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 10 #include <linux/delay.h> 11 #include <linux/i2c.h> 12 #include <linux/module.h> 13 14 #include <linux/iio/iio.h> 15 #include <linux/iio/sysfs.h> 16 17 /* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */ 18 #define LTC2485_CONFIG_DEFAULT 0 19 20 struct ltc2485_data { 21 struct i2c_client *client; 22 ktime_t time_prev; /* last conversion */ 23 }; 24 25 static void ltc2485_wait_conv(struct ltc2485_data *data) 26 { 27 const unsigned int conv_time = 147; /* conversion time ms */ 28 unsigned int time_elapsed; 29 30 /* delay if conversion time not passed since last read or write */ 31 time_elapsed = ktime_ms_delta(ktime_get(), data->time_prev); 32 33 if (time_elapsed < conv_time) 34 msleep(conv_time - time_elapsed); 35 } 36 37 static int ltc2485_read(struct ltc2485_data *data, int *val) 38 { 39 struct i2c_client *client = data->client; 40 __be32 buf = 0; 41 int ret; 42 43 ltc2485_wait_conv(data); 44 45 ret = i2c_master_recv(client, (char *)&buf, 4); 46 if (ret < 0) { 47 dev_err(&client->dev, "i2c_master_recv failed\n"); 48 return ret; 49 } 50 data->time_prev = ktime_get(); 51 *val = sign_extend32(be32_to_cpu(buf) >> 6, 24); 52 53 return ret; 54 } 55 56 static int ltc2485_read_raw(struct iio_dev *indio_dev, 57 struct iio_chan_spec const *chan, 58 int *val, int *val2, long mask) 59 { 60 struct ltc2485_data *data = iio_priv(indio_dev); 61 int ret; 62 63 if (mask == IIO_CHAN_INFO_RAW) { 64 ret = ltc2485_read(data, val); 65 if (ret < 0) 66 return ret; 67 68 return IIO_VAL_INT; 69 70 } else if (mask == IIO_CHAN_INFO_SCALE) { 71 *val = 5000; /* on board vref millivolts */ 72 *val2 = 25; /* 25 (24 + sign) data bits */ 73 return IIO_VAL_FRACTIONAL_LOG2; 74 75 } else { 76 return -EINVAL; 77 } 78 } 79 80 static const struct iio_chan_spec ltc2485_channel[] = { 81 { 82 .type = IIO_VOLTAGE, 83 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), 84 .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) 85 }, 86 }; 87 88 static const struct iio_info ltc2485_info = { 89 .read_raw = ltc2485_read_raw, 90 }; 91 92 static int ltc2485_probe(struct i2c_client *client) 93 { 94 const struct i2c_device_id *id = i2c_client_get_device_id(client); 95 struct iio_dev *indio_dev; 96 struct ltc2485_data *data; 97 int ret; 98 99 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C | 100 I2C_FUNC_SMBUS_WRITE_BYTE)) 101 return -EOPNOTSUPP; 102 103 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); 104 if (!indio_dev) 105 return -ENOMEM; 106 107 data = iio_priv(indio_dev); 108 i2c_set_clientdata(client, indio_dev); 109 data->client = client; 110 111 indio_dev->name = id->name; 112 indio_dev->info = <c2485_info; 113 indio_dev->modes = INDIO_DIRECT_MODE; 114 indio_dev->channels = ltc2485_channel; 115 indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel); 116 117 ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT); 118 if (ret < 0) 119 return ret; 120 121 data->time_prev = ktime_get(); 122 123 return devm_iio_device_register(&client->dev, indio_dev); 124 } 125 126 static const struct i2c_device_id ltc2485_id[] = { 127 { "ltc2485", 0 }, 128 { } 129 }; 130 MODULE_DEVICE_TABLE(i2c, ltc2485_id); 131 132 static struct i2c_driver ltc2485_driver = { 133 .driver = { 134 .name = "ltc2485", 135 }, 136 .probe_new = ltc2485_probe, 137 .id_table = ltc2485_id, 138 }; 139 module_i2c_driver(ltc2485_driver); 140 141 MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>"); 142 MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver"); 143 MODULE_LICENSE("GPL v2"); 144