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
37 /* chip registers */
38 #define LTC4261_STATUS 0x00 /* readonly */
39 #define LTC4261_FAULT 0x01
40 #define LTC4261_ALERT 0x02
41 #define LTC4261_CONTROL 0x03
42 #define LTC4261_SENSE_H 0x04
43 #define LTC4261_SENSE_L 0x05
44 #define LTC4261_ADIN2_H 0x06
45 #define LTC4261_ADIN2_L 0x07
46 #define LTC4261_ADIN_H 0x08
47 #define LTC4261_ADIN_L 0x09
48
49 /*
50 * Fault register bits
51 */
52 #define FAULT_OV (1<<0)
53 #define FAULT_UV (1<<1)
54 #define FAULT_OC (1<<2)
55
56 struct ltc4261_data {
57 struct device *hwmon_dev;
58
59 struct mutex update_lock;
60 bool valid;
61 unsigned long last_updated; /* in jiffies */
62
63 /* Registers */
64 u8 regs[10];
65 };
66
ltc4261_update_device(struct device * dev)67 static struct ltc4261_data *ltc4261_update_device(struct device *dev)
68 {
69 struct i2c_client *client = to_i2c_client(dev);
70 struct ltc4261_data *data = i2c_get_clientdata(client);
71 struct ltc4261_data *ret = data;
72
73 mutex_lock(&data->update_lock);
74
75 if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
76 int i;
77
78 /* Read registers -- 0x00 to 0x09 */
79 for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
80 int val;
81
82 val = i2c_smbus_read_byte_data(client, i);
83 if (unlikely(val < 0)) {
84 dev_dbg(dev,
85 "Failed to read ADC value: error %d\n",
86 val);
87 ret = ERR_PTR(val);
88 goto abort;
89 }
90 data->regs[i] = val;
91 }
92 data->last_updated = jiffies;
93 data->valid = 1;
94 }
95 abort:
96 mutex_unlock(&data->update_lock);
97 return ret;
98 }
99
100 /* Return the voltage from the given register in mV or mA */
ltc4261_get_value(struct ltc4261_data * data,u8 reg)101 static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)
102 {
103 u32 val;
104
105 val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);
106
107 switch (reg) {
108 case LTC4261_ADIN_H:
109 case LTC4261_ADIN2_H:
110 /* 2.5mV resolution. Convert to mV. */
111 val = val * 25 / 10;
112 break;
113 case LTC4261_SENSE_H:
114 /*
115 * 62.5uV resolution. Convert to current as measured with
116 * an 1 mOhm sense resistor, in mA. If a different sense
117 * resistor is installed, calculate the actual current by
118 * dividing the reported current by the sense resistor value
119 * in mOhm.
120 */
121 val = val * 625 / 10;
122 break;
123 default:
124 /* If we get here, the developer messed up */
125 WARN_ON_ONCE(1);
126 val = 0;
127 break;
128 }
129
130 return val;
131 }
132
ltc4261_show_value(struct device * dev,struct device_attribute * da,char * buf)133 static ssize_t ltc4261_show_value(struct device *dev,
134 struct device_attribute *da, char *buf)
135 {
136 struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
137 struct ltc4261_data *data = ltc4261_update_device(dev);
138 int value;
139
140 if (IS_ERR(data))
141 return PTR_ERR(data);
142
143 value = ltc4261_get_value(data, attr->index);
144 return snprintf(buf, PAGE_SIZE, "%d\n", value);
145 }
146
ltc4261_show_bool(struct device * dev,struct device_attribute * da,char * buf)147 static ssize_t ltc4261_show_bool(struct device *dev,
148 struct device_attribute *da, char *buf)
149 {
150 struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
151 struct i2c_client *client = to_i2c_client(dev);
152 struct ltc4261_data *data = ltc4261_update_device(dev);
153 u8 fault;
154
155 if (IS_ERR(data))
156 return PTR_ERR(data);
157
158 fault = data->regs[LTC4261_FAULT] & attr->index;
159 if (fault) /* Clear reported faults in chip register */
160 i2c_smbus_write_byte_data(client, LTC4261_FAULT, ~fault);
161
162 return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);
163 }
164
165 /*
166 * These macros are used below in constructing device attribute objects
167 * for use with sysfs_create_group() to make a sysfs device file
168 * for each register.
