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_show_temperature() - 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_show_humidity() - 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", 0 },
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_new   = 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