1/*
2 * Driver for Linear Technology LTC4261 I2C Negative Voltage Hot Swap Controller
3 *
4 * Copyright (C) 2010 Ericsson AB.
5 *
6 * Derived from:
7 *
8 *  Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
9 *  Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
10 *
11 * Datasheet: http://cds.linear.com/docs/Datasheet/42612fb.pdf
12 *
13 * This program is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU General Public License as published by
15 * the Free Software Foundation; either version 2 of the License, or
16 * (at your option) any later version.
17 *
18 * This program is distributed in the hope that it will be useful,
19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
21 * GNU General Public License for more details.
22 *
23 * You should have received a copy of the GNU General Public License
24 * along with this program; if not, write to the Free Software
25 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
26 */
27
28#include <linux/kernel.h>
29#include <linux/module.h>
30#include <linux/init.h>
31#include <linux/err.h>
32#include <linux/slab.h>
33#include <linux/i2c.h>
34#include <linux/hwmon.h>
35#include <linux/hwmon-sysfs.h>
36#include <linux/jiffies.h>
37
38/* chip registers */
39#define LTC4261_STATUS	0x00	/* readonly */
40#define LTC4261_FAULT	0x01
41#define LTC4261_ALERT	0x02
42#define LTC4261_CONTROL	0x03
43#define LTC4261_SENSE_H	0x04
44#define LTC4261_SENSE_L	0x05
45#define LTC4261_ADIN2_H	0x06
46#define LTC4261_ADIN2_L	0x07
47#define LTC4261_ADIN_H	0x08
48#define LTC4261_ADIN_L	0x09
49
50/*
51 * Fault register bits
52 */
53#define FAULT_OV	(1<<0)
54#define FAULT_UV	(1<<1)
55#define FAULT_OC	(1<<2)
56
57struct ltc4261_data {
58	struct i2c_client *client;
59
60	struct mutex update_lock;
61	bool valid;
62	unsigned long last_updated;	/* in jiffies */
63
64	/* Registers */
65	u8 regs[10];
66};
67
68static struct ltc4261_data *ltc4261_update_device(struct device *dev)
69{
70	struct ltc4261_data *data = dev_get_drvdata(dev);
71	struct i2c_client *client = data->client;
72	struct ltc4261_data *ret = data;
73
74	mutex_lock(&data->update_lock);
75
76	if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
77		int i;
78
79		/* Read registers -- 0x00 to 0x09 */
80		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
81			int val;
82
83			val = i2c_smbus_read_byte_data(client, i);
84			if (unlikely(val < 0)) {
85				dev_dbg(dev,
86					"Failed to read ADC value: error %d\n",
87					val);
88				ret = ERR_PTR(val);
89				data->valid = 0;
90				goto abort;
91			}
92			data->regs[i] = val;
93		}
94		data->last_updated = jiffies;
95		data->valid = 1;
96	}
97abort:
98	mutex_unlock(&data->update_lock);
99	return ret;
100}
101
102/* Return the voltage from the given register in mV or mA */
103static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)
104{
105	u32 val;
106
107	val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);
108
109	switch (reg) {
110	case LTC4261_ADIN_H:
111	case LTC4261_ADIN2_H:
112		/* 2.5mV resolution. Convert to mV. */
113		val = val * 25 / 10;
114		break;
115	case LTC4261_SENSE_H:
116		/*
117		 * 62.5uV resolution. Convert to current as measured with
118		 * an 1 mOhm sense resistor, in mA. If a different sense
119		 * resistor is installed, calculate the actual current by
120		 * dividing the reported current by the sense resistor value
121		 * in mOhm.
