1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver
3 *
4 * Copyright (C) 2012 Iain Paton <ipaton0@gmail.com>
5 *
6 * heavily based on the sht21 driver
7 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
8 *
9 * Data sheets available (2012-06-22) at
10 * http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872
11 */
12
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/slab.h>
16 #include <linux/i2c.h>
17 #include <linux/hwmon.h>
18 #include <linux/hwmon-sysfs.h>
19 #include <linux/err.h>
20 #include <linux/mutex.h>
21 #include <linux/device.h>
22 #include <linux/delay.h>
23 #include <linux/jiffies.h>
24
25 /**
26 * struct hih6130 - HIH-6130 device specific data
27 * @client: pointer to I2C client device
28 * @lock: mutex to protect measurement values
29 * @valid: only false before first measurement is taken
30 * @last_update: time of last update (jiffies)
31 * @temperature: cached temperature measurement value
32 * @humidity: cached humidity measurement value
33 * @write_length: length for I2C measurement request
34 */
35 struct hih6130 {
36 struct i2c_client *client;
37 struct mutex lock;
38 bool valid;
39 unsigned long last_update;
40 int temperature;
41 int humidity;
42 size_t write_length;
43 };
44
45 /**
46 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
47 * milli celsius
48 * @ticks: temperature ticks value received from sensor
49 */
hih6130_temp_ticks_to_millicelsius(int ticks)50 static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
51 {
52 ticks = ticks >> 2;
53 /*
54 * from data sheet section 5.0
55 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
56 */
57 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
58 }
59
60 /**
61 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
62 * one-thousandths of a percent relative humidity
63 * @ticks: humidity ticks value received from sensor
64 */
hih6130_rh_ticks_to_per_cent_mille(int ticks)65 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks)
66 {
67 ticks &= ~0xC000; /* clear status bits */
68 /*
69 * from data sheet section 4.0
70 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100
71 */
72 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100;
73 }
74
75 /**
76 * hih6130_update_measurements() - get updated measurements from device
77 * @dev: device
78 *
79 * Returns 0 on success, else negative errno.
80 */
hih6130_update_measurements(struct device * dev)81 static int hih6130_update_measurements(struct device *dev)
82 {
83 struct hih6130 *hih6130 = dev_get_drvdata(dev);
84 struct i2c_client *client = hih6130->client;
85 int ret = 0;
86 int t;
87 unsigned char tmp[4];
88 struct i2c_msg msgs[1] = {
89 {
90 .addr = client->addr,
91 .flags = I2C_M_RD,
92 .len = 4,
93 .buf = tmp,
94 }
95 };
96
97 mutex_lock(&hih6130->lock);
98
99 /*
100 * While the measurement can be completed in ~40ms the sensor takes
101 * much longer to react to a change in external conditions. How quickly
102 * it reacts depends on airflow and other factors outwith our control.
103 * The datasheet specifies maximum 'Response time' for humidity at 8s
104 * and temperature at 30s under specified conditions.
105 * We therefore choose to only read the sensor at most once per second.
106 * This trades off pointless activity polling the sensor much faster
107 * than it can react against better response times in conditions more
108 * favourable than specified in the datasheet.
109 */
110 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
111
112 /*
113 * Write to slave address to request a measurement.
114 * According with the datasheet it should be with no data, but
115 * for systems with I2C bus drivers that do not allow zero
116 * length packets we write one dummy byte to allow sensor
117 * measurements on them.
118 */
119 tmp[0] = 0;
120 ret = i2c_master_send(client, tmp, hih6130->write_length);
121 if (ret < 0)
122 goto out;
123
124 /* measurement cycle time is ~36.65msec */
125 msleep(40);
126
127 ret = i2c_transfer(client->adapter, msgs, 1);
128 if (ret < 0)
129 goto out;
130
131 if ((tmp[0] & 0xC0) != 0) {
132 dev_err(&client->dev, "Error while reading measurement result\n");
133 ret = -EIO;
134 goto out;
135 }
136
137 t = (tmp[0] << 8) + tmp[1];
138 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);
139
140 t = (tmp[2] << 8) + tmp[3];
141 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);
142
143 hih6130->last_update = jiffies;
144 hih6130->valid = true;
145 }
146 out:
147 mutex_unlock(&hih6130->lock);
148
149 return ret >= 0 ? 0 : ret;
150 }
151
152 /**
153 * hih6130_temperature_show() - show temperature measurement value in sysfs
154 * @dev: device
155 * @attr: device attribute
156 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
157 *
158 * Will be called on read access to temp1_input sysfs attribute.
