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 /* 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                 /* The ADIN input is divided by 12.5, and has 4.82 mV
  95                  * per increment, so we have the additional multiply */
  96                 voltage = regval * 482 * 125 / 1000;
  97                 break;
  98         default:
  99                 /* If we get here, the developer messed up */
 100                 WARN_ON_ONCE(1);
 101                 break;
 102         }
 103
 104         return voltage;
 105 }
 106
 107 /* Return the current from the sense resistor in mA */
 108 static unsigned int ltc4215_get_current(struct device *dev)
 109 {
 110         struct ltc4215_data *data = ltc4215_update_device(dev);
 111
 112         /* The strange looking conversions that follow are fixed-point
 113          * math, since we cannot do floating point in the kernel.
 114          *
 115          * Step 1: convert sense register to microVolts
 116          * Step 2: convert voltage to milliAmperes
 117          *
 118          * If you play around with the V=IR equation, you come up with
 119          * the following: X uV / Y mOhm == Z mA
 120          *
 121          * With the resistors that are fractions of a milliOhm, we multiply
 122          * the voltage and resistance by 10, to shift the decimal point.
 123          * Now we can use the normal division operator again.
 124          */
 125
 126         /* Calculate voltage in microVolts (151 uV per increment) */
 127         const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
 128
 129         /* Calculate current in milliAmperes (4 milliOhm sense resistor) */
 130         const unsigned int curr = voltage / 4;
 131
 132         return curr;
 133 }
 134
 135 static ssize_t ltc4215_show_voltage(struct device *dev,
 136                                     struct device_attribute *da,
 137                                     char *buf)
 138 {
 139         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 140         const int voltage = ltc4215_get_voltage(dev, attr->index);
 141
 142         return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
 143 }
 144
 145 static ssize_t ltc4215_show_current(struct device *dev,
 146                                     struct device_attribute *da,
 147                                     char *buf)
 148 {
 149         const unsigned int curr = ltc4215_get_current(dev);
 150
 151         return snprintf(buf, PAGE_SIZE, "%u\n", curr);
 152 }
 153
 154 static ssize_t ltc4215_show_power(struct device *dev,
 155                                   struct device_attribute *da,
 156                                   char *buf)
 157 {
 158         const unsigned int curr = ltc4215_get_current(dev);
 159         const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
 160
 161         /* current in mA * voltage in mV == power in uW */
 162         const unsigned int power = abs(output_voltage * curr);
 163
 164         return snprintf(buf, PAGE_SIZE, "%u\n", power);
 165 }
 166
 167 static ssize_t ltc4215_show_alarm(struct device *dev,
 168                                           struct device_attribute *da,
 169                                           char *buf)
 170 {
 171         struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
 172         struct ltc4215_data *data = ltc4215_update_device(dev);
 173         const u8 reg = data->regs[attr->index];
 174         const u32 mask = attr->nr;
 175
 176         return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
 177 }
 178
 179 /* These macros are used below in constructing device attribute objects
 180  * for use with sysfs_create_group() to make a sysfs device file
 181  * for each register.
