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
  37/* chip registers */
  38#define LTC4261_STATUS  0x00    /* readonly */
  39#define LTC4261_FAULT   0x01
  40#define LTC4261_ALERT   0x02
  41#define LTC4261_CONTROL 0x03
  42#define LTC4261_SENSE_H 0x04
  43#define LTC4261_SENSE_L 0x05
  44#define LTC4261_ADIN2_H 0x06
  45#define LTC4261_ADIN2_L 0x07
  46#define LTC4261_ADIN_H  0x08
  47#define LTC4261_ADIN_L  0x09
  48
  49/*
  50 * Fault register bits
  51 */
  52#define FAULT_OV        (1<<0)
  53#define FAULT_UV        (1<<1)
  54#define FAULT_OC        (1<<2)
  55
  56struct ltc4261_data {
  57        struct device *hwmon_dev;
  58
  59        struct mutex update_lock;
  60        bool valid;
  61        unsigned long last_updated;     /* in jiffies */
  62
  63        /* Registers */
  64        u8 regs[10];
  65};
  66
  67static struct ltc4261_data *ltc4261_update_device(struct device *dev)
  68{
  69        struct i2c_client *client = to_i2c_client(dev);
  70        struct ltc4261_data *data = i2c_get_clientdata(client);
  71        struct ltc4261_data *ret = data;
  72
  73        mutex_lock(&data->update_lock);
  74
  75        if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
  76                int i;
  77
  78                /* Read registers -- 0x00 to 0x09 */
  79                for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
  80                        int val;
  81
  82                        val = i2c_smbus_read_byte_data(client, i);
  83                        if (unlikely(val < 0)) {
  84                                dev_dbg(dev,
  85                                        "Failed to read ADC value: error %d\n",
  86                                        val);
  87                                ret = ERR_PTR(val);
  88                                data->valid = 0;
  89                                goto abort;
  90                        }
  91                        data->regs[i] = val;
  92                }
  93                data->last_updated = jiffies;
  94                data->valid = 1;
  95        }
  96abort:
  97        mutex_unlock(&data->update_lock);
  98        return ret;
  99}
 100
 101/* Return the voltage from the given register in mV or mA */
 102static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)
 103{
 104        u32 val;
 105
 106        val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);
 107
 108        switch (reg) {
 109        case LTC4261_ADIN_H:
 110        case LTC4261_ADIN2_H:
 111                /* 2.5mV resolution. Convert to mV. */
 112                val = val * 25 / 10;
 113                break;
 114        case LTC4261_SENSE_H:
 115                /*
 116                 * 62.5uV resolution. Convert to current as measured with
 117                 * an 1 mOhm sense resistor, in mA. If a different sense
 118                 * resistor is installed, calculate the actual current by
 119                 * dividing the reported current by the sense resistor value
 120                 * in mOhm.
 121                 */
 122                val = val * 625 / 10;
 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
 134static ssize_t ltc4261_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 ltc4261_data *data = ltc4261_update_device(dev);
 139        int value;
 140
 141        if (IS_ERR(data))
 142                return PTR_ERR(data);
 143
 144        value = ltc4261_get_value(data, attr->index);
 145        return snprintf(buf, PAGE_SIZE, "%d\n", value);
 146}
 147
 148static ssize_t ltc4261_show_bool(struct device *dev,
 149                                 struct device_attribute *da, char *buf)
 150{
 151        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 152        struct i2c_client *client = to_i2c_client(dev);
 153        struct ltc4261_data *data = ltc4261_update_device(dev);
 154        u8 fault;
 155
 156        if (IS_ERR(data))
 157                return PTR_ERR(data);
 158
 159        fault = data->regs[LTC4261_FAULT] & attr->index;
 160        if (fault)              /* Clear reported faults in chip register */
 161                i2c_smbus_write_byte_data(client, LTC4261_FAULT, ~fault);
 162
 163        return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);
 164}
 165
 166/*
 167 * These macros are used below in constructing device attribute objects
 168 * for use with sysfs_create_group() to make a sysfs device file
 169 * for each register.
