drivers/power/ds2782_battery.c

   1 /*
   2  * I2C client/driver for the Maxim/Dallas DS2782 Stand-Alone Fuel Gauge IC
   3  *
   4  * Copyright (C) 2009 Bluewater Systems Ltd
   5  *
   6  * Author: Ryan Mallon <ryan@bluewatersys.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/types.h>
  17 #include <linux/errno.h>
  18 #include <linux/swab.h>
  19 #include <linux/i2c.h>
  20 #include <linux/idr.h>
  21 #include <linux/power_supply.h>
  22 #include <linux/slab.h>
  23
  24 #define DS2782_REG_RARC         0x06    /* Remaining active relative capacity */
  25
  26 #define DS2782_REG_VOLT_MSB     0x0c
  27 #define DS2782_REG_TEMP_MSB     0x0a
  28 #define DS2782_REG_CURRENT_MSB  0x0e
  29
  30 /* EEPROM Block */
  31 #define DS2782_REG_RSNSP        0x69    /* Sense resistor value */
  32
  33 /* Current unit measurement in uA for a 1 milli-ohm sense resistor */
  34 #define DS2782_CURRENT_UNITS    1563
  35
  36 #define to_ds2782_info(x) container_of(x, struct ds2782_info, battery)
  37
  38 struct ds2782_info {
  39         struct i2c_client       *client;
  40         struct power_supply     battery;
  41         int                     id;
  42 };
  43
  44 static DEFINE_IDR(battery_id);
  45 static DEFINE_MUTEX(battery_lock);
  46
  47 static inline int ds2782_read_reg(struct ds2782_info *info, int reg, u8 *val)
  48 {
  49         int ret;
  50
  51         ret = i2c_smbus_read_byte_data(info->client, reg);
  52         if (ret < 0) {
  53                 dev_err(&info->client->dev, "register read failed\n");
  54                 return ret;
  55         }
  56
  57         *val = ret;
  58         return 0;
  59 }
  60
  61 static inline int ds2782_read_reg16(struct ds2782_info *info, int reg_msb,
  62                                     s16 *val)
  63 {
  64         int ret;
  65
  66         ret = swab16(i2c_smbus_read_word_data(info->client, reg_msb));
  67         if (ret < 0) {
  68                 dev_err(&info->client->dev, "register read failed\n");
  69                 return ret;
  70         }
  71
  72         *val = ret;
  73         return 0;
  74 }
  75
  76 static int ds2782_get_temp(struct ds2782_info *info, int *temp)
  77 {
  78         s16 raw;
  79         int err;
  80
  81         /*
  82          * Temperature is measured in units of 0.125 degrees celcius, the
  83          * power_supply class measures temperature in tenths of degrees
  84          * celsius. The temperature value is stored as a 10 bit number, plus
  85          * sign in the upper bits of a 16 bit register.
  86          */
  87         err = ds2782_read_reg16(info, DS2782_REG_TEMP_MSB, &raw);
  88         if (err)
  89                 return err;
  90         *temp = ((raw / 32) * 125) / 100;
  91         return 0;
  92 }
  93
  94 static int ds2782_get_current(struct ds2782_info *info, int *current_uA)
  95 {
  96         int sense_res;
  97         int err;
  98         u8 sense_res_raw;
  99         s16 raw;
 100
 101         /*
 102          * The units of measurement for current are dependent on the value of
 103          * the sense resistor.
 104          */
 105         err = ds2782_read_reg(info, DS2782_REG_RSNSP, &sense_res_raw);
 106         if (err)
 107                 return err;
 108         if (sense_res_raw == 0) {
 109                 dev_err(&info->client->dev, "sense resistor value is 0\n");
 110                 return -ENXIO;
 111         }
 112         sense_res = 1000 / sense_res_raw;
 113
 114         dev_dbg(&info->client->dev, "sense resistor = %d milli-ohms\n",
 115                 sense_res);
 116         err = ds2782_read_reg16(info, DS2782_REG_CURRENT_MSB, &raw);
 117         if (err)
 118                 return err;
 119         *current_uA = raw * (DS2782_CURRENT_UNITS / sense_res);
 120         return 0;
 121 }
 122
 123 static int ds2782_get_voltage(struct ds2782_info *info, int *voltage_uA)
 124 {
 125         s16 raw;
 126         int err;
 127
 128         /*
 129          * Voltage is measured in units of 4.88mV. The voltage is stored as
 130          * a 10-bit number plus sign, in the upper bits of a 16-bit register
 131          */
 132         err = ds2782_read_reg16(info, DS2782_REG_VOLT_MSB, &raw);
 133         if (err)
 134                 return err;
 135         *voltage_uA = (raw / 32) * 4800;
 136         return 0;
 137 }
 138
 139 static int ds2782_get_capacity(struct ds2782_info *info, int *capacity)
 140 {
 141         int err;
 142         u8 raw;
 143
 144         err = ds2782_read_reg(info, DS2782_REG_RARC, &raw);
 145         if (err)
 146                 return err;
 147         *capacity = raw;
 148         return raw;
 149 }
 150
 151 static int ds2782_get_status(struct ds2782_info *info, int *status)
 152 {
 153         int err;
 154         int current_uA;
 155         int capacity;
 156
 157         err = ds2782_get_current(info, &current_uA);
 158         if (err)
 159                 return err;
 160
 161         err = ds2782_get_capacity(info, &capacity);
 162         if (err)
 163                 return err;
 164
 165         if (capacity == 100)
 166                 *status = POWER_SUPPLY_STATUS_FULL;
 167         else if (current_uA == 0)
 168                 *status = POWER_SUPPLY_STATUS_NOT_CHARGING;
