drivers/hwmon/ltc4151.c

   1 /*
   2  * Driver for Linear Technology LTC4151 High Voltage I2C Current
   3  * and Voltage Monitor
   4  *
   5  * Copyright (C) 2011 AppearTV AS
   6  *
   7  * Derived from:
   8  *
   9  *  Driver for Linear Technology LTC4261 I2C Negative Voltage Hot
  10  *  Swap Controller
  11  *  Copyright (C) 2010 Ericsson AB.
  12  *
  13  * Datasheet: http://www.linear.com/docs/Datasheet/4151fc.pdf
  14  *
  15  * This program is free software; you can redistribute it and/or modify
  16  * it under the terms of the GNU General Public License as published by
  17  * the Free Software Foundation; either version 2 of the License, or
  18  * (at your option) any later version.
  19  *
  20  * This program is distributed in the hope that it will be useful,
  21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23  * GNU General Public License for more details.
  24  *
  25  * You should have received a copy of the GNU General Public License
  26  * along with this program; if not, write to the Free Software
  27  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  28  *
  29  */
  30
  31 #include <linux/kernel.h>
  32 #include <linux/module.h>
  33 #include <linux/of.h>
  34 #include <linux/init.h>
  35 #include <linux/err.h>
  36 #include <linux/slab.h>
  37 #include <linux/i2c.h>
  38 #include <linux/hwmon.h>
  39 #include <linux/hwmon-sysfs.h>
  40 #include <linux/jiffies.h>
  41
  42 /* chip registers */
  43 #define LTC4151_SENSE_H 0x00
  44 #define LTC4151_SENSE_L 0x01
  45 #define LTC4151_VIN_H   0x02
  46 #define LTC4151_VIN_L   0x03
  47 #define LTC4151_ADIN_H  0x04
  48 #define LTC4151_ADIN_L  0x05
  49
  50 struct ltc4151_data {
  51         struct i2c_client *client;
  52
  53         struct mutex update_lock;
  54         bool valid;
  55         unsigned long last_updated; /* in jiffies */
  56         unsigned int shunt; /* in micro ohms */
  57
  58         /* Registers */
  59         u8 regs[6];
  60 };
  61
  62 static struct ltc4151_data *ltc4151_update_device(struct device *dev)
  63 {
  64         struct ltc4151_data *data = dev_get_drvdata(dev);
  65         struct i2c_client *client = data->client;
  66         struct ltc4151_data *ret = data;
  67
  68         mutex_lock(&data->update_lock);
  69
  70         /*
  71          * The chip's A/D updates 6 times per second
  72          * (Conversion Rate 6 - 9 Hz)
  73          */
  74         if (time_after(jiffies, data->last_updated + HZ / 6) || !data->valid) {
  75                 int i;
  76
  77                 dev_dbg(&client->dev, "Starting ltc4151 update\n");
  78
  79                 /* Read all registers */
  80                 for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
  81                         int val;
  82
  83                         val = i2c_smbus_read_byte_data(client, i);
  84                         if (unlikely(val < 0)) {
  85                                 dev_dbg(dev,
  86                                         "Failed to read ADC value: error %d\n",
  87                                         val);
  88                                 ret = ERR_PTR(val);
  89                                 goto abort;
  90                         }
  91                         data->regs[i] = val;
  92                 }
  93                 data->last_updated = jiffies;
  94                 data->valid = 1;
  95         }
  96 abort:
  97         mutex_unlock(&data->update_lock);
  98         return ret;
  99 }
 100
 101 /* Return the voltage from the given register in mV */
 102 static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
 103 {
 104         u32 val;
 105
 106         val = (data->regs[reg] << 4) + (data->regs[reg + 1] >> 4);
 107
 108         switch (reg) {
 109         case LTC4151_ADIN_H:
 110                 /* 500uV resolution. Convert to mV. */
 111                 val = val * 500 / 1000;
 112                 break;
 113         case LTC4151_SENSE_H:
 114                 /*
 115                  * 20uV resolution. Convert to current as measured with
 116                  * a given sense resistor, in mA.
