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                 /*
  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, &ltc4215_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, &ltc4215_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, &ltc4215_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");