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 		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 
am2315_read_raw(struct iio_dev * indio_dev,struct iio_chan_spec const * chan,int * val,int * val2,long mask)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 
am2315_probe(struct i2c_client * client,const struct i2c_device_id * id)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