linux/drivers/hwmon/ltc4261.c
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   1/*
   2 * Driver for Linear Technology LTC4261 I2C Negative Voltage Hot Swap Controller
   3 *
   4 * Copyright (C) 2010 Ericsson AB.
   5 *
   6 * Derived from:
   7 *
   8 *  Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
   9 *  Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
  10 *
  11 * Datasheet: http://cds.linear.com/docs/Datasheet/42612fb.pdf
  12 *
  13 * This program is free software; you can redistribute it and/or modify
  14 * it under the terms of the GNU General Public License as published by
  15 * the Free Software Foundation; either version 2 of the License, or
  16 * (at your option) any later version.
  17 *
  18 * This program is distributed in the hope that it will be useful,
  19 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 * GNU General Public License for more details.
  22 *
  23 * You should have received a copy of the GNU General Public License
  24 * along with this program; if not, write to the Free Software
  25 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  26 */
  27
  28#include <linux/kernel.h>
  29#include <linux/module.h>
  30#include <linux/init.h>
  31#include <linux/err.h>
  32#include <linux/slab.h>
  33#include <linux/i2c.h>
  34#include <linux/hwmon.h>
  35#include <linux/hwmon-sysfs.h>
  36#include <linux/jiffies.h>
  37
  38/* chip registers */
  39#define LTC4261_STATUS  0x00    /* readonly */
  40#define LTC4261_FAULT   0x01
  41#define LTC4261_ALERT   0x02
  42#define LTC4261_CONTROL 0x03
  43#define LTC4261_SENSE_H 0x04
  44#define LTC4261_SENSE_L 0x05
  45#define LTC4261_ADIN2_H 0x06
  46#define LTC4261_ADIN2_L 0x07
  47#define LTC4261_ADIN_H  0x08
  48#define LTC4261_ADIN_L  0x09
  49
  50/*
  51 * Fault register bits
  52 */
  53#define FAULT_OV        (1<<0)
  54#define FAULT_UV        (1<<1)
  55#define FAULT_OC        (1<<2)
  56
  57struct ltc4261_data {
  58        struct device *hwmon_dev;
  59
  60        struct mutex update_lock;
  61        bool valid;
  62        unsigned long last_updated;     /* in jiffies */
  63
  64        /* Registers */
  65        u8 regs[10];
  66};
  67
  68static struct ltc4261_data *ltc4261_update_device(struct device *dev)
  69{
  70        struct i2c_client *client = to_i2c_client(dev);
  71        struct ltc4261_data *data = i2c_get_clientdata(client);
  72        struct ltc4261_data *ret = data;
  73
  74        mutex_lock(&data->update_lock);
  75
  76        if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
  77                int i;
  78
  79                /* Read registers -- 0x00 to 0x09 */
  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                                data->valid = 0;
  90                                goto abort;
  91                        }
  92                        data->regs[i] = val;
  93                }
  94                data->last_updated = jiffies;
  95                data->valid = 1;
  96        }
  97abort:
  98        mutex_unlock(&data->update_lock);
  99        return ret;
 100}
 101
 102/* Return the voltage from the given register in mV or mA */
 103static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)
 104{
 105        u32 val;
 106
 107        val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);
 108
 109        switch (reg) {
 110        case LTC4261_ADIN_H:
 111        case LTC4261_ADIN2_H:
 112                /* 2.5mV resolution. Convert to mV. */
 113                val = val * 25 / 10;
 114                break;
 115        case LTC4261_SENSE_H:
 116                /*
 117                 * 62.5uV resolution. Convert to current as measured with
 118                 * an 1 mOhm sense resistor, in mA. If a different sense
 119                 * resistor is installed, calculate the actual current by
 120                 * dividing the reported current by the sense resistor value
 121                 * in mOhm.
 122                 */
 123                val = val * 625 / 10;
 124                break;
 125        default:
 126                /* If we get here, the developer messed up */
 127                WARN_ON_ONCE(1);
 128                val = 0;
 129                break;
 130        }
 131
 132        return val;
 133}
 134
 135static ssize_t ltc4261_show_value(struct device *dev,
 136                                  struct device_attribute *da, char *buf)
 137{
 138        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 139        struct ltc4261_data *data = ltc4261_update_device(dev);
 140        int value;
 141
 142        if (IS_ERR(data))
 143                return PTR_ERR(data);
 144
 145        value = ltc4261_get_value(data, attr->index);
 146        return snprintf(buf, PAGE_SIZE, "%d\n", value);
 147}
 148
 149static ssize_t ltc4261_show_bool(struct device *dev,
 150                                 struct device_attribute *da, char *buf)
 151{
 152        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 153        struct i2c_client *client = to_i2c_client(dev);
 154        struct ltc4261_data *data = ltc4261_update_device(dev);
 155        u8 fault;
 156
 157        if (IS_ERR(data))
 158                return PTR_ERR(data);
 159
 160        fault = data->regs[LTC4261_FAULT] & attr->index;
 161        if (fault)              /* Clear reported faults in chip register */
 162                i2c_smbus_write_byte_data(client, LTC4261_FAULT, ~fault);
 163
 164        return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);
 165}
 166
 167/*
 168 * Input voltages.
