1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Aosong AM2315 relative humidity and temperature 4 * 5 * Copyright (c) 2016, Intel Corporation. 6 * 7 * 7-bit I2C address: 0x5C. 8 */ 9 10 #include <linux/delay.h> 11 #include <linux/i2c.h> 12 #include <linux/kernel.h> 13 #include <linux/module.h> 14 #include <linux/iio/buffer.h> 15 #include <linux/iio/iio.h> 16 #include <linux/iio/sysfs.h> 17 #include <linux/iio/trigger_consumer.h> 18 #include <linux/iio/triggered_buffer.h> 19 20 #define AM2315_REG_HUM_MSB 0x00 21 #define AM2315_REG_HUM_LSB 0x01 22 #define AM2315_REG_TEMP_MSB 0x02 23 #define AM2315_REG_TEMP_LSB 0x03 24 25 #define AM2315_FUNCTION_READ 0x03 26 #define AM2315_HUM_OFFSET 2 27 #define AM2315_TEMP_OFFSET 4 28 #define AM2315_ALL_CHANNEL_MASK GENMASK(1, 0) 29 30 #define AM2315_DRIVER_NAME "am2315" 31 32 struct am2315_data { 33 struct i2c_client *client; 34 struct mutex lock; 35 /* Ensure timestamp is naturally aligned */ 36 struct { 37 s16 chans[2]; 38 s64 timestamp __aligned(8); 39 } scan; 40 }; 41 42 struct am2315_sensor_data { 43 s16 hum_data; 44 s16 temp_data; 45 }; 46 47 static const struct iio_chan_spec am2315_channels[] = { 48 { 49 .type = IIO_HUMIDITYRELATIVE, 50 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 51 BIT(IIO_CHAN_INFO_SCALE), 52 .scan_index = 0, 53 .scan_type = { 54 .sign = 's', 55 .realbits = 16, 56 .storagebits = 16, 57 .endianness = IIO_CPU, 58 }, 59 }, 60 { 61 .type = IIO_TEMP, 62 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 63 BIT(IIO_CHAN_INFO_SCALE), 64 .scan_index = 1, 65 .scan_type = { 66 .sign = 's', 67 .realbits = 16, 68 .storagebits = 16, 69 .endianness = IIO_CPU, 70 }, 71 }, 72 IIO_CHAN_SOFT_TIMESTAMP(2), 73 }; 74 75 /* CRC calculation algorithm, as specified in the datasheet (page 13). */ 76 static u16 am2315_crc(u8 *data, u8 nr_bytes) 77 { 78 int i; 79 u16 crc = 0xffff; 80 81 while (nr_bytes--) { 82 crc ^= *data++; 83 for (i = 0; i < 8; i++) { 84 if (crc & 0x01) { 85 crc >>= 1; 86 crc ^= 0xA001; 87 } else { 88 crc >>= 1; 89 } 90 } 91 } 92 93 return crc; 94 } 95 96 /* Simple function that sends a few bytes to the device to wake it up. */ 97 static void am2315_ping(struct i2c_client *client) 98 { 99 i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB); 100 } 101 102 static int am2315_read_data(struct am2315_data *data, 103 struct am2315_sensor_data *sensor_data) 104 { 105 int ret; 106 /* tx_buf format: <function code> <start addr> <nr of regs to read> */ 107 u8 tx_buf[3] = { AM2315_FUNCTION_READ, AM2315_REG_HUM_MSB, 4 }; 108 /* 109 * rx_buf format: 110 * <function code> <number of registers read> 111 * <humidity MSB> <humidity LSB> <temp MSB> <temp LSB> 112 * <CRC LSB> <CRC MSB> 113 */ 114 u8 rx_buf[8]; 115 u16 crc; 116 117 /* First wake up the device. */ 118 am2315_ping(data->client); 119 120 mutex_lock(&data->lock); 121 ret = i2c_master_send(data->client, tx_buf, sizeof(tx_buf)); 122 if (ret < 0) { 123 dev_err(&data->client->dev, "failed to send read request\n"); 124 goto exit_unlock; 125 } 126 /* Wait 2-3 ms, then read back the data sent by the device. */ 127 usleep_range(2000, 3000); 128 /* Do a bulk data read, then pick out what we need. */ 129 ret = i2c_master_recv(data->client, rx_buf, sizeof(rx_buf)); 130 if (ret < 0) { 131 dev_err(&data->client->dev, "failed to read sensor data\n"); 132 goto exit_unlock; 133 } 134 mutex_unlock(&data->lock); 135 /* 136 * Do a CRC check on the data and compare it to the value 137 * calculated by the device. 