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 static const unsigned short normal_i2c[] = { I2C_CLIENT_END }; 24 25 /* Insmod parameters */ 26 I2C_CLIENT_INSMOD_1(ltc4215); 27 28 /* Here are names of the chip's registers (a.k.a. commands) */ 29 enum ltc4215_cmd { 30 LTC4215_CONTROL = 0x00, /* rw */ 31 LTC4215_ALERT = 0x01, /* rw */ 32 LTC4215_STATUS = 0x02, /* ro */ 33 LTC4215_FAULT = 0x03, /* rw */ 34 LTC4215_SENSE = 0x04, /* rw */ 35 LTC4215_SOURCE = 0x05, /* rw */ 36 LTC4215_ADIN = 0x06, /* rw */ 37 }; 38 39 struct ltc4215_data { 40 struct device *hwmon_dev; 41 42 struct mutex update_lock; 43 bool valid; 44 unsigned long last_updated; /* in jiffies */ 45 46 /* Registers */ 47 u8 regs[7]; 48 }; 49 50 static struct ltc4215_data *ltc4215_update_device(struct device *dev) 51 { 52 struct i2c_client *client = to_i2c_client(dev); 53 struct ltc4215_data *data = i2c_get_clientdata(client); 54 s32 val; 55 int i; 56 57 mutex_lock(&data->update_lock); 58 59 /* The chip's A/D updates 10 times per second */ 60 if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) { 61 62 dev_dbg(&client->dev, "Starting ltc4215 update\n"); 63 64 /* Read all registers */ 65 for (i = 0; i < ARRAY_SIZE(data->regs); i++) { 66 val = i2c_smbus_read_byte_data(client, i); 67 if (unlikely(val < 0)) 68 data->regs[i] = 0; 69 else 70 data->regs[i] = val; 71 } 72 73 data->last_updated = jiffies; 74 data->valid = 1; 75 } 76 77 mutex_unlock(&data->update_lock); 78 79 return data; 80 } 81 82 /* Return the voltage from the given register in millivolts */ 83 static int ltc4215_get_voltage(struct device *dev, u8 reg) 84 { 85 struct ltc4215_data *data = ltc4215_update_device(dev); 86 const u8 regval = data->regs[reg]; 87 u32 voltage = 0; 88 89 switch (reg) { 90 case LTC4215_SENSE: 91 /* 151 uV per increment */ 92 voltage = regval * 151 / 1000; 93 break; 94 case LTC4215_SOURCE: 95 /* 60.5 mV per increment */ 96 voltage = regval * 605 / 10; 97 break; 98 case LTC4215_ADIN: 99 /* The ADIN input is divided by 12.5, and has 4.82 mV 100 * per increment, so we have the additional multiply */ 101 voltage = regval * 482 * 125 / 1000; 102 break; 103 default: 104 /* If we get here, the developer messed up */ 105 WARN_ON_ONCE(1); 106 break; 107 } 108 109 return voltage; 110 } 111 112 /* Return the current from the sense resistor in mA */ 113 static unsigned int ltc4215_get_current(struct device *dev) 114 { 115 struct ltc4215_data *data = ltc4215_update_device(dev); 116 117 /* The strange looking conversions that follow are fixed-point 118 * math, since we cannot do floating point in the kernel. 119 * 120 * Step 1: convert sense register to microVolts 121 * Step 2: convert voltage to milliAmperes 122 * 123 * If you play around with the V=IR equation, you come up with 124 * the following: X uV / Y mOhm == Z mA 125 * 126 * With the resistors that are fractions of a milliOhm, we multiply 127 * the voltage and resistance by 10, to shift the decimal point. 128 * Now we can use the normal division operator again. 129 */ 130 131 /* Calculate voltage in microVolts (151 uV per increment) */ 132 const unsigned int voltage = data->regs[LTC4215_SENSE] * 151; 133 134 /* Calculate current in milliAmperes (4 milliOhm sense resistor) */ 135 const unsigned int curr = voltage / 4; 136 137 return curr; 138 } 139 140 static ssize_t ltc4215_show_voltage(struct device *dev, 141 struct device_attribute *da, 142 char *buf) 143 { 144 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 145 const int voltage = ltc4215_get_voltage(dev, attr->index); 146 147 return snprintf(buf, PAGE_SIZE, "%d\n", voltage); 148 } 149 150 static ssize_t ltc4215_show_current(struct device *dev, 151 struct device_attribute *da, 152 char *buf) 153 { 154 const unsigned int curr = ltc4215_get_current(dev); 155 156 return snprintf(buf, PAGE_SIZE, "%u\n", curr); 157 } 158 159 static ssize_t ltc4215_show_power(struct device *dev, 160 struct device_attribute *da, 161 char *buf) 162 { 163 const unsigned int curr = ltc4215_get_current(dev); 164 const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN); 165 166 /* current in mA * voltage in mV == power in uW */ 167 const unsigned int power = abs(output_voltage * curr); 168 169 return snprintf(buf, PAGE_SIZE, "%u\n", power); 170 } 171 172 static ssize_t ltc4215_show_alarm(struct device *dev, 173 struct device_attribute *da, 174 char *buf) 175 { 176 struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da); 177 struct ltc4215_data *data = ltc4215_update_device(dev); 178 const u8 reg = data->regs[attr->index]; 179 const u32 mask = attr->nr; 180 181 return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0); 182 } 183 184 /* These macros are used below in constructing device attribute objects 185 * for use with sysfs_create_group() to make a sysfs device file 186 * for each register. 