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ltc4261.c
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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 <[email protected]>
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 
57 struct ltc4261_data {
58  struct device *hwmon_dev;
59 
61  bool valid;
62  unsigned long last_updated; /* in jiffies */
63 
64  /* Registers */
65  u8 regs[10];
66 };
67 
68 static struct ltc4261_data *ltc4261_update_device(struct device *dev)
69 {
70  struct i2c_client *client = to_i2c_client(dev);
71  struct ltc4261_data *data = i2c_get_clientdata(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  }
97 abort:
98  mutex_unlock(&data->update_lock);
99  return ret;
100 }
101 
102 /* Return the voltage from the given register in mV or mA */
103 static 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 
135 static ssize_t ltc4261_show_value(struct device *dev,
136  struct device_attribute *da, char *buf)
137 {
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 
149 static 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 i2c_client *client = to_i2c_client(dev);
154  struct ltc4261_data *data = ltc4261_update_device(dev);
155  u8 fault;
156 
157  if (IS_ERR(data))
158  return PTR_ERR(data);
159 
160  fault = data->regs[LTC4261_FAULT] & attr->index;
161  if (fault) /* Clear reported faults in chip register */
162  i2c_smbus_write_byte_data(client, LTC4261_FAULT, ~fault);
163 
164  return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);
165 }
166 
167 /*
168  * These macros are used below in constructing device attribute objects
169  * for use with sysfs_create_group() to make a sysfs device file
170  * for each register.
171  */
172 
173 #define LTC4261_VALUE(name, ltc4261_cmd_idx) \
174  static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
175  ltc4261_show_value, NULL, ltc4261_cmd_idx)
176 
177 #define LTC4261_BOOL(name, mask) \
178  static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
179  ltc4261_show_bool, NULL, (mask))
180 
181 /*
182  * Input voltages.
183  */
184 LTC4261_VALUE(in1_input, LTC4261_ADIN_H);
185 LTC4261_VALUE(in2_input, LTC4261_ADIN2_H);
186 
187 /*
188  * Voltage alarms. The chip has only one set of voltage alarm status bits,
189  * triggered by input voltage alarms. In many designs, those alarms are
190  * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
191  * to the OV pin. ADIN2 is, however, not available on all chip variants.
192  * To ensure that the alarm condition is reported to the user, report it
193  * with both voltage sensors.
194  */
195 LTC4261_BOOL(in1_min_alarm, FAULT_UV);
196 LTC4261_BOOL(in1_max_alarm, FAULT_OV);
197 LTC4261_BOOL(in2_min_alarm, FAULT_UV);
198 LTC4261_BOOL(in2_max_alarm, FAULT_OV);
199 
200 /* Currents (via sense resistor) */
201 LTC4261_VALUE(curr1_input, LTC4261_SENSE_H);
202 
203 /* Overcurrent alarm */
204 LTC4261_BOOL(curr1_max_alarm, FAULT_OC);
205 
206 static struct attribute *ltc4261_attributes[] = {
207  &sensor_dev_attr_in1_input.dev_attr.attr,
208  &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
209  &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
210  &sensor_dev_attr_in2_input.dev_attr.attr,
211  &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
212  &sensor_dev_attr_in2_max_alarm.dev_attr.attr,
213 
214  &sensor_dev_attr_curr1_input.dev_attr.attr,
215  &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
216 
217  NULL,
218 };
219 
220 static const struct attribute_group ltc4261_group = {
221  .attrs = ltc4261_attributes,
222 };
223 
224 static int ltc4261_probe(struct i2c_client *client,
225  const struct i2c_device_id *id)
226 {
227  struct i2c_adapter *adapter = client->adapter;
228  struct ltc4261_data *data;
229  int ret;
230 
231  if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
232  return -ENODEV;
233 
234  if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {
235  dev_err(&client->dev, "Failed to read status register\n");
236  return -ENODEV;
237  }
238 
239  data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
240  if (!data)
241  return -ENOMEM;
242 
243  i2c_set_clientdata(client, data);
244  mutex_init(&data->update_lock);
245 
246  /* Clear faults */
248 
249  /* Register sysfs hooks */
250  ret = sysfs_create_group(&client->dev.kobj, &ltc4261_group);
251  if (ret)
252  return ret;
253 
254  data->hwmon_dev = hwmon_device_register(&client->dev);
255  if (IS_ERR(data->hwmon_dev)) {
256  ret = PTR_ERR(data->hwmon_dev);
257  goto out_hwmon_device_register;
258  }
259 
260  return 0;
261 
262 out_hwmon_device_register:
263  sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
264  return ret;
265 }
266 
267 static int ltc4261_remove(struct i2c_client *client)
268 {
269  struct ltc4261_data *data = i2c_get_clientdata(client);
270 
272  sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
273 
274  return 0;
275 }
276 
277 static const struct i2c_device_id ltc4261_id[] = {
278  {"ltc4261", 0},
279  {}
280 };
281 
282 MODULE_DEVICE_TABLE(i2c, ltc4261_id);
283 
284 /* This is the driver that will be inserted */
285 static struct i2c_driver ltc4261_driver = {
286  .driver = {
287  .name = "ltc4261",
288  },
289  .probe = ltc4261_probe,
290  .remove = ltc4261_remove,
291  .id_table = ltc4261_id,
292 };
293 
294 module_i2c_driver(ltc4261_driver);
295 
296 MODULE_AUTHOR("Guenter Roeck <[email protected]>");
297 MODULE_DESCRIPTION("LTC4261 driver");
298 MODULE_LICENSE("GPL");