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) */
29 static const unsigned char shtc1_cmd_measure_blocking_hpm[] = { 0x7C, 0xA2 };
30 static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
31
32 /* commands (low precision mode) */
33 static const unsigned char shtc1_cmd_measure_blocking_lpm[] = { 0x64, 0x58 };
34 static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
35
36 /* command for reading the ID register */
37 static 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
50 struct 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
shtc1_update_values(struct i2c_client * client,struct shtc1_data * data,char * buf,int bufsize)65 static 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 */
shtc1_update_client(struct device * dev)95 static 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
126 out:
127 mutex_unlock(&data->update_lock);
128
129 return ret == 0 ? data : ERR_PTR(ret);
130 }
131
temp1_input_show(struct device * dev,struct device_attribute * attr,char * buf)132 static 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
humidity1_input_show(struct device * dev,struct device_attribute * attr,char * buf)143 static 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
153 static DEVICE_ATTR_RO(temp1_input);
154 static DEVICE_ATTR_RO(humidity1_input);
155
156 static struct attribute *shtc1_attrs[] = {
157 &dev_attr_temp1_input.attr,
158 &dev_attr_humidity1_input.attr,
159 NULL
160 };
161
162 ATTRIBUTE_GROUPS(shtc1);
163
shtc1_select_command(struct shtc1_data * data)164 static 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
shtc1_probe(struct i2c_client * client,const struct i2c_device_id * id)180 static 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 */
234 static const struct i2c_device_id shtc1_id[] = {
235 { "shtc1", 0 },
236 { "shtw1", 0 },
237 { }
238 };
239 MODULE_DEVICE_TABLE(i2c, shtc1_id);
240
241 static struct i2c_driver shtc1_i2c_driver = {
242 .driver.name = "shtc1",
243 .probe = shtc1_probe,
244 .id_table = shtc1_id,
245 };
246
247 module_i2c_driver(shtc1_i2c_driver);
248
249 MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
250 MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
251 MODULE_LICENSE("GPL");
252