169 */
170
171 #define LTC4261_VALUE(name, ltc4261_cmd_idx) \
172 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
173 ltc4261_show_value, NULL, ltc4261_cmd_idx)
174
175 #define LTC4261_BOOL(name, mask) \
176 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
177 ltc4261_show_bool, NULL, (mask))
178
179 /*
180 * Input voltages.
181 */
182 LTC4261_VALUE(in1_input, LTC4261_ADIN_H);
183 LTC4261_VALUE(in2_input, LTC4261_ADIN2_H);
184
185 /*
186 * Voltage alarms. The chip has only one set of voltage alarm status bits,
187 * triggered by input voltage alarms. In many designs, those alarms are
188 * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
189 * to the OV pin. ADIN2 is, however, not available on all chip variants.
190 * To ensure that the alarm condition is reported to the user, report it
191 * with both voltage sensors.
192 */
193 LTC4261_BOOL(in1_min_alarm, FAULT_UV);
194 LTC4261_BOOL(in1_max_alarm, FAULT_OV);
195 LTC4261_BOOL(in2_min_alarm, FAULT_UV);
196 LTC4261_BOOL(in2_max_alarm, FAULT_OV);
197
198 /* Currents (via sense resistor) */
199 LTC4261_VALUE(curr1_input, LTC4261_SENSE_H);
200
201 /* Overcurrent alarm */
202 LTC4261_BOOL(curr1_max_alarm, FAULT_OC);
203
204 static struct attribute *ltc4261_attributes[] = {
205 &sensor_dev_attr_in1_input.dev_attr.attr,
206 &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
207 &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
208 &sensor_dev_attr_in2_input.dev_attr.attr,
209 &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
210 &sensor_dev_attr_in2_max_alarm.dev_attr.attr,
211
212 &sensor_dev_attr_curr1_input.dev_attr.attr,
213 &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
214
215 NULL,
216 };
217
218 static const struct attribute_group ltc4261_group = {
219 .attrs = ltc4261_attributes,
220 };
221
ltc4261_probe(struct i2c_client * client,const struct i2c_device_id * id)222 static int ltc4261_probe(struct i2c_client *client,
223 const struct i2c_device_id *id)
224 {
225 struct i2c_adapter *adapter = client->adapter;
226 struct ltc4261_data *data;
227 int ret;
228
229 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
230 return -ENODEV;
231
232 if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {
233 dev_err(&client->dev, "Failed to read status register\n");
234 return -ENODEV;
235 }
236
237 data = kzalloc(sizeof(*data), GFP_KERNEL);
238 if (!data) {
239 ret = -ENOMEM;
240 goto out_kzalloc;
241 }
242
243 i2c_set_clientdata(client, data);
244 mutex_init(&data->update_lock);
245
246 /* Clear faults */
247 i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);
248
249 /* Register sysfs hooks */
250 ret = sysfs_create_group(&client->dev.kobj, <c4261_group);
251 if (ret)
252 goto out_sysfs_create_group;
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, <c4261_group);
264 out_sysfs_create_group:
265 kfree(data);
266 out_kzalloc:
267 return ret;
268 }
269
ltc4261_remove(struct i2c_client * client)270 static int ltc4261_remove(struct i2c_client *client)
271 {
272 struct ltc4261_data *data = i2c_get_clientdata(client);
273
274 hwmon_device_unregister(data->hwmon_dev);
275 sysfs_remove_group(&client->dev.kobj, <c4261_group);
276
277 kfree(data);
278
279 return 0;
280 }
281
282 static const struct i2c_device_id ltc4261_id[] = {
283 {"ltc4261", 0},
284 {}
285 };
286
287 MODULE_DEVICE_TABLE(i2c, ltc4261_id);
288
289 /* This is the driver that will be inserted */
290 static struct i2c_driver ltc4261_driver = {
291 .driver = {
292 .name = "ltc4261",
293 },
294 .probe = ltc4261_probe,
295 .remove = ltc4261_remove,
296 .id_table = ltc4261_id,
297 };
298
ltc4261_init(void)299 static int __init ltc4261_init(void)
300 {
301 return i2c_add_driver(<c4261_driver);
302 }
303
ltc4261_exit(void)304 static void __exit ltc4261_exit(void)
305 {
306 i2c_del_driver(<c4261_driver);
307 }
308
309 MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
310 MODULE_DESCRIPTION("LTC4261 driver");
311 MODULE_LICENSE("GPL");
312
313 module_init(ltc4261_init);
314 module_exit(ltc4261_exit);
315