2 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller
4 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; version 2 of the License.
11 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/init.h>
17 #include <linux/err.h>
18 #include <linux/slab.h>
19 #include <linux/i2c.h>
20 #include <linux/hwmon.h>
21 #include <linux/hwmon-sysfs.h>
23 /* Here are names of the chip's registers (a.k.a. commands) */
25 LTC4215_CONTROL = 0x00, /* rw */
26 LTC4215_ALERT = 0x01, /* rw */
27 LTC4215_STATUS = 0x02, /* ro */
28 LTC4215_FAULT = 0x03, /* rw */
29 LTC4215_SENSE = 0x04, /* rw */
30 LTC4215_SOURCE = 0x05, /* rw */
31 LTC4215_ADIN = 0x06, /* rw */
35 struct device *hwmon_dev;
37 struct mutex update_lock;
39 unsigned long last_updated; /* in jiffies */
45 static struct ltc4215_data *ltc4215_update_device(struct device *dev)
47 struct i2c_client *client = to_i2c_client(dev);
48 struct ltc4215_data *data = i2c_get_clientdata(client);
52 mutex_lock(&data->update_lock);
54 /* The chip's A/D updates 10 times per second */
55 if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
57 dev_dbg(&client->dev, "Starting ltc4215 update\n");
59 /* Read all registers */
60 for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
61 val = i2c_smbus_read_byte_data(client, i);
62 if (unlikely(val < 0))
68 data->last_updated = jiffies;
72 mutex_unlock(&data->update_lock);
77 /* Return the voltage from the given register in millivolts */
78 static int ltc4215_get_voltage(struct device *dev, u8 reg)
80 struct ltc4215_data *data = ltc4215_update_device(dev);
81 const u8 regval = data->regs[reg];
86 /* 151 uV per increment */
87 voltage = regval * 151 / 1000;
90 /* 60.5 mV per increment */
91 voltage = regval * 605 / 10;
95 * The ADIN input is divided by 12.5, and has 4.82 mV
96 * per increment, so we have the additional multiply
98 voltage = regval * 482 * 125 / 1000;
101 /* If we get here, the developer messed up */
109 /* Return the current from the sense resistor in mA */
110 static unsigned int ltc4215_get_current(struct device *dev)
112 struct ltc4215_data *data = ltc4215_update_device(dev);
115 * The strange looking conversions that follow are fixed-point
116 * math, since we cannot do floating point in the kernel.
118 * Step 1: convert sense register to microVolts
119 * Step 2: convert voltage to milliAmperes
121 * If you play around with the V=IR equation, you come up with
122 * the following: X uV / Y mOhm == Z mA
124 * With the resistors that are fractions of a milliOhm, we multiply
125 * the voltage and resistance by 10, to shift the decimal point.
126 * Now we can use the normal division operator again.
