1 /* 2 * ltc2485.c - Driver for Linear Technology LTC2485 ADC 3 * 4 * Copyright (C) 2016 Alison Schofield <amsfield22@gmail.com> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * Datasheet: http://cds.linear.com/docs/en/datasheet/2485fd.pdf 11 */ 12 13 #include <linux/delay.h> 14 #include <linux/i2c.h> 15 #include <linux/module.h> 16 17 #include <linux/iio/iio.h> 18 #include <linux/iio/sysfs.h> 19 20 /* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */ 21 #define LTC2485_CONFIG_DEFAULT 0 22 23 struct ltc2485_data { 24 struct i2c_client *client; 25 ktime_t time_prev; /* last conversion */ 26 }; 27 28 static void ltc2485_wait_conv(struct ltc2485_data *data) 29 { 30 const unsigned int conv_time = 147; /* conversion time ms */ 31 unsigned int time_elapsed; 32 33 /* delay if conversion time not passed since last read or write */ 34 time_elapsed = ktime_ms_delta(ktime_get(), data->time_prev); 35 36 if (time_elapsed < conv_time) 37 msleep(conv_time - time_elapsed); 38 } 39 40 static int ltc2485_read(struct ltc2485_data *data, int *val) 41 { 42 struct i2c_client *client = data->client; 43 __be32 buf = 0; 44 int ret; 45 46 ltc2485_wait_conv(data); 47 48 ret = i2c_master_recv(client, (char *)&buf, 4); 49 if (ret < 0) { 50 dev_err(&client->dev, "i2c_master_recv failed\n"); 51 return ret; 52 } 53 data->time_prev = ktime_get(); 54 *val = sign_extend32(be32_to_cpu(buf) >> 6, 24); 55 56 return ret; 57 } 58 59 static int ltc2485_read_raw(struct iio_dev *indio_dev, 60 struct iio_chan_spec const *chan, 61 int *val, int *val2, long mask) 62 { 63 struct ltc2485_data *data = iio_priv(indio_dev); 64 int ret; 65 66 if (mask == IIO_CHAN_INFO_RAW) { 67 ret = ltc2485_read(data, val); 68 if (ret < 0) 69 return ret; 70 71 return IIO_VAL_INT; 72 73 } else if (mask == IIO_CHAN_INFO_SCALE) { 74 *val = 5000; /* on board vref millivolts */ 75 *val2 = 25; /* 25 (24 + sign) data bits */ 76 return IIO_VAL_FRACTIONAL_LOG2; 77 78 } else { 79 return -EINVAL; 80 } 81 } 82 83 static const struct iio_chan_spec ltc2485_channel[] = { 84 { 85 .type = IIO_VOLTAGE, 86 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 87 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) 88 }, 89 }; 90 91 static const struct iio_info ltc2485_info = { 92 .read_raw = ltc2485_read_raw, 93 .driver_module = THIS_MODULE, 94 }; 95 96 static int ltc2485_probe(struct i2c_client *client, 97 const struct i2c_device_id *id) 98 { 99 struct iio_dev *indio_dev; 100 struct ltc2485_data *data; 101 int ret; 102 103 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C | 104 I2C_FUNC_SMBUS_WRITE_BYTE)) 105 return -EOPNOTSUPP; 106 107 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); 108 if (!indio_dev) 109 return -ENOMEM; 110 111 data = iio_priv(indio_dev); 112 i2c_set_clientdata(client, indio_dev); 113 data->client = client; 114 115 indio_dev->dev.parent = &client->dev; 116 indio_dev->name = id->name; 117 indio_dev->info = <c2485_info; 118 indio_dev->modes = INDIO_DIRECT_MODE; 119 indio_dev->channels = ltc2485_channel; 120 indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel); 121 122 ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT); 123 if (ret < 0) 124 return ret; 125 126 data->time_prev = ktime_get(); 127 128 return devm_iio_device_register(&client->dev, indio_dev); 129 } 130 131 static const struct i2c_device_id ltc2485_id[] = { 132 { "ltc2485", 0 }, 133 { } 134 }; 135 MODULE_DEVICE_TABLE(i2c, ltc2485_id); 136 137 static struct i2c_driver ltc2485_driver = { 138 .driver = { 139 .name = "ltc2485", 140 }, 141 .probe = ltc2485_probe, 142 .id_table = ltc2485_id, 143 }; 144 module_i2c_driver(ltc2485_driver); 145 146 MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>"); 147 MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver"); 148 MODULE_LICENSE("GPL v2"); 149