1/* Sensirion SHTC1 humidity and temperature sensor driver
2 *
3 * Copyright (C) 2014 Sensirion AG, Switzerland
4 * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 */
17
18#include <linux/module.h>
19#include <linux/init.h>
20#include <linux/slab.h>
21#include <linux/i2c.h>
22#include <linux/hwmon.h>
23#include <linux/hwmon-sysfs.h>
24#include <linux/err.h>
25#include <linux/delay.h>
26#include <linux/platform_data/shtc1.h>
27
28/* commands (high precision mode) */
29static const unsigned char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
30static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
31
32/* commands (low precision mode) */
33static const unsigned char shtc1_cmd_measure_blocking_lpm[]    = { 0x64, 0x58 };
34static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
35
36/* command for reading the ID register */
37static const unsigned char shtc1_cmd_read_id_reg[]	       = { 0xef, 0xc8 };
38
39/* constants for reading the ID register */
40#define SHTC1_ID	  0x07
41#define SHTC1_ID_REG_MASK 0x1f
42
43/* delays for non-blocking i2c commands, both in us */
44#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  14400
45#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1000
46
47#define SHTC1_CMD_LENGTH      2
48#define SHTC1_RESPONSE_LENGTH 6
49
50struct shtc1_data {
51	struct i2c_client *client;
52	struct mutex update_lock;
53	bool valid;
54	unsigned long last_updated; /* in jiffies */
55
56	const unsigned char *command;
57	unsigned int nonblocking_wait_time; /* in us */
58
59	struct shtc1_platform_data setup;
60
61	int temperature; /* 1000 * temperature in dgr C */
62	int humidity; /* 1000 * relative humidity in %RH */
63};
64
65static int shtc1_update_values(struct i2c_client *client,
66			       struct shtc1_data *data,
67			       char *buf, int bufsize)
68{
69	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
70	if (ret != SHTC1_CMD_LENGTH) {
71		dev_err(&client->dev, "failed to send command: %d\n", ret);
72		return ret < 0 ? ret : -EIO;
73	}
74
75	/*
76	 * In blocking mode (clock stretching mode) the I2C bus
77	 * is blocked for other traffic, thus the call to i2c_master_recv()
78	 * will wait until the data is ready. For non blocking mode, we
79	 * have to wait ourselves.
80	 */
81	if (!data->setup.blocking_io)
82		usleep_range(data->nonblocking_wait_time,
83			     data->nonblocking_wait_time + 1000);
84
85	ret = i2c_master_recv(client, buf, bufsize);
86	if (ret != bufsize) {
87		dev_err(&client->dev, "failed to read values: %d\n", ret);
88		return ret < 0 ? ret : -EIO;
89	}
90
91	return 0;
92}
93
94/* sysfs attributes */
95static struct shtc1_data *shtc1_update_client(struct device *dev)
96{
97	struct shtc1_data *data = dev_get_drvdata(dev);
98	struct i2c_client *client = data->client;
99	unsigned char buf[SHTC1_RESPONSE_LENGTH];
100	int val;
101	int ret = 0;
102
103	mutex_lock(&data->update_lock);
104
105	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
106		ret = shtc1_update_values(client, data, buf, sizeof(buf));
107		if (ret)
108			goto out;
109
110		/*
111		 * From datasheet:
112		 * T = -45 + 175 * ST / 2^16
113		 * RH = 100 * SRH / 2^16
114		 *
115		 * Adapted for integer fixed point (3 digit) arithmetic.
