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 #include <linux/jiffies.h>
  23
  24 /* Here are names of the chip's registers (a.k.a. commands) */
  25 enum ltc4215_cmd {
  26         LTC4215_CONTROL                 = 0x00, /* rw */
  27         LTC4215_ALERT                   = 0x01, /* rw */
  28         LTC4215_STATUS                  = 0x02, /* ro */
  29         LTC4215_FAULT                   = 0x03, /* rw */
  30         LTC4215_SENSE                   = 0x04, /* rw */
  31         LTC4215_SOURCE                  = 0x05, /* rw */
  32         LTC4215_ADIN                    = 0x06, /* rw */
  33 };
  34
  35 struct ltc4215_data {
  36         struct device *hwmon_dev;
  37
  38         struct mutex update_lock;
  39         bool valid;
  40         unsigned long last_updated; /* in jiffies */
  41
  42         /* Registers */
  43         u8 regs[7];
  44 };
  45
  46 static struct ltc4215_data *ltc4215_update_device(struct device *dev)
  47 {
  48         struct i2c_client *client = to_i2c_client(dev);
  49         struct ltc4215_data *data = i2c_get_clientdata(client);
  50         s32 val;
  51         int i;
  52
  53         mutex_lock(&data->update_lock);
  54
  55         /* The chip's A/D updates 10 times per second */
  56         if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
  57
  58                 dev_dbg(&client->dev, "Starting ltc4215 update\n");
  59
  60                 /* Read all registers */
  61                 for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
  62                         val = i2c_smbus_read_byte_data(client, i);
  63                         if (unlikely(val < 0))
  64                                 data->regs[i] = 0;
  65                         else
  66                                 data->regs[i] = val;
  67                 }
  68
  69                 data->last_updated = jiffies;
  70                 data->valid = 1;
  71         }
  72
  73         mutex_unlock(&data->update_lock);
  74
  75         return data;
  76 }
  77
  78 /* Return the voltage from the given register in millivolts */
  79 static int ltc4215_get_voltage(struct device *dev, u8 reg)
  80 {
  81         struct ltc4215_data *data = ltc4215_update_device(dev);
  82         const u8 regval = data->regs[reg];
  83         u32 voltage = 0;
  84
  85         switch (reg) {
  86         case LTC4215_SENSE:
  87                 /* 151 uV per increment */
  88                 voltage = regval * 151 / 1000;
  89                 break;
  90         case LTC4215_SOURCE:
  91                 /* 60.5 mV per increment */
  92                 voltage = regval * 605 / 10;
  93                 break;
  94         case LTC4215_ADIN:
  95                 /*
  96                  * The ADIN input is divided by 12.5, and has 4.82 mV
  97                  * per increment, so we have the additional multiply
  98                  */
  99                 voltage = regval * 482 * 125 / 1000;
 100                 break;
 101         default:
 102                 /* If we get here, the developer messed up */
 103                 WARN_ON_ONCE(1);
 104                 break;
 105         }
 106
 107         return voltage;
 108 }
 109
 110 /* Return the current from the sense resistor in mA */
 111 static unsigned int ltc4215_get_current(struct device *dev)
 112 {
 113         struct ltc4215_data *data = ltc4215_update_device(dev);
 114
 115         /*
 116          * The strange looking conversions that follow are fixed-point
 117          * math, since we cannot do floating point in the kernel.
 118          *
 119          * Step 1: convert sense register to microVolts
 120          * Step 2: convert voltage to milliAmperes
 121          *
 122          * If you play around with the V=IR equation, you come up with
 123          * the following: X uV / Y mOhm == Z mA
 124          *
 125          * With the resistors that are fractions of a milliOhm, we multiply
 126          * the voltage and resistance by 10, to shift the decimal point.
 127          * Now we can use the normal division operator again.
