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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 | ||
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 */ | |
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 | ||
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 | ||
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 | ||
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 | ||
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"); |