xref: /linux/drivers/hwmon/shtc1.c (revision a1ff5a7d78a036d6c2178ee5acd6ba4946243800)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Sensirion SHTC1 humidity and temperature sensor driver
3  *
4  * Copyright (C) 2014 Sensirion AG, Switzerland
5  * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
6  */
7 
8 #include <linux/module.h>
9 #include <linux/init.h>
10 #include <linux/slab.h>
11 #include <linux/i2c.h>
12 #include <linux/hwmon.h>
13 #include <linux/hwmon-sysfs.h>
14 #include <linux/err.h>
15 #include <linux/delay.h>
16 #include <linux/platform_data/shtc1.h>
17 #include <linux/of.h>
18 
19 /* commands (high precision mode) */
20 static const unsigned char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
21 static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
22 
23 /* commands (low precision mode) */
24 static const unsigned char shtc1_cmd_measure_blocking_lpm[]    = { 0x64, 0x58 };
25 static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
26 
27 /* command for reading the ID register */
28 static const unsigned char shtc1_cmd_read_id_reg[]             = { 0xef, 0xc8 };
29 
30 /*
31  * constants for reading the ID register
32  * SHTC1: 0x0007 with mask 0x003f
33  * SHTW1: 0x0007 with mask 0x003f
34  * SHTC3: 0x0807 with mask 0x083f
35  */
36 #define SHTC3_ID      0x0807
37 #define SHTC3_ID_MASK 0x083f
38 #define SHTC1_ID      0x0007
39 #define SHTC1_ID_MASK 0x003f
40 
41 /* delays for non-blocking i2c commands, both in us */
42 #define SHTC1_NONBLOCKING_WAIT_TIME_HPM  14400
43 #define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1000
44 #define SHTC3_NONBLOCKING_WAIT_TIME_HPM  12100
45 #define SHTC3_NONBLOCKING_WAIT_TIME_LPM    800
46 
47 #define SHTC1_CMD_LENGTH      2
48 #define SHTC1_RESPONSE_LENGTH 6
49 
50 enum shtcx_chips {
51 	shtc1,
52 	shtc3,
53 };
54 
55 struct shtc1_data {
56 	struct i2c_client *client;
57 	struct mutex update_lock;
58 	bool valid;
59 	unsigned long last_updated; /* in jiffies */
60 
61 	const unsigned char *command;
62 	unsigned int nonblocking_wait_time; /* in us */
63 
64 	struct shtc1_platform_data setup;
65 	enum shtcx_chips chip;
66 
67 	int temperature; /* 1000 * temperature in dgr C */
68 	int humidity; /* 1000 * relative humidity in %RH */
69 };
70 
shtc1_update_values(struct i2c_client * client,struct shtc1_data * data,char * buf,int bufsize)71 static int shtc1_update_values(struct i2c_client *client,
72 			       struct shtc1_data *data,
73 			       char *buf, int bufsize)
74 {
75 	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
76 	if (ret != SHTC1_CMD_LENGTH) {
77 		dev_err(&client->dev, "failed to send command: %d\n", ret);
78 		return ret < 0 ? ret : -EIO;
79 	}
80 
81 	/*
82 	 * In blocking mode (clock stretching mode) the I2C bus
83 	 * is blocked for other traffic, thus the call to i2c_master_recv()
84 	 * will wait until the data is ready. For non blocking mode, we
85 	 * have to wait ourselves.
86 	 */
87 	if (!data->setup.blocking_io)
88 		usleep_range(data->nonblocking_wait_time,
89 			     data->nonblocking_wait_time + 1000);
90 
91 	ret = i2c_master_recv(client, buf, bufsize);
92 	if (ret != bufsize) {
93 		dev_err(&client->dev, "failed to read values: %d\n", ret);
94 		return ret < 0 ? ret : -EIO;
95 	}
96 
97 	return 0;
98 }
99 
100 /* sysfs attributes */
shtc1_update_client(struct device * dev)101 static struct shtc1_data *shtc1_update_client(struct device *dev)
102 {
103 	struct shtc1_data *data = dev_get_drvdata(dev);
104 	struct i2c_client *client = data->client;
105 	unsigned char buf[SHTC1_RESPONSE_LENGTH];
106 	int val;
107 	int ret = 0;
108 
109 	mutex_lock(&data->update_lock);
110 
111 	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
112 		ret = shtc1_update_values(client, data, buf, sizeof(buf));
113 		if (ret)
114 			goto out;
115 
116 		/*
117 		 * From datasheet:
118 		 * T = -45 + 175 * ST / 2^16
119 		 * RH = 100 * SRH / 2^16
120 		 *
121 		 * Adapted for integer fixed point (3 digit) arithmetic.