 128          */
 129
 130         /* Calculate voltage in microVolts (151 uV per increment) */
 131         const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
 132
 133         /* Calculate current in milliAmperes (4 milliOhm sense resistor) */
 134         const unsigned int curr = voltage / 4;
 135
 136         return curr;
 137 }
 138
 139 static ssize_t ltc4215_show_voltage(struct device *dev,
 140                                     struct device_attribute *da,
 141                                     char *buf)
 142 {
 143         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 144         const int voltage = ltc4215_get_voltage(dev, attr->index);
 145
 146         return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
 147 }
 148
 149 static ssize_t ltc4215_show_current(struct device *dev,
 150                                     struct device_attribute *da,
 151                                     char *buf)
 152 {
 153         const unsigned int curr = ltc4215_get_current(dev);
 154
 155         return snprintf(buf, PAGE_SIZE, "%u\n", curr);
 156 }
 157
 158 static ssize_t ltc4215_show_power(struct device *dev,
 159                                   struct device_attribute *da,
 160                                   char *buf)
 161 {
 162         const unsigned int curr = ltc4215_get_current(dev);
 163         const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
 164
 165         /* current in mA * voltage in mV == power in uW */
 166         const unsigned int power = abs(output_voltage * curr);
 167
 168         return snprintf(buf, PAGE_SIZE, "%u\n", power);
 169 }
 170
 171 static ssize_t ltc4215_show_alarm(struct device *dev,
 172                                           struct device_attribute *da,
 173                                           char *buf)
 174 {
 175         struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
 176         struct ltc4215_data *data = ltc4215_update_device(dev);
 177         const u8 reg = data->regs[attr->index];
 178         const u32 mask = attr->nr;
 179
 180         return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
 181 }
 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
 214 /* Input Voltage */
 215 LTC4215_VOLTAGE(in1_input,                      LTC4215_ADIN);
 216 LTC4215_ALARM(in1_max_alarm,    (1 << 0),       LTC4215_STATUS);
 217 LTC4215_ALARM(in1_min_alarm,    (1 << 1),       LTC4215_STATUS);
 218
 219 /* Output Voltage */
 220 LTC4215_VOLTAGE(in2_input,                      LTC4215_SOURCE);
 221 LTC4215_ALARM(in2_min_alarm,    (1 << 3),       LTC4215_STATUS);
 222
 223 /*
 224  * Finally, construct an array of pointers to members of the above objects,
 225  * as required for sysfs_create_group()
 226  */
 227 static struct attribute *ltc4215_attributes[] = {
 228         &sensor_dev_attr_curr1_input.dev_attr.attr,
 229         &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 230
 231         &sensor_dev_attr_power1_input.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         &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
 239
 240         NULL,
 241 };
 242
 243 static const struct attribute_group ltc4215_group = {
 244         .attrs = ltc4215_attributes,
 245 };
 246
 247 static int ltc4215_probe(struct i2c_client *client,
 248                          const struct i2c_device_id *id)
 249 {
 250         struct i2c_adapter *adapter = client->adapter;
 251         struct ltc4215_data *data;
 252         int ret;
 253
 254         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 255                 return -ENODEV;
 256
 257         data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 258         if (!data)
 259                 return -ENOMEM;
 260
 261         i2c_set_clientdata(client, data);
 262         mutex_init(&data->update_lock);
 263
 264         /* Initialize the LTC4215 chip */
 265         i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
 266
 267         /* Register sysfs hooks */
 268         ret = sysfs_create_group(&client->dev.kobj, &ltc4215_group);
 269         if (ret)
 270                 return ret;
 271
 272         data->hwmon_dev = hwmon_device_register(&client->dev);
 273         if (IS_ERR(data->hwmon_dev)) {
 274                 ret = PTR_ERR(data->hwmon_dev);
 275                 goto out_hwmon_device_register;
 276         }
 277
 278         return 0;
 279
 280 out_hwmon_device_register:
 281         sysfs_remove_group(&client->dev.kobj, &ltc4215_group);
 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         return 0;
 293 }
 294
 295 static const struct i2c_device_id ltc4215_id[] = {
 296         { "ltc4215", 0 },
 297         { }
 298 };
 299 MODULE_DEVICE_TABLE(i2c, ltc4215_id);
 300
 301 /* This is the driver that will be inserted */
 302 static struct i2c_driver ltc4215_driver = {
 303         .driver = {
 304                 .name   = "ltc4215",
 305         },
 306         .probe          = ltc4215_probe,
 307         .remove         = ltc4215_remove,
 308         .id_table       = ltc4215_id,
 309 };
 310
 311 module_i2c_driver(ltc4215_driver);
 312
 313 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 314 MODULE_DESCRIPTION("LTC4215 driver");
 315 MODULE_LICENSE("GPL");