138 */ 139 crc = am2315_crc(rx_buf, sizeof(rx_buf) - 2); 140 if ((crc & 0xff) != rx_buf[6] || (crc >> 8) != rx_buf[7]) { 141 dev_err(&data->client->dev, "failed to verify sensor data\n"); 142 return -EIO; 143 } 144 145 sensor_data->hum_data = (rx_buf[AM2315_HUM_OFFSET] << 8) | 146 rx_buf[AM2315_HUM_OFFSET + 1]; 147 sensor_data->temp_data = (rx_buf[AM2315_TEMP_OFFSET] << 8) | 148 rx_buf[AM2315_TEMP_OFFSET + 1]; 149 150 return ret; 151 152 exit_unlock: 153 mutex_unlock(&data->lock); 154 return ret; 155 } 156 157 static irqreturn_t am2315_trigger_handler(int irq, void *p) 158 { 159 int i; 160 int ret; 161 int bit; 162 struct iio_poll_func *pf = p; 163 struct iio_dev *indio_dev = pf->indio_dev; 164 struct am2315_data *data = iio_priv(indio_dev); 165 struct am2315_sensor_data sensor_data; 166 167 ret = am2315_read_data(data, &sensor_data); 168 if (ret < 0) 169 goto err; 170 171 mutex_lock(&data->lock); 172 if (*(indio_dev->active_scan_mask) == AM2315_ALL_CHANNEL_MASK) { 173 data->scan.chans[0] = sensor_data.hum_data; 174 data->scan.chans[1] = sensor_data.temp_data; 175 } else { 176 i = 0; 177 for_each_set_bit(bit, indio_dev->active_scan_mask, 178 indio_dev->masklength) { 179 data->scan.chans[i] = (bit ? sensor_data.temp_data : 180 sensor_data.hum_data); 181 i++; 182 } 183 } 184 mutex_unlock(&data->lock); 185 186 iio_push_to_buffers_with_timestamp(indio_dev, &data->scan, 187 pf->timestamp); 188 err: 189 iio_trigger_notify_done(indio_dev->trig); 190 return IRQ_HANDLED; 191 } 192 193 static int am2315_read_raw(struct iio_dev *indio_dev, 194 struct iio_chan_spec const *chan, 195 int *val, int *val2, long mask) 196 { 197 int ret; 198 struct am2315_sensor_data sensor_data; 199 struct am2315_data *data = iio_priv(indio_dev); 200 201 switch (mask) { 202 case IIO_CHAN_INFO_RAW: 203 ret = am2315_read_data(data, &sensor_data); 204 if (ret < 0) 205 return ret; 206 *val = (chan->type == IIO_HUMIDITYRELATIVE) ? 207 sensor_data.hum_data : sensor_data.temp_data; 208 return IIO_VAL_INT; 209 case IIO_CHAN_INFO_SCALE: 210 *val = 100; 211 return IIO_VAL_INT; 212 } 213 214 return -EINVAL; 215 } 216 217 static const struct iio_info am2315_info = { 218 .read_raw = am2315_read_raw, 219 }; 220 221 static int am2315_probe(struct i2c_client *client, 222 const struct i2c_device_id *id) 223 { 224 int ret; 225 struct iio_dev *indio_dev; 226 struct am2315_data *data; 227 228 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); 229 if (!indio_dev) { 230 dev_err(&client->dev, "iio allocation failed!\n"); 231 return -ENOMEM; 232 } 233 234 data = iio_priv(indio_dev); 235 data->client = client; 236 i2c_set_clientdata(client, indio_dev); 237 mutex_init(&data->lock); 238 239 indio_dev->info = &am2315_info; 240 indio_dev->name = AM2315_DRIVER_NAME; 241 indio_dev->modes = INDIO_DIRECT_MODE; 242 indio_dev->channels = am2315_channels; 243 indio_dev->num_channels = ARRAY_SIZE(am2315_channels); 244 245 ret = devm_iio_triggered_buffer_setup(&client->dev, 246 indio_dev, iio_pollfunc_store_time, 247 am2315_trigger_handler, NULL); 248 if (ret < 0) { 249 dev_err(&client->dev, "iio triggered buffer setup failed\n"); 250 return ret; 251 } 252 253 return devm_iio_device_register(&client->dev, indio_dev); 254 } 255 256 static const struct i2c_device_id am2315_i2c_id[] = { 257 {"am2315", 0}, 258 {} 259 }; 260 MODULE_DEVICE_TABLE(i2c, am2315_i2c_id); 261 262 static struct i2c_driver am2315_driver = { 263 .driver = { 264 .name = "am2315", 265 }, 266 .probe = am2315_probe, 267 .id_table = am2315_i2c_id, 268 }; 269 270 module_i2c_driver(am2315_driver); 271 272 MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>"); 273 MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature"); 274 MODULE_LICENSE("GPL v2"); 275