 182  */
 183
 184 #define LTC4215_VOLTAGE(name, ltc4215_cmd_idx) \
 185         static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 186         ltc4215_show_voltage, NULL, ltc4215_cmd_idx)
 187
 188 #define LTC4215_CURRENT(name) \
 189         static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 190         ltc4215_show_current, NULL, 0);
 191
 192 #define LTC4215_POWER(name) \
 193         static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 194         ltc4215_show_power, NULL, 0);
 195
 196 #define LTC4215_ALARM(name, mask, reg) \
 197         static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
 198         ltc4215_show_alarm, NULL, (mask), reg)
 199
 200 /* Construct a sensor_device_attribute structure for each register */
 201
 202 /* Current */
 203 LTC4215_CURRENT(curr1_input);
 204 LTC4215_ALARM(curr1_max_alarm,  (1 << 2),       LTC4215_STATUS);
 205
 206 /* Power (virtual) */
 207 LTC4215_POWER(power1_input);
 208 LTC4215_ALARM(power1_alarm,     (1 << 3),       LTC4215_STATUS);
 209
 210 /* Input Voltage */
 211 LTC4215_VOLTAGE(in1_input,                      LTC4215_ADIN);
 212 LTC4215_ALARM(in1_max_alarm,    (1 << 0),       LTC4215_STATUS);
 213 LTC4215_ALARM(in1_min_alarm,    (1 << 1),       LTC4215_STATUS);
 214
 215 /* Output Voltage */
 216 LTC4215_VOLTAGE(in2_input,                      LTC4215_SOURCE);
 217
 218 /* Finally, construct an array of pointers to members of the above objects,
 219  * as required for sysfs_create_group()
 220  */
 221 static struct attribute *ltc4215_attributes[] = {
 222         &sensor_dev_attr_curr1_input.dev_attr.attr,
 223         &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 224
 225         &sensor_dev_attr_power1_input.dev_attr.attr,
 226         &sensor_dev_attr_power1_alarm.dev_attr.attr,
 227
 228         &sensor_dev_attr_in1_input.dev_attr.attr,
 229         &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
 230         &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
 231
 232         &sensor_dev_attr_in2_input.dev_attr.attr,
 233
 234         NULL,
 235 };
 236
 237 static const struct attribute_group ltc4215_group = {
 238         .attrs = ltc4215_attributes,
 239 };
 240
 241 static int ltc4215_probe(struct i2c_client *client,
 242                          const struct i2c_device_id *id)
 243 {
 244         struct i2c_adapter *adapter = client->adapter;
 245         struct ltc4215_data *data;
 246         int ret;
 247
 248         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 249                 return -ENODEV;
 250
 251         data = kzalloc(sizeof(*data), GFP_KERNEL);
 252         if (!data) {
 253                 ret = -ENOMEM;
 254                 goto out_kzalloc;
 255         }
 256
 257         i2c_set_clientdata(client, data);
 258         mutex_init(&data->update_lock);
 259
 260         /* Initialize the LTC4215 chip */
 261         i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
 262
 263         /* Register sysfs hooks */
 264         ret = sysfs_create_group(&client->dev.kobj, &ltc4215_group);
 265         if (ret)
 266                 goto out_sysfs_create_group;
 267
 268         data->hwmon_dev = hwmon_device_register(&client->dev);
 269         if (IS_ERR(data->hwmon_dev)) {
 270                 ret = PTR_ERR(data->hwmon_dev);
 271                 goto out_hwmon_device_register;
 272         }
 273
 274         return 0;
 275
 276 out_hwmon_device_register:
 277         sysfs_remove_group(&client->dev.kobj, &ltc4215_group);
 278 out_sysfs_create_group:
 279         kfree(data);
 280 out_kzalloc:
 281         return ret;
 282 }
 283
 284 static int ltc4215_remove(struct i2c_client *client)
 285 {
 286         struct ltc4215_data *data = i2c_get_clientdata(client);
 287
 288         hwmon_device_unregister(data->hwmon_dev);
 289         sysfs_remove_group(&client->dev.kobj, &ltc4215_group);
 290
 291         kfree(data);
 292
 293         return 0;
 294 }
 295
 296 static const struct i2c_device_id ltc4215_id[] = {
 297         { "ltc4215", 0 },
 298         { }
 299 };
 300 MODULE_DEVICE_TABLE(i2c, ltc4215_id);
 301
 302 /* This is the driver that will be inserted */
 303 static struct i2c_driver ltc4215_driver = {
 304         .driver = {
 305                 .name   = "ltc4215",
 306         },
 307         .probe          = ltc4215_probe,
 308         .remove         = ltc4215_remove,
 309         .id_table       = ltc4215_id,
 310 };
 311
 312 static int __init ltc4215_init(void)
 313 {
 314         return i2c_add_driver(&ltc4215_driver);
 315 }
 316
 317 static void __exit ltc4215_exit(void)
 318 {
 319         i2c_del_driver(&ltc4215_driver);
 320 }
 321
 322 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 323 MODULE_DESCRIPTION("LTC4215 driver");
 324 MODULE_LICENSE("GPL");
 325
 326 module_init(ltc4215_init);
 327 module_exit(ltc4215_exit);