 169 */
 170static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4261_show_value, NULL,
 171                          LTC4261_ADIN_H);
 172static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4261_show_value, NULL,
 173                          LTC4261_ADIN2_H);
 174
 175/*
 176 * Voltage alarms. The chip has only one set of voltage alarm status bits,
 177 * triggered by input voltage alarms. In many designs, those alarms are
 178 * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
 179 * to the OV pin. ADIN2 is, however, not available on all chip variants.
 180 * To ensure that the alarm condition is reported to the user, report it
 181 * with both voltage sensors.
 182 */
 183static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4261_show_bool, NULL,
 184                          FAULT_UV);
 185static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4261_show_bool, NULL,
 186                          FAULT_OV);
 187static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4261_show_bool, NULL,
 188                          FAULT_UV);
 189static SENSOR_DEVICE_ATTR(in2_max_alarm, S_IRUGO, ltc4261_show_bool, NULL,
 190                          FAULT_OV);
 191
 192/* Currents (via sense resistor) */
 193static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4261_show_value, NULL,
 194                          LTC4261_SENSE_H);
 195
 196/* Overcurrent alarm */
 197static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4261_show_bool, NULL,
 198                          FAULT_OC);
 199
 200static struct attribute *ltc4261_attributes[] = {
 201        &sensor_dev_attr_in1_input.dev_attr.attr,
 202        &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
 203        &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
 204        &sensor_dev_attr_in2_input.dev_attr.attr,
 205        &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
 206        &sensor_dev_attr_in2_max_alarm.dev_attr.attr,
 207
 208        &sensor_dev_attr_curr1_input.dev_attr.attr,
 209        &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 210
 211        NULL,
 212};
 213
 214static const struct attribute_group ltc4261_group = {
 215        .attrs = ltc4261_attributes,
 216};
 217
 218static int ltc4261_probe(struct i2c_client *client,
 219                         const struct i2c_device_id *id)
 220{
 221        struct i2c_adapter *adapter = client->adapter;
 222        struct ltc4261_data *data;
 223        int ret;
 224
 225        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 226                return -ENODEV;
 227
 228        if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {
 229                dev_err(&client->dev, "Failed to read status register\n");
 230                return -ENODEV;
 231        }
 232
 233        data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 234        if (!data)
 235                return -ENOMEM;
 236
 237        i2c_set_clientdata(client, data);
 238        mutex_init(&data->update_lock);
 239
 240        /* Clear faults */
 241        i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);
 242
 243        /* Register sysfs hooks */
 244        ret = sysfs_create_group(&client->dev.kobj, &ltc4261_group);
 245        if (ret)
 246                return ret;
 247
 248        data->hwmon_dev = hwmon_device_register(&client->dev);
 249        if (IS_ERR(data->hwmon_dev)) {
 250                ret = PTR_ERR(data->hwmon_dev);
 251                goto out_hwmon_device_register;
 252        }
 253
 254        return 0;
 255
 256out_hwmon_device_register:
 257        sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
 258        return ret;
 259}
 260
 261static int ltc4261_remove(struct i2c_client *client)
 262{
 263        struct ltc4261_data *data = i2c_get_clientdata(client);
 264
 265        hwmon_device_unregister(data->hwmon_dev);
 266        sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
 267
 268        return 0;
 269}
 270
 271static const struct i2c_device_id ltc4261_id[] = {
 272        {"ltc4261", 0},
 273        {}
 274};
 275
 276MODULE_DEVICE_TABLE(i2c, ltc4261_id);
 277
 278/* This is the driver that will be inserted */
 279static struct i2c_driver ltc4261_driver = {
 280        .driver = {
 281                   .name = "ltc4261",
 282                   },
 283        .probe = ltc4261_probe,
 284        .remove = ltc4261_remove,
 285        .id_table = ltc4261_id,
 286};
 287
 288module_i2c_driver(ltc4261_driver);
 289
 290MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
 291MODULE_DESCRIPTION("LTC4261 driver");
 292MODULE_LICENSE("GPL");
 293
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