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fd534e9b | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
430400b8 UF |
2 | /* Sensirion SHT21 humidity and temperature sensor driver |
3 | * | |
4 | * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com> | |
5 | * | |
ad736c1a | 6 | * Data sheet available at https://www.sensirion.com/file/datasheet_sht21 |
430400b8 UF |
7 | */ |
8 | ||
9 | #include <linux/module.h> | |
10 | #include <linux/init.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/i2c.h> | |
13 | #include <linux/hwmon.h> | |
14 | #include <linux/hwmon-sysfs.h> | |
15 | #include <linux/err.h> | |
16 | #include <linux/mutex.h> | |
17 | #include <linux/device.h> | |
dcd8f392 | 18 | #include <linux/jiffies.h> |
430400b8 UF |
19 | |
20 | /* I2C command bytes */ | |
21 | #define SHT21_TRIG_T_MEASUREMENT_HM 0xe3 | |
22 | #define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5 | |
53e678d7 PB |
23 | #define SHT21_READ_SNB_CMD1 0xFA |
24 | #define SHT21_READ_SNB_CMD2 0x0F | |
25 | #define SHT21_READ_SNAC_CMD1 0xFC | |
26 | #define SHT21_READ_SNAC_CMD2 0xC9 | |
430400b8 UF |
27 | |
28 | /** | |
29 | * struct sht21 - SHT21 device specific data | |
679f50b8 | 30 | * @client: I2C client device |
430400b8 | 31 | * @lock: mutex to protect measurement values |
430400b8 UF |
32 | * @last_update: time of last update (jiffies) |
33 | * @temperature: cached temperature measurement value | |
34 | * @humidity: cached humidity measurement value | |
53e678d7 PB |
35 | * @valid: only 0 before first measurement is taken |
36 | * @eic: cached electronic identification code text | |
430400b8 UF |
37 | */ |
38 | struct sht21 { | |
b8d56898 | 39 | struct i2c_client *client; |
430400b8 | 40 | struct mutex lock; |
430400b8 UF |
41 | unsigned long last_update; |
42 | int temperature; | |
43 | int humidity; | |
952a11ca | 44 | bool valid; |
53e678d7 | 45 | char eic[18]; |
430400b8 UF |
46 | }; |
47 | ||
48 | /** | |
49 | * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to | |
50 | * milli celsius | |
51 | * @ticks: temperature ticks value received from sensor | |
52 | */ | |
53 | static inline int sht21_temp_ticks_to_millicelsius(int ticks) | |
54 | { | |
55 | ticks &= ~0x0003; /* clear status bits */ | |
56 | /* | |
57 | * Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2, | |
58 | * optimized for integer fixed point (3 digits) arithmetic | |
59 | */ | |
60 | return ((21965 * ticks) >> 13) - 46850; | |
61 | } | |
62 | ||
63 | /** | |
64 | * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to | |
65 | * one-thousandths of a percent relative humidity | |
66 | * @ticks: humidity ticks value received from sensor | |
67 | */ | |
68 | static inline int sht21_rh_ticks_to_per_cent_mille(int ticks) | |
69 | { | |
70 | ticks &= ~0x0003; /* clear status bits */ | |
71 | /* | |
72 | * Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1, | |
73 | * optimized for integer fixed point (3 digits) arithmetic | |
74 | */ | |
75 | return ((15625 * ticks) >> 13) - 6000; | |
76 | } | |
77 | ||
430400b8 UF |
78 | /** |
79 | * sht21_update_measurements() - get updated measurements from device | |
b8d56898 | 80 | * @dev: device |
430400b8 UF |
81 | * |
82 | * Returns 0 on success, else negative errno. | |
83 | */ | |
b8d56898 | 84 | static int sht21_update_measurements(struct device *dev) |
430400b8 UF |
85 | { |
86 | int ret = 0; | |
b8d56898 AL |
87 | struct sht21 *sht21 = dev_get_drvdata(dev); |
88 | struct i2c_client *client = sht21->client; | |
430400b8 UF |
89 | |
90 | mutex_lock(&sht21->lock); | |
91 | /* | |
