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). */
am2315_crc(u8 * data,u8 nr_bytes)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. */
am2315_ping(struct i2c_client * client)97 static void am2315_ping(struct i2c_client *client)
98 {
99 i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB);
100 }
101
am2315_read_data(struct am2315_data * data,struct am2315_sensor_data * sensor_data)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
am2315_trigger_handler(int irq,void * p)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 iio_for_each_active_channel(indio_dev, bit) {
178 data->scan.chans[i] = (bit ? sensor_data.temp_data :
179 sensor_data.hum_data);
180 i++;
181 }
182 }
183 mutex_unlock(&data->lock);
184
185 iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
186 pf->timestamp);
187 err:
188 iio_trigger_notify_done(indio_dev->trig);
189 return IRQ_HANDLED;
190 }
191
am2315_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)192 static int am2315_read_raw(struct iio_dev *indio_dev,
193 struct iio_chan_spec const *chan,
194 int *val, int *val2, long mask)
195 {
196 int ret;
197 struct am2315_sensor_data sensor_data;
198 struct am2315_data *data = iio_priv(indio_dev);
199
200 switch (mask) {
201 case IIO_CHAN_INFO_RAW:
202 ret = am2315_read_data(data, &sensor_data);
203 if (ret < 0)
204 return ret;
205 *val = (chan->type == IIO_HUMIDITYRELATIVE) ?
206 sensor_data.hum_data : sensor_data.temp_data;
207 return IIO_VAL_INT;
208 case IIO_CHAN_INFO_SCALE:
209 *val = 100;
210 return IIO_VAL_INT;
211 }
212
213 return -EINVAL;
214 }
215
216 static const struct iio_info am2315_info = {
217 .read_raw = am2315_read_raw,
218 };
219
am2315_probe(struct i2c_client * client)220 static int am2315_probe(struct i2c_client *client)
221 {
222 int ret;
223 struct iio_dev *indio_dev;
224 struct am2315_data *data;
225
226 indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
227 if (!indio_dev) {
228 dev_err(&client->dev, "iio allocation failed!\n");
229 return -ENOMEM;
230 }
231
232 data = iio_priv(indio_dev);
233 data->client = client;
234 i2c_set_clientdata(client, indio_dev);
235 mutex_init(&data->lock);
236
237 indio_dev->info = &am2315_info;
238 indio_dev->name = AM2315_DRIVER_NAME;
239 indio_dev->modes = INDIO_DIRECT_MODE;
240 indio_dev->channels = am2315_channels;
241 indio_dev->num_channels = ARRAY_SIZE(am2315_channels);
242
243 ret = devm_iio_triggered_buffer_setup(&client->dev,
244 indio_dev, iio_pollfunc_store_time,
245 am2315_trigger_handler, NULL);
246 if (ret < 0) {
247 dev_err(&client->dev, "iio triggered buffer setup failed\n");
248 return ret;
249 }
250
251 return devm_iio_device_register(&client->dev, indio_dev);
252 }
253
254 static const struct i2c_device_id am2315_i2c_id[] = {
255 { "am2315" },
256 {}
257 };
258 MODULE_DEVICE_TABLE(i2c, am2315_i2c_id);
259
260 static struct i2c_driver am2315_driver = {
261 .driver = {
262 .name = "am2315",
263 },
264 .probe = am2315_probe,
265 .id_table = am2315_i2c_id,
266 };
267
268 module_i2c_driver(am2315_driver);
269
270 MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
271 MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature");
272 MODULE_LICENSE("GPL v2");
273