 169         else if (current_uA < 0)
 170                 *status = POWER_SUPPLY_STATUS_DISCHARGING;
 171         else
 172                 *status = POWER_SUPPLY_STATUS_CHARGING;
 173
 174         return 0;
 175 }
 176
 177 static int ds2782_battery_get_property(struct power_supply *psy,
 178                                        enum power_supply_property prop,
 179                                        union power_supply_propval *val)
 180 {
 181         struct ds2782_info *info = to_ds2782_info(psy);
 182         int ret;
 183
 184         switch (prop) {
 185         case POWER_SUPPLY_PROP_STATUS:
 186                 ret = ds2782_get_status(info, &val->intval);
 187                 break;
 188
 189         case POWER_SUPPLY_PROP_CAPACITY:
 190                 ret = ds2782_get_capacity(info, &val->intval);
 191                 break;
 192
 193         case POWER_SUPPLY_PROP_VOLTAGE_NOW:
 194                 ret = ds2782_get_voltage(info, &val->intval);
 195                 break;
 196
 197         case POWER_SUPPLY_PROP_CURRENT_NOW:
 198                 ret = ds2782_get_current(info, &val->intval);
 199                 break;
 200
 201         case POWER_SUPPLY_PROP_TEMP:
 202                 ret = ds2782_get_temp(info, &val->intval);
 203                 break;
 204
 205         default:
 206                 ret = -EINVAL;
 207         }
 208
 209         return ret;
 210 }
 211
 212 static enum power_supply_property ds2782_battery_props[] = {
 213         POWER_SUPPLY_PROP_STATUS,
 214         POWER_SUPPLY_PROP_CAPACITY,
 215         POWER_SUPPLY_PROP_VOLTAGE_NOW,
 216         POWER_SUPPLY_PROP_CURRENT_NOW,
 217         POWER_SUPPLY_PROP_TEMP,
 218 };
 219
 220 static void ds2782_power_supply_init(struct power_supply *battery)
 221 {
 222         battery->type                   = POWER_SUPPLY_TYPE_BATTERY;
 223         battery->properties             = ds2782_battery_props;
 224         battery->num_properties         = ARRAY_SIZE(ds2782_battery_props);
 225         battery->get_property           = ds2782_battery_get_property;
 226         battery->external_power_changed = NULL;
 227 }
 228
 229 static int ds2782_battery_remove(struct i2c_client *client)
 230 {
 231         struct ds2782_info *info = i2c_get_clientdata(client);
 232
 233         power_supply_unregister(&info->battery);
 234         kfree(info->battery.name);
 235
 236         mutex_lock(&battery_lock);
 237         idr_remove(&battery_id, info->id);
 238         mutex_unlock(&battery_lock);
 239
 240         i2c_set_clientdata(client, info);
 241
 242         kfree(info);
 243         return 0;
 244 }
 245
 246 static int ds2782_battery_probe(struct i2c_client *client,
 247                                 const struct i2c_device_id *id)
 248 {
 249         struct ds2782_info *info;
 250         int ret;
 251         int num;
 252
 253         /* Get an ID for this battery */
 254         ret = idr_pre_get(&battery_id, GFP_KERNEL);
 255         if (ret == 0) {
 256                 ret = -ENOMEM;
 257                 goto fail_id;
 258         }
 259
 260         mutex_lock(&battery_lock);
 261         ret = idr_get_new(&battery_id, client, &num);
 262         mutex_unlock(&battery_lock);
 263         if (ret < 0)
 264                 goto fail_id;
 265
 266         info = kzalloc(sizeof(*info), GFP_KERNEL);
 267         if (!info) {
 268                 ret = -ENOMEM;
 269                 goto fail_info;
 270         }
 271
 272         info->battery.name = kasprintf(GFP_KERNEL, "ds2782-%d", num);
 273         if (!info->battery.name) {
 274                 ret = -ENOMEM;
 275                 goto fail_name;
 276         }
 277
 278         i2c_set_clientdata(client, info);
 279         info->client = client;
 280         ds2782_power_supply_init(&info->battery);
 281
 282         ret = power_supply_register(&client->dev, &info->battery);
 283         if (ret) {
 284                 dev_err(&client->dev, "failed to register battery\n");
 285                 goto fail_register;
 286         }
 287
 288         return 0;
 289
 290 fail_register:
 291         kfree(info->battery.name);
 292 fail_name:
 293         i2c_set_clientdata(client, info);
 294         kfree(info);
 295 fail_info:
 296         mutex_lock(&battery_lock);
 297         idr_remove(&battery_id, num);
 298         mutex_unlock(&battery_lock);
 299 fail_id:
 300         return ret;
 301 }
 302
 303 static const struct i2c_device_id ds2782_id[] = {
 304         {"ds2782", 0},
 305         {},
 306 };
 307
 308 static struct i2c_driver ds2782_battery_driver = {
 309         .driver         = {
 310                 .name   = "ds2782-battery",
 311         },
 312         .probe          = ds2782_battery_probe,
 313         .remove         = ds2782_battery_remove,
 314         .id_table       = ds2782_id,
 315 };
 316
 317 static int __init ds2782_init(void)
 318 {
 319         return i2c_add_driver(&ds2782_battery_driver);
 320 }
 321 module_init(ds2782_init);
 322
 323 static void __exit ds2782_exit(void)
 324 {
 325         i2c_del_driver(&ds2782_battery_driver);
 326 }
 327 module_exit(ds2782_exit);
 328
 329 MODULE_AUTHOR("Ryan Mallon <ryan@bluewatersys.com>");
 330 MODULE_DESCRIPTION("Maxim/Dallas DS2782 Stand-Alone Fuel Gauage IC driver");
 331 MODULE_LICENSE("GPL");