drivers/hwmon/shtc1.c

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