92 | * Data sheet 2.4: | |
93 | * SHT2x should not be active for more than 10% of the time - e.g. | |
94 | * maximum two measurements per second at 12bit accuracy shall be made. | |
95 | */ | |
96 | if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) { | |
90f4102c JD |
97 | ret = i2c_smbus_read_word_swapped(client, |
98 | SHT21_TRIG_T_MEASUREMENT_HM); | |
430400b8 UF |
99 | if (ret < 0) |
100 | goto out; | |
101 | sht21->temperature = sht21_temp_ticks_to_millicelsius(ret); | |
90f4102c JD |
102 | ret = i2c_smbus_read_word_swapped(client, |
103 | SHT21_TRIG_RH_MEASUREMENT_HM); | |
430400b8 UF |
104 | if (ret < 0) |
105 | goto out; | |
106 | sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret); | |
107 | sht21->last_update = jiffies; | |
952a11ca | 108 | sht21->valid = true; |
430400b8 UF |
109 | } |
110 | out: | |
111 | mutex_unlock(&sht21->lock); | |
112 | ||
113 | return ret >= 0 ? 0 : ret; | |
114 | } | |
115 | ||
116 | /** | |
ffdb3ba0 | 117 | * sht21_temperature_show() - show temperature measurement value in sysfs |
430400b8 UF |
118 | * @dev: device |
119 | * @attr: device attribute | |
120 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
121 | * | |
122 | * Will be called on read access to temp1_input sysfs attribute. | |
123 | * Returns number of bytes written into buffer, negative errno on error. | |
124 | */ | |
5512eb06 GR |
125 | static ssize_t sht21_temperature_show(struct device *dev, |
126 | struct device_attribute *attr, | |
127 | char *buf) | |
430400b8 | 128 | { |
b8d56898 AL |
129 | struct sht21 *sht21 = dev_get_drvdata(dev); |
130 | int ret; | |
131 | ||
132 | ret = sht21_update_measurements(dev); | |
430400b8 UF |
133 | if (ret < 0) |
134 | return ret; | |
135 | return sprintf(buf, "%d\n", sht21->temperature); | |
136 | } | |
137 | ||
138 | /** | |
ffdb3ba0 | 139 | * sht21_humidity_show() - show humidity measurement value in sysfs |
430400b8 UF |
140 | * @dev: device |
141 | * @attr: device attribute | |
142 | * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to | |
143 | * | |
144 | * Will be called on read access to humidity1_input sysfs attribute. | |
145 | * Returns number of bytes written into buffer, negative errno on error. | |
146 | */ | |
5512eb06 GR |
147 | static ssize_t sht21_humidity_show(struct device *dev, |
148 | struct device_attribute *attr, char *buf) | |
430400b8 | 149 | { |
b8d56898 AL |
150 | struct sht21 *sht21 = dev_get_drvdata(dev); |
151 | int ret; | |
152 | ||
153 | ret = sht21_update_measurements(dev); | |
430400b8 UF |
154 | if (ret < 0) |
155 | return ret; | |
156 | return sprintf(buf, "%d\n", sht21->humidity); | |
157 | } | |
158 | ||
53e678d7 PB |
159 | static ssize_t eic_read(struct sht21 *sht21) |
160 | { | |
161 | struct i2c_client *client = sht21->client; | |
162 | u8 tx[2]; | |
163 | u8 rx[8]; | |
164 | u8 eic[8]; | |
165 | struct i2c_msg msgs[2] = { | |
166 | { | |
167 | .addr = client->addr, | |
168 | .flags = 0, | |
169 | .len = 2, | |
170 | .buf = tx, | |
171 | }, | |
172 | { | |
173 | .addr = client->addr, | |
174 | .flags = I2C_M_RD, | |
175 | .len = 8, | |
176 | .buf = rx, | |
177 | }, | |
178 | }; | |
179 | int ret; | |
180 | ||
181 | tx[0] = SHT21_READ_SNB_CMD1; | |
182 | tx[1] = SHT21_READ_SNB_CMD2; | |
183 | ret = i2c_transfer(client->adapter, msgs, 2); | |
184 | if (ret < 0) | |
185 | goto out; | |
186 | eic[2] = rx[0]; | |
187 | eic[3] = rx[2]; | |
188 | eic[4] = rx[4]; | |
189 | eic[5] = rx[6]; | |
190 | ||
191 | tx[0] = SHT21_READ_SNAC_CMD1; | |
192 | tx[1] = SHT21_READ_SNAC_CMD2; | |
193 | msgs[1].len = 6; | |