122 		 */
123 		val = be16_to_cpup((__be16 *)buf);
124 		data->temperature = ((21875 * val) >> 13) - 45000;
125 		val = be16_to_cpup((__be16 *)(buf + 3));
126 		data->humidity = ((12500 * val) >> 13);
127 
128 		data->last_updated = jiffies;
129 		data->valid = true;
130 	}
131 
132 out:
133 	mutex_unlock(&data->update_lock);
134 
135 	return ret == 0 ? data : ERR_PTR(ret);
136 }
137 
temp1_input_show(struct device * dev,struct device_attribute * attr,char * buf)138 static ssize_t temp1_input_show(struct device *dev,
139 				struct device_attribute *attr,
140 				char *buf)
141 {
142 	struct shtc1_data *data = shtc1_update_client(dev);
143 	if (IS_ERR(data))
144 		return PTR_ERR(data);
145 
146 	return sprintf(buf, "%d\n", data->temperature);
147 }
148 
humidity1_input_show(struct device * dev,struct device_attribute * attr,char * buf)149 static ssize_t humidity1_input_show(struct device *dev,
150 				    struct device_attribute *attr, char *buf)
151 {
152 	struct shtc1_data *data = shtc1_update_client(dev);
153 	if (IS_ERR(data))
154 		return PTR_ERR(data);
155 
156 	return sprintf(buf, "%d\n", data->humidity);
157 }
158 
159 static DEVICE_ATTR_RO(temp1_input);
160 static DEVICE_ATTR_RO(humidity1_input);
161 
162 static struct attribute *shtc1_attrs[] = {
163 	&dev_attr_temp1_input.attr,
164 	&dev_attr_humidity1_input.attr,
165 	NULL
166 };
167 
168 ATTRIBUTE_GROUPS(shtc1);
169 
shtc1_select_command(struct shtc1_data * data)170 static void shtc1_select_command(struct shtc1_data *data)
171 {
172 	if (data->setup.high_precision) {
173 		data->command = data->setup.blocking_io ?
174 				shtc1_cmd_measure_blocking_hpm :
175 				shtc1_cmd_measure_nonblocking_hpm;
176 		data->nonblocking_wait_time = (data->chip == shtc1) ?
177 				SHTC1_NONBLOCKING_WAIT_TIME_HPM :
178 				SHTC3_NONBLOCKING_WAIT_TIME_HPM;
179 	} else {
180 		data->command = data->setup.blocking_io ?
181 				shtc1_cmd_measure_blocking_lpm :
182 				shtc1_cmd_measure_nonblocking_lpm;
183 		data->nonblocking_wait_time = (data->chip == shtc1) ?
184 				SHTC1_NONBLOCKING_WAIT_TIME_LPM :
185 				SHTC3_NONBLOCKING_WAIT_TIME_LPM;
186 	}
187 }
188 
shtc1_probe(struct i2c_client * client)189 static int shtc1_probe(struct i2c_client *client)
190 {
191 	int ret;
192 	u16 id_reg;
193 	char id_reg_buf[2];
194 	struct shtc1_data *data;
195 	struct device *hwmon_dev;
196 	enum shtcx_chips chip = (uintptr_t)i2c_get_match_data(client);
197 	struct i2c_adapter *adap = client->adapter;
198 	struct device *dev = &client->dev;
199 	struct device_node *np = dev->of_node;
200 
201 	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
202 		dev_err(dev, "plain i2c transactions not supported\n");
203 		return -ENODEV;
204 	}
205 
206 	ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
207 	if (ret != SHTC1_CMD_LENGTH) {
208 		dev_err(dev, "could not send read_id_reg command: %d\n", ret);
209 		return ret < 0 ? ret : -ENODEV;
210 	}
211 	ret = i2c_master_recv(client, id_reg_buf, sizeof(id_reg_buf));
212 	if (ret != sizeof(id_reg_buf)) {
213 		dev_err(dev, "could not read ID register: %d\n", ret);
214 		return -ENODEV;
215 	}
216 
217 	id_reg = be16_to_cpup((__be16 *)id_reg_buf);
218 	if (chip == shtc3) {
219 		if ((id_reg & SHTC3_ID_MASK) != SHTC3_ID) {
220 			dev_err(dev, "SHTC3 ID register does not match\n");
221 			return -ENODEV;
222 		}
223 	} else if ((id_reg & SHTC1_ID_MASK) != SHTC1_ID) {
224 		dev_err(dev, "SHTC1 ID register does not match\n");
225 		return -ENODEV;
226 	}
227 
228 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
229 	if (!data)
230 		return -ENOMEM;
231 
232 	data->setup.blocking_io = false;
233 	data->setup.high_precision = true;
234 	data->client = client;
235 	data->chip = chip;
236 
237 	if (np) {
238 		data->setup.blocking_io = of_property_read_bool(np, "sensirion,blocking-io");
239 		data->setup.high_precision = !of_property_read_bool(np, "sensirion,low-precision");
240 	} else {
241 		if (client->dev.platform_data)
242 			data->setup = *(struct shtc1_platform_data *)dev->platform_data;
243 	}
244 
245 	shtc1_select_command(data);
246 	mutex_init(&data->update_lock);
247 
248 	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
249 							   client->name,
250 							   data,
251 							   shtc1_groups);
252 	if (IS_ERR(hwmon_dev))
253 		dev_dbg(dev, "unable to register hwmon device\n");
254 
255 	return PTR_ERR_OR_ZERO(hwmon_dev);
256 }
257 
258 /* device ID table */
259 static const struct i2c_device_id shtc1_id[] = {
260 	{ "shtc1", shtc1 },
261 	{ "shtw1", shtc1 },
262 	{ "shtc3", shtc3 },
263 	{ }
264 };
265 MODULE_DEVICE_TABLE(i2c, shtc1_id);
266 
267 static const struct of_device_id shtc1_of_match[] = {
268 	{ .compatible = "sensirion,shtc1" },
269 	{ .compatible = "sensirion,shtw1" },
270 	{ .compatible = "sensirion,shtc3" },
271 	{ }
272 };
273 MODULE_DEVICE_TABLE(of, shtc1_of_match);
274 
275 static struct i2c_driver shtc1_i2c_driver = {
276 	.driver = {
277 		.name = "shtc1",
278 		.of_match_table = shtc1_of_match,
279 	},
280 	.probe        = shtc1_probe,
281 	.id_table     = shtc1_id,
282 };
283 
284 module_i2c_driver(shtc1_i2c_driver);
285 
286 MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
287 MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
288 MODULE_LICENSE("GPL");
289