1 // SPDX-License-Identifier: GPL-2.0-only
3 * Aosong AM2315 relative humidity and temperature
5 * Copyright (c) 2016, Intel Corporation.
7 * 7-bit I2C address: 0x5C.
10 #include <linux/acpi.h>
11 #include <linux/delay.h>
12 #include <linux/i2c.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/iio/buffer.h>
16 #include <linux/iio/iio.h>
17 #include <linux/iio/sysfs.h>
18 #include <linux/iio/trigger_consumer.h>
19 #include <linux/iio/triggered_buffer.h>
21 #define AM2315_REG_HUM_MSB 0x00
22 #define AM2315_REG_HUM_LSB 0x01
23 #define AM2315_REG_TEMP_MSB 0x02
24 #define AM2315_REG_TEMP_LSB 0x03
26 #define AM2315_FUNCTION_READ 0x03
27 #define AM2315_HUM_OFFSET 2
28 #define AM2315_TEMP_OFFSET 4
29 #define AM2315_ALL_CHANNEL_MASK GENMASK(1, 0)
31 #define AM2315_DRIVER_NAME "am2315"
34 struct i2c_client *client;
36 /* Ensure timestamp is naturally aligned */
39 s64 timestamp __aligned(8);
43 struct am2315_sensor_data {
48 static const struct iio_chan_spec am2315_channels[] = {
50 .type = IIO_HUMIDITYRELATIVE,
51 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
52 BIT(IIO_CHAN_INFO_SCALE),
58 .endianness = IIO_CPU,
63 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
64 BIT(IIO_CHAN_INFO_SCALE),
70 .endianness = IIO_CPU,
73 IIO_CHAN_SOFT_TIMESTAMP(2),
76 /* CRC calculation algorithm, as specified in the datasheet (page 13). */
77 static u16 am2315_crc(u8 *data, u8 nr_bytes)
84 for (i = 0; i < 8; i++) {
97 /* Simple function that sends a few bytes to the device to wake it up. */
98 static void am2315_ping(struct i2c_client *client)
100 i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB);
103 static int am2315_read_data(struct am2315_data *data,
104 struct am2315_sensor_data *sensor_data)
107 /* tx_buf format: <function code> <start addr> <nr of regs to read> */
108 u8 tx_buf[3] = { AM2315_FUNCTION_READ, AM2315_REG_HUM_MSB, 4 };
111 * <function code> <number of registers read>
112 * <humidity MSB> <humidity LSB> <temp MSB> <temp LSB>
113 * <CRC LSB> <CRC MSB>
118 /* First wake up the device. */
119 am2315_ping(data->client);
121 mutex_lock(&data->lock);
122 ret = i2c_master_send(data->client, tx_buf, sizeof(tx_buf));
124 dev_err(&data->client->dev, "failed to send read request\n");
127 /* Wait 2-3 ms, then read back the data sent by the device. */
128 usleep_range(2000, 3000);
129 /* Do a bulk data read, then pick out what we need. */
130 ret = i2c_master_recv(data->client, rx_buf, sizeof(rx_buf));
132 dev_err(&data->client->dev, "failed to read sensor data\n");
135 mutex_unlock(&data->lock);
137 * Do a CRC check on the data and compare it to the value
138 * calculated by the device.
140 crc = am2315_crc(rx_buf, sizeof(rx_buf) - 2);
141 if ((crc & 0xff) != rx_buf[6] || (crc >> 8) != rx_buf[7]) {
142 dev_err(&data->client->dev, "failed to verify sensor data\n");
146 sensor_data->hum_data = (rx_buf[AM2315_HUM_OFFSET] << 8) |
147 rx_buf[AM2315_HUM_OFFSET + 1];
148 sensor_data->temp_data = (rx_buf[AM2315_TEMP_OFFSET] << 8) |
149 rx_buf[AM2315_TEMP_OFFSET + 1];
154 mutex_unlock(&data->lock);
158 static irqreturn_t am2315_trigger_handler(int irq, void *p)
163 struct iio_poll_func *pf = p;
164 struct iio_dev *indio_dev = pf->indio_dev;
165 struct am2315_data *data = iio_priv(indio_dev);
166 struct am2315_sensor_data sensor_data;
168 ret = am2315_read_data(data, &sensor_data);
172 mutex_lock(&data->lock);
173 if (*(indio_dev->active_scan_mask) == AM2315_ALL_CHANNEL_MASK) {
174 data->scan.chans[0] = sensor_data.hum_data;
175 data->scan.chans[1] = sensor_data.temp_data;
178 for_each_set_bit(bit, indio_dev->active_scan_mask,
179 indio_dev->masklength) {
180 data->scan.chans[i] = (bit ? sensor_data.temp_data :
181 sensor_data.hum_data);
185 mutex_unlock(&data->lock);
187 iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
190 iio_trigger_notify_done(indio_dev->trig);
194 static int am2315_read_raw(struct iio_dev *indio_dev,
195 struct iio_chan_spec const *chan,
196 int *val, int *val2, long mask)
199 struct am2315_sensor_data sensor_data;
200 struct am2315_data *data = iio_priv(indio_dev);
203 case IIO_CHAN_INFO_RAW:
204 ret = am2315_read_data(data, &sensor_data);
207 *val = (chan->type == IIO_HUMIDITYRELATIVE) ?
208 sensor_data.hum_data : sensor_data.temp_data;
210 case IIO_CHAN_INFO_SCALE:
218 static const struct iio_info am2315_info = {
219 .read_raw = am2315_read_raw,
222 static int am2315_probe(struct i2c_client *client,
223 const struct i2c_device_id *id)
226 struct iio_dev *indio_dev;
227 struct am2315_data *data;
229 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
231 dev_err(&client->dev, "iio allocation failed!\n");
235 data = iio_priv(indio_dev);
236 data->client = client;
237 i2c_set_clientdata(client, indio_dev);
238 mutex_init(&data->lock);
240 indio_dev->info = &am2315_info;
241 indio_dev->name = AM2315_DRIVER_NAME;
242 indio_dev->modes = INDIO_DIRECT_MODE;
243 indio_dev->channels = am2315_channels;
244 indio_dev->num_channels = ARRAY_SIZE(am2315_channels);
246 ret = devm_iio_triggered_buffer_setup(&client->dev,
247 indio_dev, iio_pollfunc_store_time,
248 am2315_trigger_handler, NULL);
250 dev_err(&client->dev, "iio triggered buffer setup failed\n");
254 return devm_iio_device_register(&client->dev, indio_dev);
257 static const struct i2c_device_id am2315_i2c_id[] = {
261 MODULE_DEVICE_TABLE(i2c, am2315_i2c_id);
263 static const struct acpi_device_id am2315_acpi_id[] = {
268 MODULE_DEVICE_TABLE(acpi, am2315_acpi_id);
270 static struct i2c_driver am2315_driver = {
273 .acpi_match_table = ACPI_PTR(am2315_acpi_id),
275 .probe = am2315_probe,
276 .id_table = am2315_i2c_id,
279 module_i2c_driver(am2315_driver);
281 MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
282 MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature");
283 MODULE_LICENSE("GPL v2");