drivers/iio/adc/ltc2497.c

   1 /*
   2  * ltc2497.c - Driver for Analog Devices/Linear Technology LTC2497 ADC
   3  *
   4  * Copyright (C) 2017 Analog Devices Inc.
   5  *
   6  * Licensed under the GPL-2.
   7  *
   8  * Datasheet: http://cds.linear.com/docs/en/datasheet/2497fd.pdf
   9  */
  10
  11 #include <linux/delay.h>
  12 #include <linux/i2c.h>
  13 #include <linux/iio/iio.h>
  14 #include <linux/iio/sysfs.h>
  15 #include <linux/module.h>
  16 #include <linux/of.h>
  17 #include <linux/regulator/consumer.h>
  18
  19 #define LTC2497_ENABLE                  0xA0
  20 #define LTC2497_SGL                     BIT(4)
  21 #define LTC2497_DIFF                    0
  22 #define LTC2497_SIGN                    BIT(3)
  23 #define LTC2497_CONFIG_DEFAULT          LTC2497_ENABLE
  24 #define LTC2497_CONVERSION_TIME_MS      150ULL
  25
  26 struct ltc2497_st {
  27         struct i2c_client *client;
  28         struct regulator *ref;
  29         ktime_t time_prev;
  30         u8 addr_prev;
  31         /*
  32          * DMA (thus cache coherency maintenance) requires the
  33          * transfer buffers to live in their own cache lines.
  34          */
  35         __be32 buf ____cacheline_aligned;
  36 };
  37
  38 static int ltc2497_wait_conv(struct ltc2497_st *st)
  39 {
  40         s64 time_elapsed;
  41
  42         time_elapsed = ktime_ms_delta(ktime_get(), st->time_prev);
  43
  44         if (time_elapsed < LTC2497_CONVERSION_TIME_MS) {
  45                 /* delay if conversion time not passed
  46                  * since last read or write
  47                  */
  48                 if (msleep_interruptible(
  49                     LTC2497_CONVERSION_TIME_MS - time_elapsed))
  50                         return -ERESTARTSYS;
  51
  52                 return 0;
  53         }
  54
  55         if (time_elapsed - LTC2497_CONVERSION_TIME_MS <= 0) {
  56                 /* We're in automatic mode -
  57                  * so the last reading is stil not outdated
  58                  */
  59                 return 0;
  60         }
  61
  62         return 1;
  63 }
  64
  65 static int ltc2497_read(struct ltc2497_st *st, u8 address, int *val)
  66 {
  67         struct i2c_client *client = st->client;
  68         int ret;
  69
  70         ret = ltc2497_wait_conv(st);
  71         if (ret < 0)
  72                 return ret;
  73
  74         if (ret || st->addr_prev != address) {
  75                 ret = i2c_smbus_write_byte(st->client,
  76                                            LTC2497_ENABLE | address);
  77                 if (ret < 0)
  78                         return ret;
  79                 st->addr_prev = address;
  80                 if (msleep_interruptible(LTC2497_CONVERSION_TIME_MS))
  81                         return -ERESTARTSYS;
  82         }
  83         ret = i2c_master_recv(client, (char *)&st->buf, 3);
  84         if (ret < 0)  {
  85                 dev_err(&client->dev, "i2c_master_recv failed\n");
  86                 return ret;
  87         }
  88         st->time_prev = ktime_get();
  89
  90         /* convert and shift the result,
  91          * and finally convert from offset binary to signed integer
  92          */
  93         *val = (be32_to_cpu(st->buf) >> 14) - (1 << 17);
  94
  95         return ret;
  96 }
  97
  98 static int ltc2497_read_raw(struct iio_dev *indio_dev,
  99                             struct iio_chan_spec const *chan,
 100                             int *val, int *val2, long mask)
 101 {
 102         struct ltc2497_st *st = iio_priv(indio_dev);
 103         int ret;
 104
 105         switch (mask) {
 106         case IIO_CHAN_INFO_RAW:
 107                 mutex_lock(&indio_dev->mlock);
 108                 ret = ltc2497_read(st, chan->address, val);
 109                 mutex_unlock(&indio_dev->mlock);
 110                 if (ret < 0)
 111                         return ret;
 112
 113                 return IIO_VAL_INT;
 114
 115         case IIO_CHAN_INFO_SCALE:
 116                 ret = regulator_get_voltage(st->ref);
 117                 if (ret < 0)
 118                         return ret;
 119
 120                 *val = ret / 1000;
 121                 *val2 = 17;
 122
 123                 return IIO_VAL_FRACTIONAL_LOG2;
 124
 125         default:
 126                 return -EINVAL;
 127         }
 128 }
 129
 130 #define LTC2497_CHAN(_chan, _addr) { \
 131         .type = IIO_VOLTAGE, \
 132         .indexed = 1, \
 133         .channel = (_chan), \
 134         .address = (_addr | (_chan / 2) | ((_chan & 1) ? LTC2497_SIGN : 0)), \
 135         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
 136         .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
 137 }
 138
 139 #define LTC2497_CHAN_DIFF(_chan, _addr) { \
 140         .type = IIO_VOLTAGE, \
 141         .indexed = 1, \
 142         .channel = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 1 : 0), \
 143         .channel2 = (_chan) * 2 + ((_addr) & LTC2497_SIGN ? 0 : 1),\