 117                  */
 118                 val = val * 20 * 1000 / data->shunt;
 119                 break;
 120         case LTC4151_VIN_H:
 121                 /* 25 mV per increment */
 122                 val = val * 25;
 123                 break;
 124         default:
 125                 /* If we get here, the developer messed up */
 126                 WARN_ON_ONCE(1);
 127                 val = 0;
 128                 break;
 129         }
 130
 131         return val;
 132 }
 133
 134 static ssize_t ltc4151_show_value(struct device *dev,
 135                                   struct device_attribute *da, char *buf)
 136 {
 137         struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 138         struct ltc4151_data *data = ltc4151_update_device(dev);
 139         int value;
 140
 141         if (IS_ERR(data))
 142                 return PTR_ERR(data);
 143
 144         value = ltc4151_get_value(data, attr->index);
 145         return snprintf(buf, PAGE_SIZE, "%d\n", value);
 146 }
 147
 148 /*
 149  * Input voltages.
 150  */
 151 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4151_show_value, NULL,
 152                           LTC4151_VIN_H);
 153 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4151_show_value, NULL,
 154                           LTC4151_ADIN_H);
 155
 156 /* Currents (via sense resistor) */
 157 static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4151_show_value, NULL,
 158                           LTC4151_SENSE_H);
 159
 160 /*
 161  * Finally, construct an array of pointers to members of the above objects,
 162  * as required for sysfs_create_group()
 163  */
 164 static struct attribute *ltc4151_attrs[] = {
 165         &sensor_dev_attr_in1_input.dev_attr.attr,
 166         &sensor_dev_attr_in2_input.dev_attr.attr,
 167
 168         &sensor_dev_attr_curr1_input.dev_attr.attr,
 169
 170         NULL,
 171 };
 172 ATTRIBUTE_GROUPS(ltc4151);
 173
 174 static int ltc4151_probe(struct i2c_client *client,
 175                          const struct i2c_device_id *id)
 176 {
 177         struct i2c_adapter *adapter = client->adapter;
 178         struct device *dev = &client->dev;
 179         struct ltc4151_data *data;
 180         struct device *hwmon_dev;
 181         u32 shunt;
 182
 183         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 184                 return -ENODEV;
 185
 186         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 187         if (!data)
 188                 return -ENOMEM;
 189
 190         if (of_property_read_u32(client->dev.of_node,
 191                                  "shunt-resistor-micro-ohms", &shunt))
 192                 shunt = 1000; /* 1 mOhm if not set via DT */
 193
 194         if (shunt == 0)
 195                 return -EINVAL;
 196
 197         data->shunt = shunt;
 198
 199         data->client = client;
 200         mutex_init(&data->update_lock);
 201
 202         hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 203                                                            data,
 204                                                            ltc4151_groups);
 205         return PTR_ERR_OR_ZERO(hwmon_dev);
 206 }
 207
 208 static const struct i2c_device_id ltc4151_id[] = {
 209         { "ltc4151", 0 },
 210         { }
 211 };
 212 MODULE_DEVICE_TABLE(i2c, ltc4151_id);
 213
 214 static const struct of_device_id ltc4151_match[] = {
 215         { .compatible = "lltc,ltc4151" },
 216         {},
 217 };
 218 MODULE_DEVICE_TABLE(of, ltc4151_match);
 219
 220 /* This is the driver that will be inserted */
 221 static struct i2c_driver ltc4151_driver = {
 222         .driver = {
 223                 .name   = "ltc4151",
 224                 .of_match_table = of_match_ptr(ltc4151_match),
 225         },
 226         .probe          = ltc4151_probe,
 227         .id_table       = ltc4151_id,
 228 };
 229
 230 module_i2c_driver(ltc4151_driver);
 231
 232 MODULE_AUTHOR("Per Dalen <per.dalen@appeartv.com>");
 233 MODULE_DESCRIPTION("LTC4151 driver");
 234 MODULE_LICENSE("GPL");