1 /* 2 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller 3 * 4 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu> 5 * 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. 9 * 10 * Datasheet: 11 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697 12 */ 13 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> 22 23 /* Here are names of the chip's registers (a.k.a. commands) */ 24 enum ltc4215_cmd { 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 */ 32 }; 33 34 struct ltc4215_data { 35 struct device *hwmon_dev; 36 37 struct mutex update_lock; 38 bool valid; 39 unsigned long last_updated; /* in jiffies */ 40 41 /* Registers */ 42 u8 regs[7]; 43 }; 44 45 static struct ltc4215_data *ltc4215_update_device(struct device *dev) 46 { 47 struct i2c_client *client = to_i2c_client(dev); 48 struct ltc4215_data *data = i2c_get_clientdata(client); 49 s32 val; 50 int i; 51 52 mutex_lock(&data->update_lock); 53 54 /* The chip's A/D updates 10 times per second */ 55 if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) { 56 57 dev_dbg(&client->dev, "Starting ltc4215 update\n"); 58 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)) 63 data->regs[i] = 0; 64 else 65 data->regs[i] = val; 66 } 67 68 data->last_updated = jiffies; 69 data->valid = 1; 70 } 71 72 mutex_unlock(&data->update_lock); 73 74 return data; 75 } 76 77 /* Return the voltage from the given register in millivolts */ 78 static int ltc4215_get_voltage(struct device *dev, u8 reg) 79 { 80 struct ltc4215_data *data = ltc4215_update_device(dev); 81 const u8 regval = data->regs[reg]; 82 u32 voltage = 0; 83 84 switch (reg) { 85 case LTC4215_SENSE: 86 /* 151 uV per increment */ 87 voltage = regval * 151 / 1000; 88 break; 89 case LTC4215_SOURCE: 90 /* 60.5 mV per increment */ 91 voltage = regval * 605 / 10; 92 break; 93 case LTC4215_ADIN: 94 /* 95 * The ADIN input is divided by 12.5, and has 4.82 mV 96 * per increment, so we have the additional multiply 97 */ 98 voltage = regval * 482 * 125 / 1000; 99 break; 100 default: 101 /* If we get here, the developer messed up */ 102 WARN_ON_ONCE(1); 103 break; 104 } 105 106 return voltage; 107 } 108 109 /* Return the current from the sense resistor in mA */ 110 static unsigned int ltc4215_get_current(struct device *dev) 111 { 112 struct ltc4215_data *data = ltc4215_update_device(dev); 113 114 /* 115 * The strange looking conversions that follow are fixed-point 116 * math, since we cannot do floating point in the kernel. 117 * 118 * Step 1: convert sense register to microVolts 119 * Step 2: convert voltage to milliAmperes 120 * 121 * If you play around with the V=IR equation, you come up with 122 * the following: X uV / Y mOhm == Z mA 123 * 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. 127 */ 128 129 /* Calculate voltage in microVolts (151 uV per increment) */ 130 const unsigned int voltage = data->regs[LTC4215_SENSE] * 151; 131 132 /* Calculate current in milliAmperes (4 milliOhm sense resistor) */ 133 const unsigned int curr = voltage / 4; 134 135 return curr; 136 } 137 138 static ssize_t ltc4215_show_voltage(struct device *dev, 139 struct device_attribute *da, 140 char *buf) 141 { 142 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 143 const int voltage = ltc4215_get_voltage(dev, attr->index); 144 145 return snprintf(buf, PAGE_SIZE, "%d\n", voltage); 146 } 147 148 static ssize_t ltc4215_show_current(struct device *dev, 149 struct device_attribute *da, 150 char *buf) 151 { 152 const unsigned int curr = ltc4215_get_current(dev); 153 154 return snprintf(buf, PAGE_SIZE, "%u\n", curr); 155 } 156 157 static ssize_t ltc4215_show_power(struct device *dev, 158 struct device_attribute *da, 159 char *buf) 160 { 161 const unsigned int curr = ltc4215_get_current(dev); 162 const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN); 163 164 /* current in mA * voltage in mV == power in uW */ 165 const unsigned int power = abs(output_voltage * curr); 166 167 return snprintf(buf, PAGE_SIZE, "%u\n", power); 168 } 169 170 static ssize_t ltc4215_show_alarm(struct device *dev, 171 struct device_attribute *da, 172 char *buf) 173 { 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; 178 179 return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0); 180 } 181 182 /* 183 * These macros are used below in constructing device attribute objects 184 * for use with sysfs_create_group() to make a sysfs device file 185 * for each register. 