129 /* Calculate voltage in microVolts (151 uV per increment) */
130 const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
132 /* Calculate current in milliAmperes (4 milliOhm sense resistor) */
133 const unsigned int curr = voltage / 4;
138 static ssize_t ltc4215_show_voltage(struct device *dev,
139 struct device_attribute *da,
142 struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
143 const int voltage = ltc4215_get_voltage(dev, attr->index);
145 return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
148 static ssize_t ltc4215_show_current(struct device *dev,
149 struct device_attribute *da,
152 const unsigned int curr = ltc4215_get_current(dev);
154 return snprintf(buf, PAGE_SIZE, "%u\n", curr);
157 static ssize_t ltc4215_show_power(struct device *dev,
158 struct device_attribute *da,
161 const unsigned int curr = ltc4215_get_current(dev);
162 const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
164 /* current in mA * voltage in mV == power in uW */
165 const unsigned int power = abs(output_voltage * curr);
167 return snprintf(buf, PAGE_SIZE, "%u\n", power);
170 static ssize_t ltc4215_show_alarm(struct device *dev,
171 struct device_attribute *da,
174 struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
175 struct ltc4215_data *data = ltc4215_update_device(dev);
176 const u8 reg = data->regs[attr->index];
177 const u32 mask = attr->nr;
179 return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
183 * These macros are used below in constructing device attribute objects
184 * for use with sysfs_create_group() to make a sysfs device file
188 #define LTC4215_VOLTAGE(name, ltc4215_cmd_idx) \
189 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
190 ltc4215_show_voltage, NULL, ltc4215_cmd_idx)
192 #define LTC4215_CURRENT(name) \
193 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
194 ltc4215_show_current, NULL, 0);
196 #define LTC4215_POWER(name) \
197 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
198 ltc4215_show_power, NULL, 0);
200 #define LTC4215_ALARM(name, mask, reg) \
201 static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
202 ltc4215_show_alarm, NULL, (mask), reg)
204 /* Construct a sensor_device_attribute structure for each register */
207 LTC4215_CURRENT(curr1_input);
208 LTC4215_ALARM(curr1_max_alarm, (1 << 2), LTC4215_STATUS);
210 /* Power (virtual) */
211 LTC4215_POWER(power1_input);
214 LTC4215_VOLTAGE(in1_input, LTC4215_ADIN);
215 LTC4215_ALARM(in1_max_alarm, (1 << 0), LTC4215_STATUS);
216 LTC4215_ALARM(in1_min_alarm, (1 << 1), LTC4215_STATUS);
219 LTC4215_VOLTAGE(in2_input, LTC4215_SOURCE);
220 LTC4215_ALARM(in2_min_alarm, (1 << 3), LTC4215_STATUS);
223 * Finally, construct an array of pointers to members of the above objects,
224 * as required for sysfs_create_group()
226 static struct attribute *ltc4215_attributes[] = {
227 &sensor_dev_attr_curr1_input.dev_attr.attr,
228 &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
230 &sensor_dev_attr_power1_input.dev_attr.attr,
232 &sensor_dev_attr_in1_input.dev_attr.attr,
233 &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
234 &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
236 &sensor_dev_attr_in2_input.dev_attr.attr,
237 &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
242 static const struct attribute_group ltc4215_group = {
243 .attrs = ltc4215_attributes,
246 static int ltc4215_probe(struct i2c_client *client,
247 const struct i2c_device_id *id)
249 struct i2c_adapter *adapter = client->adapter;
250 struct ltc4215_data *data;
253 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
256 data = kzalloc(sizeof(*data), GFP_KERNEL);
262 i2c_set_clientdata(client, data);
263 mutex_init(&data->update_lock);
265 /* Initialize the LTC4215 chip */
266 i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
268 /* Register sysfs hooks */
269 ret = sysfs_create_group(&client->dev.kobj, <c4215_group);
271 goto out_sysfs_create_group;
273 data->hwmon_dev = hwmon_device_register(&client->dev);
274 if (IS_ERR(data->hwmon_dev)) {
275 ret = PTR_ERR(data->hwmon_dev);
276 goto out_hwmon_device_register;
281 out_hwmon_device_register:
282 sysfs_remove_group(&client->dev.kobj, <c4215_group);
283 out_sysfs_create_group:
289 static int ltc4215_remove(struct i2c_client *client)
291 struct ltc4215_data *data = i2c_get_clientdata(client);
293 hwmon_device_unregister(data->hwmon_dev);
294 sysfs_remove_group(&client->dev.kobj, <c4215_group);
301 static const struct i2c_device_id ltc4215_id[] = {
305 MODULE_DEVICE_TABLE(i2c, ltc4215_id);
307 /* This is the driver that will be inserted */
308 static struct i2c_driver ltc4215_driver = {
312 .probe = ltc4215_probe,
313 .remove = ltc4215_remove,
314 .id_table = ltc4215_id,
317 module_i2c_driver(ltc4215_driver);
319 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
320 MODULE_DESCRIPTION("LTC4215 driver");
321 MODULE_LICENSE("GPL");