am2315.c

  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		aligned_s64 timestamp;
 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		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);
187err:
188	iio_trigger_notify_done(indio_dev->trig);
189	return IRQ_HANDLED;
190}
191
192static 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
216static const struct iio_info am2315_info = {
217	.read_raw		= am2315_read_raw,
218};
219
220static 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		return -ENOMEM;
229
230	data = iio_priv(indio_dev);
231	data->client = client;
232	i2c_set_clientdata(client, indio_dev);
233	mutex_init(&data->lock);
234
235	indio_dev->info = &am2315_info;
236	indio_dev->name = AM2315_DRIVER_NAME;
237	indio_dev->modes = INDIO_DIRECT_MODE;
238	indio_dev->channels = am2315_channels;
239	indio_dev->num_channels = ARRAY_SIZE(am2315_channels);
240
241	ret = devm_iio_triggered_buffer_setup(&client->dev,
242					indio_dev, iio_pollfunc_store_time,
243					 am2315_trigger_handler, NULL);
244	if (ret < 0) {
245		dev_err(&client->dev, "iio triggered buffer setup failed\n");
246		return ret;
247	}
248
249	return devm_iio_device_register(&client->dev, indio_dev);
250}
251
252static const struct i2c_device_id am2315_i2c_id[] = {
253	{ "am2315" },
254	{ }
255};
256MODULE_DEVICE_TABLE(i2c, am2315_i2c_id);
257
258static struct i2c_driver am2315_driver = {
259	.driver = {
260		.name = "am2315",
261	},
262	.probe =        am2315_probe,
263	.id_table =         am2315_i2c_id,
264};
265
266module_i2c_driver(am2315_driver);
267
268MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
269MODULE_DESCRIPTION("Aosong AM2315 relative humidity and temperature");
270MODULE_LICENSE("GPL v2");