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 i2c_client *client;
  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 ltc4215_data *data = dev_get_drvdata(dev);
  49         struct i2c_client *client = data->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 *attr = to_sensor_dev_attr(da);
 176         struct ltc4215_data *data = ltc4215_update_device(dev);
 177         const u8 reg = data->regs[LTC4215_STATUS];
 178         const u32 mask = attr->index;
 179
 180         return snprintf(buf, PAGE_SIZE, "%u\n", !!(reg & mask));
 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 /* Construct a sensor_device_attribute structure for each register */
 190
 191 /* Current */
 192 static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4215_show_current, NULL, 0);
 193 static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
 194                           1 << 2);
 195
 196 /* Power (virtual) */
 197 static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ltc4215_show_power, NULL, 0);
 198
 199 /* Input Voltage */
 200 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4215_show_voltage, NULL,
 201                           LTC4215_ADIN);
 202 static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
 203                           1 << 0);
 204 static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
 205                           1 << 1);
 206
 207 /* Output Voltage */
 208 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4215_show_voltage, NULL,
 209                           LTC4215_SOURCE);
 210 static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL,
 211                           1 << 3);
 212
 213 /*
 214  * Finally, construct an array of pointers to members of the above objects,
 215  * as required for sysfs_create_group()
 216  */
 217 static struct attribute *ltc4215_attrs[] = {
 218         &sensor_dev_attr_curr1_input.dev_attr.attr,
 219         &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 220
 221         &sensor_dev_attr_power1_input.dev_attr.attr,
 222
 223         &sensor_dev_attr_in1_input.dev_attr.attr,
 224         &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
 225         &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
 226
 227         &sensor_dev_attr_in2_input.dev_attr.attr,
 228         &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
 229
 230         NULL,
 231 };
 232 ATTRIBUTE_GROUPS(ltc4215);
 233
 234 static int ltc4215_probe(struct i2c_client *client,
 235                          const struct i2c_device_id *id)
 236 {
 237         struct i2c_adapter *adapter = client->adapter;
 238         struct device *dev = &client->dev;
 239         struct ltc4215_data *data;
 240         struct device *hwmon_dev;
 241
 242         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 243                 return -ENODEV;
 244
 245         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 246         if (!data)
 247                 return -ENOMEM;
 248
 249         data->client = client;
 250         mutex_init(&data->update_lock);
 251
 252         /* Initialize the LTC4215 chip */
 253         i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
 254
 255         hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 256                                                            data,
 257                                                            ltc4215_groups);
 258         return PTR_ERR_OR_ZERO(hwmon_dev);
 259 }
 260
 261 static const struct i2c_device_id ltc4215_id[] = {
 262         { "ltc4215", 0 },
 263         { }
 264 };
 265 MODULE_DEVICE_TABLE(i2c, ltc4215_id);
 266
 267 /* This is the driver that will be inserted */
 268 static struct i2c_driver ltc4215_driver = {
 269         .driver = {
 270                 .name   = "ltc4215",
 271         },
 272         .probe          = ltc4215_probe,
 273         .id_table       = ltc4215_id,
 274 };
 275
 276 module_i2c_driver(ltc4215_driver);
 277
 278 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 279 MODULE_DESCRIPTION("LTC4215 driver");
 280 MODULE_LICENSE("GPL");