122		 */
123		val = val * 625 / 10;
124		break;
125	default:
126		/* If we get here, the developer messed up */
127		WARN_ON_ONCE(1);
128		val = 0;
129		break;
130	}
131
132	return val;
133}
134
135static ssize_t ltc4261_show_value(struct device *dev,
136				  struct device_attribute *da, char *buf)
137{
138	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
139	struct ltc4261_data *data = ltc4261_update_device(dev);
140	int value;
141
142	if (IS_ERR(data))
143		return PTR_ERR(data);
144
145	value = ltc4261_get_value(data, attr->index);
146	return snprintf(buf, PAGE_SIZE, "%d\n", value);
147}
148
149static ssize_t ltc4261_show_bool(struct device *dev,
150				 struct device_attribute *da, char *buf)
151{
152	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
153	struct ltc4261_data *data = ltc4261_update_device(dev);
154	u8 fault;
155
156	if (IS_ERR(data))
157		return PTR_ERR(data);
158
159	fault = data->regs[LTC4261_FAULT] & attr->index;
160	if (fault)		/* Clear reported faults in chip register */
161		i2c_smbus_write_byte_data(data->client, LTC4261_FAULT, ~fault);
162
163	return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);
164}
165
166/*
167 * Input voltages.
168 */
169static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4261_show_value, NULL,
170			  LTC4261_ADIN_H);
171static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4261_show_value, NULL,
172			  LTC4261_ADIN2_H);
173
174/*
175 * Voltage alarms. The chip has only one set of voltage alarm status bits,
176 * triggered by input voltage alarms. In many designs, those alarms are
177 * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
178 * to the OV pin. ADIN2 is, however, not available on all chip variants.
179 * To ensure that the alarm condition is reported to the user, report it
180 * with both voltage sensors.
181 */
182static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4261_show_bool, NULL,
183			  FAULT_UV);
184static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4261_show_bool, NULL,
185			  FAULT_OV);
186static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4261_show_bool, NULL,
187			  FAULT_UV);
188static SENSOR_DEVICE_ATTR(in2_max_alarm, S_IRUGO, ltc4261_show_bool, NULL,
189			  FAULT_OV);
190
191/* Currents (via sense resistor) */
192static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4261_show_value, NULL,
193			  LTC4261_SENSE_H);
194
195/* Overcurrent alarm */
196static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4261_show_bool, NULL,
197			  FAULT_OC);
198
199static struct attribute *ltc4261_attrs[] = {
200	&sensor_dev_attr_in1_input.dev_attr.attr,
201	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
202	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
203	&sensor_dev_attr_in2_input.dev_attr.attr,
204	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
205	&sensor_dev_attr_in2_max_alarm.dev_attr.attr,
206
207	&sensor_dev_attr_curr1_input.dev_attr.attr,
208	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
209
210	NULL,
211};
212ATTRIBUTE_GROUPS(ltc4261);
213
214static int ltc4261_probe(struct i2c_client *client,
215			 const struct i2c_device_id *id)
216{
217	struct i2c_adapter *adapter = client->adapter;
218	struct device *dev = &client->dev;
219	struct ltc4261_data *data;
220	struct device *hwmon_dev;
221
222	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
223		return -ENODEV;
224
225	if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {
226		dev_err(dev, "Failed to read status register\n");
227		return -ENODEV;
228	}
229
230	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
231	if (!data)
232		return -ENOMEM;
233
234	data->client = client;
235	mutex_init(&data->update_lock);
236
237	/* Clear faults */
238	i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);
239
240	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
241							   data,
242							   ltc4261_groups);
243	return PTR_ERR_OR_ZERO(hwmon_dev);
244}
245
246static const struct i2c_device_id ltc4261_id[] = {
247	{"ltc4261", 0},
248	{}
249};
250
251MODULE_DEVICE_TABLE(i2c, ltc4261_id);
252
253/* This is the driver that will be inserted */
254static struct i2c_driver ltc4261_driver = {
255	.driver = {
256		   .name = "ltc4261",
257		   },
258	.probe = ltc4261_probe,
259	.id_table = ltc4261_id,
260};
261
262module_i2c_driver(ltc4261_driver);
263
264MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
265MODULE_DESCRIPTION("LTC4261 driver");
266MODULE_LICENSE("GPL");
267