 144         .address = (_addr | _chan), \
 145         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
 146         .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
 147         .differential = 1, \
 148 }
 149
 150 static const struct iio_chan_spec ltc2497_channel[] = {
 151         LTC2497_CHAN(0, LTC2497_SGL),
 152         LTC2497_CHAN(1, LTC2497_SGL),
 153         LTC2497_CHAN(2, LTC2497_SGL),
 154         LTC2497_CHAN(3, LTC2497_SGL),
 155         LTC2497_CHAN(4, LTC2497_SGL),
 156         LTC2497_CHAN(5, LTC2497_SGL),
 157         LTC2497_CHAN(6, LTC2497_SGL),
 158         LTC2497_CHAN(7, LTC2497_SGL),
 159         LTC2497_CHAN(8, LTC2497_SGL),
 160         LTC2497_CHAN(9, LTC2497_SGL),
 161         LTC2497_CHAN(10, LTC2497_SGL),
 162         LTC2497_CHAN(11, LTC2497_SGL),
 163         LTC2497_CHAN(12, LTC2497_SGL),
 164         LTC2497_CHAN(13, LTC2497_SGL),
 165         LTC2497_CHAN(14, LTC2497_SGL),
 166         LTC2497_CHAN(15, LTC2497_SGL),
 167         LTC2497_CHAN_DIFF(0, LTC2497_DIFF),
 168         LTC2497_CHAN_DIFF(1, LTC2497_DIFF),
 169         LTC2497_CHAN_DIFF(2, LTC2497_DIFF),
 170         LTC2497_CHAN_DIFF(3, LTC2497_DIFF),
 171         LTC2497_CHAN_DIFF(4, LTC2497_DIFF),
 172         LTC2497_CHAN_DIFF(5, LTC2497_DIFF),
 173         LTC2497_CHAN_DIFF(6, LTC2497_DIFF),
 174         LTC2497_CHAN_DIFF(7, LTC2497_DIFF),
 175         LTC2497_CHAN_DIFF(0, LTC2497_DIFF | LTC2497_SIGN),
 176         LTC2497_CHAN_DIFF(1, LTC2497_DIFF | LTC2497_SIGN),
 177         LTC2497_CHAN_DIFF(2, LTC2497_DIFF | LTC2497_SIGN),
 178         LTC2497_CHAN_DIFF(3, LTC2497_DIFF | LTC2497_SIGN),
 179         LTC2497_CHAN_DIFF(4, LTC2497_DIFF | LTC2497_SIGN),
 180         LTC2497_CHAN_DIFF(5, LTC2497_DIFF | LTC2497_SIGN),
 181         LTC2497_CHAN_DIFF(6, LTC2497_DIFF | LTC2497_SIGN),
 182         LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN),
 183 };
 184
 185 static const struct iio_info ltc2497_info = {
 186         .read_raw = ltc2497_read_raw,
 187         .driver_module = THIS_MODULE,
 188 };
 189
 190 static int ltc2497_probe(struct i2c_client *client,
 191                          const struct i2c_device_id *id)
 192 {
 193         struct iio_dev *indio_dev;
 194         struct ltc2497_st *st;
 195         int ret;
 196
 197         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
 198                                      I2C_FUNC_SMBUS_WRITE_BYTE))
 199                 return -EOPNOTSUPP;
 200
 201         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*st));
 202         if (!indio_dev)
 203                 return -ENOMEM;
 204
 205         st = iio_priv(indio_dev);
 206         i2c_set_clientdata(client, indio_dev);
 207         st->client = client;
 208
 209         indio_dev->dev.parent = &client->dev;
 210         indio_dev->name = id->name;
 211         indio_dev->info = &ltc2497_info;
 212         indio_dev->modes = INDIO_DIRECT_MODE;
 213         indio_dev->channels = ltc2497_channel;
 214         indio_dev->num_channels = ARRAY_SIZE(ltc2497_channel);
 215
 216         st->ref = devm_regulator_get(&client->dev, "vref");
 217         if (IS_ERR(st->ref))
 218                 return PTR_ERR(st->ref);
 219
 220         ret = regulator_enable(st->ref);
 221         if (ret < 0)
 222                 return ret;
 223
 224         ret = i2c_smbus_write_byte(st->client, LTC2497_CONFIG_DEFAULT);
 225         if (ret < 0)
 226                 goto err_regulator_disable;
 227
 228         st->addr_prev = LTC2497_CONFIG_DEFAULT;
 229         st->time_prev = ktime_get();
 230
 231         ret = iio_device_register(indio_dev);
 232         if (ret < 0)
 233                 goto err_regulator_disable;
 234
 235         return 0;
 236
 237 err_regulator_disable:
 238         regulator_disable(st->ref);
 239
 240         return ret;
 241 }
 242
 243 static int ltc2497_remove(struct i2c_client *client)
 244 {
 245         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 246         struct ltc2497_st *st = iio_priv(indio_dev);
 247
 248         iio_device_unregister(indio_dev);
 249         regulator_disable(st->ref);
 250
 251         return 0;
 252 }
 253
 254 static const struct i2c_device_id ltc2497_id[] = {
 255         { "ltc2497", 0 },
 256         { }
 257 };
 258 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
 259
 260 static const struct of_device_id ltc2497_of_match[] = {
 261         { .compatible = "lltc,ltc2497", },
 262         {},
 263 };
 264 MODULE_DEVICE_TABLE(of, ltc2497_of_match);
 265
 266 static struct i2c_driver ltc2497_driver = {
 267         .driver = {
 268                 .name = "ltc2497",
 269                 .of_match_table = of_match_ptr(ltc2497_of_match),
 270         },
 271         .probe = ltc2497_probe,
 272         .remove = ltc2497_remove,
 273         .id_table = ltc2497_id,
 274 };
 275 module_i2c_driver(ltc2497_driver);
 276
 277 MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
 278 MODULE_DESCRIPTION("Linear Technology LTC2497 ADC driver");
 279 MODULE_LICENSE("GPL v2");