186 */ 187 188 #define LTC4215_VOLTAGE(name, ltc4215_cmd_idx) \ 189 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \ 190 ltc4215_show_voltage, NULL, ltc4215_cmd_idx) 191 192 #define LTC4215_CURRENT(name) \ 193 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \ 194 ltc4215_show_current, NULL, 0); 195 196 #define LTC4215_POWER(name) \ 197 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \ 198 ltc4215_show_power, NULL, 0); 199 200 #define LTC4215_ALARM(name, mask, reg) \ 201 static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \ 202 ltc4215_show_alarm, NULL, (mask), reg) 203 204 /* Construct a sensor_device_attribute structure for each register */ 205 206 /* Current */ 207 LTC4215_CURRENT(curr1_input); 208 LTC4215_ALARM(curr1_max_alarm, (1 << 2), LTC4215_STATUS); 209 210 /* Power (virtual) */ 211 LTC4215_POWER(power1_input); 212 213 /* Input Voltage */ 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); 217 218 /* Output Voltage */ 219 LTC4215_VOLTAGE(in2_input, LTC4215_SOURCE); 220 LTC4215_ALARM(in2_min_alarm, (1 << 3), LTC4215_STATUS); 221 222 /* 223 * Finally, construct an array of pointers to members of the above objects, 224 * as required for sysfs_create_group() 225 */ 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, 229 230 &sensor_dev_attr_power1_input.dev_attr.attr, 231 232 &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, 235 236 &sensor_dev_attr_in2_input.dev_attr.attr, 237 &sensor_dev_attr_in2_min_alarm.dev_attr.attr, 238 239 NULL, 240 }; 241 242 static const struct attribute_group ltc4215_group = { 243 .attrs = ltc4215_attributes, 244 }; 245 246 static int ltc4215_probe(struct i2c_client *client, 247 const struct i2c_device_id *id) 248 { 249 struct i2c_adapter *adapter = client->adapter; 250 struct ltc4215_data *data; 251 int ret; 252 253 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) 254 return -ENODEV; 255 256 data = kzalloc(sizeof(*data), GFP_KERNEL); 257 if (!data) { 258 ret = -ENOMEM; 259 goto out_kzalloc; 260 } 261 262 i2c_set_clientdata(client, data); 263 mutex_init(&data->update_lock); 264 265 /* Initialize the LTC4215 chip */ 266 i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00); 267 268 /* Register sysfs hooks */ 269 ret = sysfs_create_group(&client->dev.kobj, <c4215_group); 270 if (ret) 271 goto out_sysfs_create_group; 272 273 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; 277 } 278 279 return 0; 280 281 out_hwmon_device_register: 282 sysfs_remove_group(&client->dev.kobj, <c4215_group); 283 out_sysfs_create_group: 284 kfree(data); 285 out_kzalloc: 286 return ret; 287 } 288 289 static int ltc4215_remove(struct i2c_client *client) 290 { 291 struct ltc4215_data *data = i2c_get_clientdata(client); 292 293 hwmon_device_unregister(data->hwmon_dev); 294 sysfs_remove_group(&client->dev.kobj, <c4215_group); 295 296 kfree(data); 297 298 return 0; 299 } 300 301 static const struct i2c_device_id ltc4215_id[] = { 302 { "ltc4215", 0 }, 303 { } 304 }; 305 MODULE_DEVICE_TABLE(i2c, ltc4215_id); 306 307 /* This is the driver that will be inserted */ 308 static struct i2c_driver ltc4215_driver = { 309 .driver = { 310 .name = "ltc4215", 311 }, 312 .probe = ltc4215_probe, 313 .remove = ltc4215_remove, 314 .id_table = ltc4215_id, 315 }; 316 317 module_i2c_driver(ltc4215_driver); 318 319 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>"); 320 MODULE_DESCRIPTION("LTC4215 driver"); 321 MODULE_LICENSE("GPL"); 322