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
32struct 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
42struct am2315_sensor_data {
43	s16 hum_data;
44	s16 temp_data;
45};
46
47static 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). */
76static 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. */
97static void am2315_ping(struct i2c_client *client)
98{
99	i2c_smbus_read_byte_data(client, AM2315_REG_HUM_MSB);
100}
101
102static 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
152exit_unlock:
153	mutex_unlock(&data->lock);
154	return ret;
155}
156
157static 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);
188err:
189	iio_trigger_notify_done(indio_dev->trig);
190	return IRQ_HANDLED;
191}
192
193static 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
217static const struct iio_info am2315_info = {
218	.read_raw		= am2315_read_raw,
219};
220
221static int am2315_probe(struct i2c_client *client)
222{
223	int ret;
224	struct iio_dev *indio_dev;
225	struct am2315_data *data;
226
227	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
228	if (!indio_dev) {
229		dev_err(&client->dev, "iio allocation failed!\n");
230		return -ENOMEM;
231	}
232
233	data = iio_priv(indio_dev);
234	data->client = client;
235	i2c_set_clientdata(client, indio_dev);
236	mutex_init(&data->lock);
237
238	indio_dev->info = &am2315_info;
239	indio_dev->name = AM2315_DRIVER_NAME;
240	indio_dev->modes = INDIO_DIRECT_MODE;
241	indio_dev->channels = am2315_channels;
242	indio_dev->num_channels = ARRAY_SIZE(am2315_channels);
243
244	ret = devm_iio_triggered_buffer_setup(&client->dev,
245					indio_dev, iio_pollfunc_store_time,
246					 am2315_trigger_handler, NULL);
247	if (ret < 0) {
248		dev_err(&client->dev, "iio triggered buffer setup failed\n");
249		return ret;
250	}
251
252	return devm_iio_device_register(&client->dev, indio_dev);
253}
254
255static const struct i2c_device_id am2315_i2c_id[] = {
256	{"am2315", 0},
257	{}
258};
259MODULE_DEVICE_TABLE(i2c, am2315_i2c_id);
260
261static struct i2c_driver am2315_driver = {
262	.driver = {
263		.name = "am2315",
264	},
265	.probe =        am2315_probe,
266	.id_table =         am2315_i2c_id,
267};
268
269module_i2c_driver(am2315_driver);
270
271MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
272MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature");
273MODULE_LICENSE("GPL v2");
274