h>
33#include <linux/init.h>
34#include <linux/err.h>
35#include <linux/slab.h>
36#include <linux/i2c.h>
37#include <linux/hwmon.h>
38#include <linux/hwmon-sysfs.h>
39#include <linux/jiffies.h>
40
41/* chip registers */
42#define LTC4151_SENSE_H	0x00
43#define LTC4151_SENSE_L	0x01
44#define LTC4151_VIN_H	0x02
45#define LTC4151_VIN_L	0x03
46#define LTC4151_ADIN_H	0x04
47#define LTC4151_ADIN_L	0x05
48
49struct ltc4151_data {
50	struct i2c_client *client;
51
52	struct mutex update_lock;
53	bool valid;
54	unsigned long last_updated; /* in jiffies */
55
56	/* Registers */
57	u8 regs[6];
58};
59
60static struct ltc4151_data *ltc4151_update_device(struct device *dev)
61{
62	struct ltc4151_data *data = dev_get_drvdata(dev);
63	struct i2c_client *client = data->client;
64	struct ltc4151_data *ret = data;
65
66	mutex_lock(&data->update_lock);
67
68	/*
69	 * The chip's A/D updates 6 times per second
70	 * (Conversion Rate 6 - 9 Hz)
71	 */
72	if (time_after(jiffies, data->last_updated + HZ / 6) || !data->valid) {
73		int i;
74
75		dev_dbg(&client->dev, "Starting ltc4151 update\n");
76
77		/* Read all registers */
78		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
79			int val;
80
81			val = i2c_smbus_read_byte_data(client, i);
82			if (unlikely(val < 0)) {
83				dev_dbg(dev,
84					"Failed to read ADC value: error %d\n",
85					val);
86				ret = ERR_PTR(val);
87				goto abort;
88			}
89			data->regs[i] = val;
90		}
91		data->last_updated = jiffies;
92		data->valid = 1;
93	}
94abort:
95	mutex_unlock(&data->update_lock);
96	return ret;
97}
98
99/* Return the voltage from the given register in mV */
100static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
101{
102	u32 val;
103
104	val = (data->regs[reg] << 4) + (data->regs[reg + 1] >> 4);
105
106	switch (reg) {
107	case LTC4151_ADIN_H:
108		/* 500uV resolution. Convert to mV. */
109		val = val * 500 / 1000;
110		break;
111	case LTC4151_SENSE_H:
112		/*
113		 * 20uV resolution. Convert to current as measured with
114		 * an 1 mOhm sense resistor, in mA.
115		 */
116		val = val * 20;
117		break;
118	case LTC4151_VIN_H:
119		/* 25 mV per increment */
120		val = val * 25;
121		break;
122	default:
123		/* If we get here, the developer messed up */
124		WARN_ON_ONCE(1);
125		val = 0;
126		break;
127	}
128
129	return val;
130}
131
132static ssize_t ltc4151_show_value(struct device *dev,
133				  struct device_attribute *da, char *buf)
134{
135	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
136	struct ltc4151_data *data = ltc4151_update_device(dev);
137	int value;
138
139	if (IS_ERR(data))
140		return PTR_ERR(data);
141
142	value = ltc4151_get_value(data, attr->index);
143	return snprintf(buf, PAGE_SIZE, "%d\n", value);
144}
145
146/*
147 * Input voltages.
148 */
149static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4151_show_value, NULL,
150			  LTC4151_VIN_H);
151static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4151_show_value, NULL,
152			  LTC4151_ADIN_H);
153
154/* Currents (via sense resistor) */
155static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4151_show_value, NULL,
156			  LTC4151_SENSE_H);
157
158/*
159 * Finally, construct an array of pointers to members of the above objects,
160 * as required for sysfs_create_group()
161 */
162static struct attribute *ltc4151_attrs[] = {
163	&sensor_dev_attr_in1_input.dev_attr.attr,
164	&sensor_dev_attr_in2_input.dev_attr.attr,
165
166	&sensor_dev_attr_curr1_input.dev_attr.attr,
167
168	NULL,
169};
170ATTRIBUTE_GROUPS(ltc4151);
171
172static int ltc4151_probe(struct i2c_client *client,
173			 const struct i2c_device_id *id)
174{
175	struct i2c_adapter *adapter = client->adapter;
176	struct device *dev = &client->dev;
177	struct ltc4151_data *data;
178	struct device *hwmon_dev;
179
180	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
181		return -ENODEV;
182
183	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
184	if (!data)
185		return -ENOMEM;
186
187	data->client = client;
188	mutex_init(&data->update_lock);
189
190	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
191							   data,
192							   ltc4151_groups);
193	return PTR_ERR_OR_ZERO(hwmon_dev);
194}
195
196static const struct i2c_device_id ltc4151_id[] = {
197	{ "ltc4151", 0 },
198	{ }
199};
200MODULE_DEVICE_TABLE(i2c, ltc4151_id);
201
202/* This is the driver that will be inserted */
203static struct i2c_driver ltc4151_driver = {
204	.driver = {
205		.name	= "ltc4151",
206	},
207	.probe		= ltc4151_probe,
208	.id_table	= ltc4151_id,
209};
210
211module_i2c_driver(ltc4151_driver);
212
213MODULE_AUTHOR("Per Dalen <per.dalen@appeartv.com>");
214MODULE_DESCRIPTION("LTC4151 driver");
215MODULE_LICENSE("GPL");
216