116		 */
117		val = be16_to_cpup((__be16 *)buf);
118		data->temperature = ((21875 * val) >> 13) - 45000;
119		val = be16_to_cpup((__be16 *)(buf + 3));
120		data->humidity = ((12500 * val) >> 13);
121
122		data->last_updated = jiffies;
123		data->valid = true;
124	}
125
126out:
127	mutex_unlock(&data->update_lock);
128
129	return ret == 0 ? data : ERR_PTR(ret);
130}
131
132static ssize_t temp1_input_show(struct device *dev,
133				struct device_attribute *attr,
134				char *buf)
135{
136	struct shtc1_data *data = shtc1_update_client(dev);
137	if (IS_ERR(data))
138		return PTR_ERR(data);
139
140	return sprintf(buf, "%d\n", data->temperature);
141}
142
143static ssize_t humidity1_input_show(struct device *dev,
144				    struct device_attribute *attr, char *buf)
145{
146	struct shtc1_data *data = shtc1_update_client(dev);
147	if (IS_ERR(data))
148		return PTR_ERR(data);
149
150	return sprintf(buf, "%d\n", data->humidity);
151}
152
153static DEVICE_ATTR_RO(temp1_input);
154static DEVICE_ATTR_RO(humidity1_input);
155
156static struct attribute *shtc1_attrs[] = {
157	&dev_attr_temp1_input.attr,
158	&dev_attr_humidity1_input.attr,
159	NULL
160};
161
162ATTRIBUTE_GROUPS(shtc1);
163
164static void shtc1_select_command(struct shtc1_data *data)
165{
166	if (data->setup.high_precision) {
167		data->command = data->setup.blocking_io ?
168				shtc1_cmd_measure_blocking_hpm :
169				shtc1_cmd_measure_nonblocking_hpm;
170		data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM;
171
172	} else {
173		data->command = data->setup.blocking_io ?
174				shtc1_cmd_measure_blocking_lpm :
175				shtc1_cmd_measure_nonblocking_lpm;
176		data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM;
177	}
178}
179
180static int shtc1_probe(struct i2c_client *client,
181		       const struct i2c_device_id *id)
182{
183	int ret;
184	char id_reg[2];
185	struct shtc1_data *data;
186	struct device *hwmon_dev;
187	struct i2c_adapter *adap = client->adapter;
188	struct device *dev = &client->dev;
189
190	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
191		dev_err(dev, "plain i2c transactions not supported\n");
192		return -ENODEV;
193	}
194
195	ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
196	if (ret != SHTC1_CMD_LENGTH) {
197		dev_err(dev, "could not send read_id_reg command: %d\n", ret);
198		return ret < 0 ? ret : -ENODEV;
199	}
200	ret = i2c_master_recv(client, id_reg, sizeof(id_reg));
201	if (ret != sizeof(id_reg)) {
202		dev_err(dev, "could not read ID register: %d\n", ret);
203		return -ENODEV;
204	}
205	if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) {
206		dev_err(dev, "ID register doesn't match\n");
207		return -ENODEV;
208	}
209
210	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
211	if (!data)
212		return -ENOMEM;
213
214	data->setup.blocking_io = false;
215	data->setup.high_precision = true;
216	data->client = client;
217
218	if (client->dev.platform_data)
219		data->setup = *(struct shtc1_platform_data *)dev->platform_data;
220	shtc1_select_command(data);
221	mutex_init(&data->update_lock);
222
223	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
224							   client->name,
225							   data,
226							   shtc1_groups);
227	if (IS_ERR(hwmon_dev))
228		dev_dbg(dev, "unable to register hwmon device\n");
229
230	return PTR_ERR_OR_ZERO(hwmon_dev);
231}
232
233/* device ID table */
234static const struct i2c_device_id shtc1_id[] = {
235	{ "shtc1", 0 },
236	{ "shtw1", 0 },
237	{ }
238};
239MODULE_DEVICE_TABLE(i2c, shtc1_id);
240
241static struct i2c_driver shtc1_i2c_driver = {
242	.driver.name  = "shtc1",
243	.probe        = shtc1_probe,
244	.id_table     = shtc1_id,
245};
246
247module_i2c_driver(shtc1_i2c_driver);
248
249MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
250MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
251MODULE_LICENSE("GPL");
252