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 */
35struct 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 */
50static 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 */
65static 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 */
81static 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	}
146out:
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 */
161static 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 */
183static 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 */
196static SENSOR_DEVICE_ATTR_RO(temp1_input, hih6130_temperature, 0);
197static SENSOR_DEVICE_ATTR_RO(humidity1_input, hih6130_humidity, 0);
198
199static 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
205ATTRIBUTE_GROUPS(hih6130);
206
207static 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 */
235static const struct i2c_device_id hih6130_id[] = {
236	{ "hih6130", 0 },
237	{ }
238};
239MODULE_DEVICE_TABLE(i2c, hih6130_id);
240
241static const struct of_device_id __maybe_unused hih6130_of_match[] = {
242	{ .compatible = "honeywell,hih6130", },
243	{ }
244};
245MODULE_DEVICE_TABLE(of, hih6130_of_match);
246
247static 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
256module_i2c_driver(hih6130_driver);
257
258MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
259MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
260MODULE_LICENSE("GPL");
261