187 */ 188 189 #define LTC4215_VOLTAGE(name, ltc4215_cmd_idx) \ 190 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \ 191 ltc4215_show_voltage, NULL, ltc4215_cmd_idx) 192 193 #define LTC4215_CURRENT(name) \ 194 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \ 195 ltc4215_show_current, NULL, 0); 196 197 #define LTC4215_POWER(name) \ 198 static SENSOR_DEVICE_ATTR(name, S_IRUGO, \ 199 ltc4215_show_power, NULL, 0); 200 201 #define LTC4215_ALARM(name, mask, reg) \ 202 static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \ 203 ltc4215_show_alarm, NULL, (mask), reg) 204 205 /* Construct a sensor_device_attribute structure for each register */ 206 207 /* Current */ 208 LTC4215_CURRENT(curr1_input); 209 LTC4215_ALARM(curr1_max_alarm, (1 << 2), LTC4215_STATUS); 210 211 /* Power (virtual) */ 212 LTC4215_POWER(power1_input); 213 LTC4215_ALARM(power1_alarm, (1 << 3), LTC4215_STATUS); 214 215 /* Input Voltage */ 216 LTC4215_VOLTAGE(in1_input, LTC4215_ADIN); 217 LTC4215_ALARM(in1_max_alarm, (1 << 0), LTC4215_STATUS); 218 LTC4215_ALARM(in1_min_alarm, (1 << 1), LTC4215_STATUS); 219 220 /* Output Voltage */ 221 LTC4215_VOLTAGE(in2_input, LTC4215_SOURCE); 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 &sensor_dev_attr_power1_alarm.dev_attr.attr, 232 233 &sensor_dev_attr_in1_input.dev_attr.attr, 234 &sensor_dev_attr_in1_max_alarm.dev_attr.attr, 235 &sensor_dev_attr_in1_min_alarm.dev_attr.attr, 236 237 &sensor_dev_attr_in2_input.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 ltc4215_data *data; 250 int ret; 251 252 data = kzalloc(sizeof(*data), GFP_KERNEL); 253 if (!data) { 254 ret = -ENOMEM; 255 goto out_kzalloc; 256 } 257 258 i2c_set_clientdata(client, data); 259 mutex_init(&data->update_lock); 260 261 /* Initialize the LTC4215 chip */ 262 /* TODO */ 263 264 /* Register sysfs hooks */ 265 ret = sysfs_create_group(&client->dev.kobj, <c4215_group); 266 if (ret) 267 goto out_sysfs_create_group; 268 269 data->hwmon_dev = hwmon_device_register(&client->dev); 270 if (IS_ERR(data->hwmon_dev)) { 271 ret = PTR_ERR(data->hwmon_dev); 272 goto out_hwmon_device_register; 273 } 274 275 return 0; 276 277 out_hwmon_device_register: 278 sysfs_remove_group(&client->dev.kobj, <c4215_group); 279 out_sysfs_create_group: 280 kfree(data); 281 out_kzalloc: 282 return ret; 283 } 284 285 static int ltc4215_remove(struct i2c_client *client) 286 { 287 struct ltc4215_data *data = i2c_get_clientdata(client); 288 289 hwmon_device_unregister(data->hwmon_dev); 290 sysfs_remove_group(&client->dev.kobj, <c4215_group); 291 292 kfree(data); 293 294 return 0; 295 } 296 297 static int ltc4215_detect(struct i2c_client *client, 298 int kind, 299 struct i2c_board_info *info) 300 { 301 struct i2c_adapter *adapter = client->adapter; 302 303 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) 304 return -ENODEV; 305 306 if (kind < 0) { /* probed detection - check the chip type */ 307 s32 v; /* 8 bits from the chip, or -ERRNO */ 308 309 /* 310 * Register 0x01 bit b7 is reserved, expect 0 311 * Register 0x03 bit b6 and b7 are reserved, expect 0 312 */ 313 v = i2c_smbus_read_byte_data(client, LTC4215_ALERT); 314 if (v < 0 || (v & (1 << 7)) != 0) 315 return -ENODEV; 316 317 v = i2c_smbus_read_byte_data(client, LTC4215_FAULT); 318 if (v < 0 || (v & ((1 << 6) | (1 << 7))) != 0) 319 return -ENODEV; 320 } 321 322 strlcpy(info->type, "ltc4215", I2C_NAME_SIZE); 323 dev_info(&adapter->dev, "ltc4215 %s at address 0x%02x\n", 324 kind < 0 ? "probed" : "forced", 325 client->addr); 326 327 return 0; 328 } 329 330 static const struct i2c_device_id ltc4215_id[] = { 331 { "ltc4215", ltc4215 }, 332 { } 333 }; 334 MODULE_DEVICE_TABLE(i2c, ltc4215_id); 335 336 /* This is the driver that will be inserted */ 337 static struct i2c_driver ltc4215_driver = { 338 .class = I2C_CLASS_HWMON, 339 .driver = { 340 .name = "ltc4215", 341 }, 342 .probe = ltc4215_probe, 343 .remove = ltc4215_remove, 344 .id_table = ltc4215_id, 345 .detect = ltc4215_detect, 346 .address_data = &addr_data, 347 }; 348 349 static int __init ltc4215_init(void) 350 { 351 return i2c_add_driver(<c4215_driver); 352 } 353 354 static void __exit ltc4215_exit(void) 355 { 356 i2c_del_driver(<c4215_driver); 357 } 358 359 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>"); 360 MODULE_DESCRIPTION("LTC4215 driver"); 361 MODULE_LICENSE("GPL"); 362 363 module_init(ltc4215_init); 364 module_exit(ltc4215_exit); 365