 170 */
 171
 172#define LTC4261_VALUE(name, ltc4261_cmd_idx) \
 173        static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 174        ltc4261_show_value, NULL, ltc4261_cmd_idx)
 175
 176#define LTC4261_BOOL(name, mask) \
 177        static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 178        ltc4261_show_bool, NULL, (mask))
 179
 180/*
 181 * Input voltages.
 182 */
 183LTC4261_VALUE(in1_input, LTC4261_ADIN_H);
 184LTC4261_VALUE(in2_input, LTC4261_ADIN2_H);
 185
 186/*
 187 * Voltage alarms. The chip has only one set of voltage alarm status bits,
 188 * triggered by input voltage alarms. In many designs, those alarms are
 189 * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
 190 * to the OV pin. ADIN2 is, however, not available on all chip variants.
 191 * To ensure that the alarm condition is reported to the user, report it
 192 * with both voltage sensors.
 193 */
 194LTC4261_BOOL(in1_min_alarm, FAULT_UV);
 195LTC4261_BOOL(in1_max_alarm, FAULT_OV);
 196LTC4261_BOOL(in2_min_alarm, FAULT_UV);
 197LTC4261_BOOL(in2_max_alarm, FAULT_OV);
 198
 199/* Currents (via sense resistor) */
 200LTC4261_VALUE(curr1_input, LTC4261_SENSE_H);
 201
 202/* Overcurrent alarm */
 203LTC4261_BOOL(curr1_max_alarm, FAULT_OC);
 204
 205static struct attribute *ltc4261_attributes[] = {
 206        &sensor_dev_attr_in1_input.dev_attr.attr,
 207        &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
 208        &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
 209        &sensor_dev_attr_in2_input.dev_attr.attr,
 210        &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
 211        &sensor_dev_attr_in2_max_alarm.dev_attr.attr,
 212
 213        &sensor_dev_attr_curr1_input.dev_attr.attr,
 214        &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 215
 216        NULL,
 217};
 218
 219static const struct attribute_group ltc4261_group = {
 220        .attrs = ltc4261_attributes,
 221};
 222
 223static int ltc4261_probe(struct i2c_client *client,
 224                         const struct i2c_device_id *id)
 225{
 226        struct i2c_adapter *adapter = client->adapter;
 227        struct ltc4261_data *data;
 228        int ret;
 229
 230        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 231                return -ENODEV;
 232
 233        if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {
 234                dev_err(&client->dev, "Failed to read status register\n");
 235                return -ENODEV;
 236        }
 237
 238        data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
 239        if (!data)
 240                return -ENOMEM;
 241
 242        i2c_set_clientdata(client, data);
 243        mutex_init(&data->update_lock);
 244
 245        /* Clear faults */
 246        i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);
 247
 248        /* Register sysfs hooks */
 249        ret = sysfs_create_group(&client->dev.kobj, &ltc4261_group);
 250        if (ret)
 251                return ret;
 252
 253        data->hwmon_dev = hwmon_device_register(&client->dev);
 254        if (IS_ERR(data->hwmon_dev)) {
 255                ret = PTR_ERR(data->hwmon_dev);
 256                goto out_hwmon_device_register;
 257        }
 258
 259        return 0;
 260
 261out_hwmon_device_register:
 262        sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
 263        return ret;
 264}
 265
 266static int ltc4261_remove(struct i2c_client *client)
 267{
 268        struct ltc4261_data *data = i2c_get_clientdata(client);
 269
 270        hwmon_device_unregister(data->hwmon_dev);
 271        sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
 272
 273        return 0;
 274}
 275
 276static const struct i2c_device_id ltc4261_id[] = {
 277        {"ltc4261", 0},
 278        {}
 279};
 280
 281MODULE_DEVICE_TABLE(i2c, ltc4261_id);
 282
 283/* This is the driver that will be inserted */
 284static struct i2c_driver ltc4261_driver = {
 285        .driver = {
 286                   .name = "ltc4261",
 287                   },
 288        .probe = ltc4261_probe,
 289        .remove = ltc4261_remove,
 290        .id_table = ltc4261_id,
 291};
 292
 293module_i2c_driver(ltc4261_driver);
 294
 295MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
 296MODULE_DESCRIPTION("LTC4261 driver");
 297MODULE_LICENSE("GPL");
 298
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