159 * Returns number of bytes written into buffer, negative errno on error.
160 */
hih6130_temperature_show(struct device * dev,struct device_attribute * attr,char * buf)161 static ssize_t hih6130_temperature_show(struct device *dev,
162 struct device_attribute *attr,
163 char *buf)
164 {
165 struct hih6130 *hih6130 = dev_get_drvdata(dev);
166 int ret;
167
168 ret = hih6130_update_measurements(dev);
169 if (ret < 0)
170 return ret;
171 return sprintf(buf, "%d\n", hih6130->temperature);
172 }
173
174 /**
175 * hih6130_humidity_show() - show humidity measurement value in sysfs
176 * @dev: device
177 * @attr: device attribute
178 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
179 *
180 * Will be called on read access to humidity1_input sysfs attribute.
181 * Returns number of bytes written into buffer, negative errno on error.
182 */
hih6130_humidity_show(struct device * dev,struct device_attribute * attr,char * buf)183 static ssize_t hih6130_humidity_show(struct device *dev,
184 struct device_attribute *attr, char *buf)
185 {
186 struct hih6130 *hih6130 = dev_get_drvdata(dev);
187 int ret;
188
189 ret = hih6130_update_measurements(dev);
190 if (ret < 0)
191 return ret;
192 return sprintf(buf, "%d\n", hih6130->humidity);
193 }
194
195 /* sysfs attributes */
196 static SENSOR_DEVICE_ATTR_RO(temp1_input, hih6130_temperature, 0);
197 static SENSOR_DEVICE_ATTR_RO(humidity1_input, hih6130_humidity, 0);
198
199 static struct attribute *hih6130_attrs[] = {
200 &sensor_dev_attr_temp1_input.dev_attr.attr,
201 &sensor_dev_attr_humidity1_input.dev_attr.attr,
202 NULL
203 };
204
205 ATTRIBUTE_GROUPS(hih6130);
206
hih6130_probe(struct i2c_client * client)207 static int hih6130_probe(struct i2c_client *client)
208 {
209 struct device *dev = &client->dev;
210 struct hih6130 *hih6130;
211 struct device *hwmon_dev;
212
213 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
214 dev_err(&client->dev, "adapter does not support true I2C\n");
215 return -ENODEV;
216 }
217
218 hih6130 = devm_kzalloc(dev, sizeof(*hih6130), GFP_KERNEL);
219 if (!hih6130)
220 return -ENOMEM;
221
222 hih6130->client = client;
223 mutex_init(&hih6130->lock);
224
225 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))
226 hih6130->write_length = 1;
227
228 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
229 hih6130,
230 hih6130_groups);
231 return PTR_ERR_OR_ZERO(hwmon_dev);
232 }
233
234 /* Device ID table */
235 static const struct i2c_device_id hih6130_id[] = {
236 { "hih6130" },
237 { }
238 };
239 MODULE_DEVICE_TABLE(i2c, hih6130_id);
240
241 static const struct of_device_id __maybe_unused hih6130_of_match[] = {
242 { .compatible = "honeywell,hih6130", },
243 { }
244 };
245 MODULE_DEVICE_TABLE(of, hih6130_of_match);
246
247 static struct i2c_driver hih6130_driver = {
248 .driver = {
249 .name = "hih6130",
250 .of_match_table = of_match_ptr(hih6130_of_match),
251 },
252 .probe = hih6130_probe,
253 .id_table = hih6130_id,
254 };
255
256 module_i2c_driver(hih6130_driver);
257
258 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
259 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
260 MODULE_LICENSE("GPL");
261