drivers/hwmon/ltc4215.c

   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, &ltc4215_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, &ltc4215_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, &ltc4215_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(&ltc4215_driver);
 352 }
 353
 354 static void __exit ltc4215_exit(void)
 355 {
 356         i2c_del_driver(&ltc4215_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);