ltc2485.c 3.3 KB

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  1. // SPDX-License-Identifier: GPL-2.0-only
  2. /*
  3. * ltc2485.c - Driver for Linear Technology LTC2485 ADC
  4. *
  5. * Copyright (C) 2016 Alison Schofield <amsfield22@gmail.com>
  6. *
  7. * Datasheet: http://cds.linear.com/docs/en/datasheet/2485fd.pdf
  8. */
  9. #include <linux/delay.h>
  10. #include <linux/i2c.h>
  11. #include <linux/module.h>
  12. #include <linux/iio/iio.h>
  13. #include <linux/iio/sysfs.h>
  14. /* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */
  15. #define LTC2485_CONFIG_DEFAULT 0
  16. struct ltc2485_data {
  17. struct i2c_client *client;
  18. ktime_t time_prev; /* last conversion */
  19. };
  20. static void ltc2485_wait_conv(struct ltc2485_data *data)
  21. {
  22. const unsigned int conv_time = 147; /* conversion time ms */
  23. unsigned int time_elapsed;
  24. /* delay if conversion time not passed since last read or write */
  25. time_elapsed = ktime_ms_delta(ktime_get(), data->time_prev);
  26. if (time_elapsed < conv_time)
  27. msleep(conv_time - time_elapsed);
  28. }
  29. static int ltc2485_read(struct ltc2485_data *data, int *val)
  30. {
  31. struct i2c_client *client = data->client;
  32. __be32 buf = 0;
  33. int ret;
  34. ltc2485_wait_conv(data);
  35. ret = i2c_master_recv(client, (char *)&buf, 4);
  36. if (ret < 0) {
  37. dev_err(&client->dev, "i2c_master_recv failed\n");
  38. return ret;
  39. }
  40. data->time_prev = ktime_get();
  41. *val = sign_extend32(be32_to_cpu(buf) >> 6, 24);
  42. return ret;
  43. }
  44. static int ltc2485_read_raw(struct iio_dev *indio_dev,
  45. struct iio_chan_spec const *chan,
  46. int *val, int *val2, long mask)
  47. {
  48. struct ltc2485_data *data = iio_priv(indio_dev);
  49. int ret;
  50. if (mask == IIO_CHAN_INFO_RAW) {
  51. ret = ltc2485_read(data, val);
  52. if (ret < 0)
  53. return ret;
  54. return IIO_VAL_INT;
  55. } else if (mask == IIO_CHAN_INFO_SCALE) {
  56. *val = 5000; /* on board vref millivolts */
  57. *val2 = 25; /* 25 (24 + sign) data bits */
  58. return IIO_VAL_FRACTIONAL_LOG2;
  59. } else {
  60. return -EINVAL;
  61. }
  62. }
  63. static const struct iio_chan_spec ltc2485_channel[] = {
  64. {
  65. .type = IIO_VOLTAGE,
  66. .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
  67. .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE)
  68. },
  69. };
  70. static const struct iio_info ltc2485_info = {
  71. .read_raw = ltc2485_read_raw,
  72. };
  73. static int ltc2485_probe(struct i2c_client *client,
  74. const struct i2c_device_id *id)
  75. {
  76. struct iio_dev *indio_dev;
  77. struct ltc2485_data *data;
  78. int ret;
  79. if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
  80. I2C_FUNC_SMBUS_WRITE_BYTE))
  81. return -EOPNOTSUPP;
  82. indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
  83. if (!indio_dev)
  84. return -ENOMEM;
  85. data = iio_priv(indio_dev);
  86. i2c_set_clientdata(client, indio_dev);
  87. data->client = client;
  88. indio_dev->name = id->name;
  89. indio_dev->info = &ltc2485_info;
  90. indio_dev->modes = INDIO_DIRECT_MODE;
  91. indio_dev->channels = ltc2485_channel;
  92. indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel);
  93. ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT);
  94. if (ret < 0)
  95. return ret;
  96. data->time_prev = ktime_get();
  97. return devm_iio_device_register(&client->dev, indio_dev);
  98. }
  99. static const struct i2c_device_id ltc2485_id[] = {
  100. { "ltc2485", 0 },
  101. { }
  102. };
  103. MODULE_DEVICE_TABLE(i2c, ltc2485_id);
  104. static struct i2c_driver ltc2485_driver = {
  105. .driver = {
  106. .name = "ltc2485",
  107. },
  108. .probe = ltc2485_probe,
  109. .id_table = ltc2485_id,
  110. };
  111. module_i2c_driver(ltc2485_driver);
  112. MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>");
  113. MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver");
  114. MODULE_LICENSE("GPL v2");