194 | ret = i2c_transfer(client->adapter, msgs, 2); | |
195 | if (ret < 0) | |
196 | goto out; | |
197 | eic[0] = rx[3]; | |
198 | eic[1] = rx[4]; | |
199 | eic[6] = rx[0]; | |
200 | eic[7] = rx[1]; | |
201 | ||
202 | ret = snprintf(sht21->eic, sizeof(sht21->eic), | |
203 | "%02x%02x%02x%02x%02x%02x%02x%02x\n", | |
204 | eic[0], eic[1], eic[2], eic[3], | |
205 | eic[4], eic[5], eic[6], eic[7]); | |
206 | out: | |
207 | if (ret < 0) | |
208 | sht21->eic[0] = 0; | |
209 | ||
210 | return ret; | |
211 | } | |
212 | ||
213 | /** | |
214 | * eic_show() - show Electronic Identification Code in sysfs | |
215 | * @dev: device | |
216 | * @attr: device attribute | |
217 | * @buf: sysfs buffer (PAGE_SIZE) where EIC is written | |
218 | * | |
219 | * Will be called on read access to eic sysfs attribute. | |
220 | * Returns number of bytes written into buffer, negative errno on error. | |
221 | */ | |
222 | static ssize_t eic_show(struct device *dev, | |
223 | struct device_attribute *attr, | |
224 | char *buf) | |
225 | { | |
226 | struct sht21 *sht21 = dev_get_drvdata(dev); | |
227 | int ret; | |
228 | ||
229 | ret = sizeof(sht21->eic) - 1; | |
230 | mutex_lock(&sht21->lock); | |
231 | if (!sht21->eic[0]) | |
232 | ret = eic_read(sht21); | |
233 | if (ret > 0) | |
234 | memcpy(buf, sht21->eic, ret); | |
235 | mutex_unlock(&sht21->lock); | |
236 | return ret; | |
237 | } | |
238 | ||
430400b8 | 239 | /* sysfs attributes */ |
5512eb06 GR |
240 | static SENSOR_DEVICE_ATTR_RO(temp1_input, sht21_temperature, 0); |
241 | static SENSOR_DEVICE_ATTR_RO(humidity1_input, sht21_humidity, 0); | |
53e678d7 | 242 | static DEVICE_ATTR_RO(eic); |
430400b8 | 243 | |
b8d56898 | 244 | static struct attribute *sht21_attrs[] = { |
430400b8 UF |
245 | &sensor_dev_attr_temp1_input.dev_attr.attr, |
246 | &sensor_dev_attr_humidity1_input.dev_attr.attr, | |
53e678d7 | 247 | &dev_attr_eic.attr, |
430400b8 UF |
248 | NULL |
249 | }; | |
250 | ||
b8d56898 | 251 | ATTRIBUTE_GROUPS(sht21); |
430400b8 | 252 | |
67487038 | 253 | static int sht21_probe(struct i2c_client *client) |
430400b8 | 254 | { |
b8d56898 AL |
255 | struct device *dev = &client->dev; |
256 | struct device *hwmon_dev; | |
430400b8 | 257 | struct sht21 *sht21; |
430400b8 UF |
258 | |
259 | if (!i2c_check_functionality(client->adapter, | |
260 | I2C_FUNC_SMBUS_WORD_DATA)) { | |
261 | dev_err(&client->dev, | |
262 | "adapter does not support SMBus word transactions\n"); | |
263 | return -ENODEV; | |
264 | } | |
265 | ||
b8d56898 | 266 | sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL); |
a844af19 | 267 | if (!sht21) |
430400b8 | 268 | return -ENOMEM; |
a844af19 | 269 | |
b8d56898 | 270 | sht21->client = client; |
430400b8 UF |
271 | |
272 | mutex_init(&sht21->lock); | |
273 | ||
b8d56898 AL |
274 | hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, |
275 | sht21, sht21_groups); | |
276 | return PTR_ERR_OR_ZERO(hwmon_dev); | |
430400b8 UF |
277 | } |
278 | ||
279 | /* Device ID table */ | |
280 | static const struct i2c_device_id sht21_id[] = { | |
281 | { "sht21", 0 }, | |
282 | { } | |
283 | }; | |
284 | MODULE_DEVICE_TABLE(i2c, sht21_id); | |
285 | ||
286 | static struct i2c_driver sht21_driver = { | |
287 | .driver.name = "sht21", | |
1975d167 | 288 | .probe = sht21_probe, |
430400b8 UF |
289 | .id_table = sht21_id, |
290 | }; | |
291 | ||
f0967eea | 292 | module_i2c_driver(sht21_driver); |
430400b8 UF |
293 | |
294 | MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>"); | |
295 | MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver"); | |
296 | MODULE_LICENSE("GPL"); |