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 /* constants for reading the ID register */
  30 #define SHTC1_ID          0x07
  31 #define SHTC1_ID_REG_MASK 0x1f
  32
  33 /* delays for non-blocking i2c commands, both in us */
  34 #define SHTC1_NONBLOCKING_WAIT_TIME_HPM  14400
  35 #define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1000
  36
  37 #define SHTC1_CMD_LENGTH      2
  38 #define SHTC1_RESPONSE_LENGTH 6
  39
  40 struct shtc1_data {
  41         struct i2c_client *client;
  42         struct mutex update_lock;
  43         bool valid;
  44         unsigned long last_updated; /* in jiffies */
  45
  46         const unsigned char *command;
  47         unsigned int nonblocking_wait_time; /* in us */
  48
  49         struct shtc1_platform_data setup;
  50
  51         int temperature; /* 1000 * temperature in dgr C */
  52         int humidity; /* 1000 * relative humidity in %RH */
  53 };
  54
  55 static int shtc1_update_values(struct i2c_client *client,
  56                                struct shtc1_data *data,
  57                                char *buf, int bufsize)
  58 {
  59         int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
  60         if (ret != SHTC1_CMD_LENGTH) {
  61                 dev_err(&client->dev, "failed to send command: %d\n", ret);
  62                 return ret < 0 ? ret : -EIO;
  63         }
  64
  65         /*
  66          * In blocking mode (clock stretching mode) the I2C bus
  67          * is blocked for other traffic, thus the call to i2c_master_recv()
  68          * will wait until the data is ready. For non blocking mode, we
  69          * have to wait ourselves.
  70          */
  71         if (!data->setup.blocking_io)
  72                 usleep_range(data->nonblocking_wait_time,
  73                              data->nonblocking_wait_time + 1000);
  74
  75         ret = i2c_master_recv(client, buf, bufsize);
  76         if (ret != bufsize) {
  77                 dev_err(&client->dev, "failed to read values: %d\n", ret);
  78                 return ret < 0 ? ret : -EIO;
  79         }
  80
  81         return 0;
  82 }
  83
  84 /* sysfs attributes */
  85 static struct shtc1_data *shtc1_update_client(struct device *dev)
  86 {
  87         struct shtc1_data *data = dev_get_drvdata(dev);
  88         struct i2c_client *client = data->client;
  89         unsigned char buf[SHTC1_RESPONSE_LENGTH];
  90         int val;
  91         int ret = 0;
  92
  93         mutex_lock(&data->update_lock);
  94
  95         if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
  96                 ret = shtc1_update_values(client, data, buf, sizeof(buf));
  97                 if (ret)
  98                         goto out;
  99
 100                 /*
 101                  * From datasheet:
 102                  * T = -45 + 175 * ST / 2^16
 103                  * RH = 100 * SRH / 2^16
 104                  *
 105                  * Adapted for integer fixed point (3 digit) arithmetic.
 106                  */
 107                 val = be16_to_cpup((__be16 *)buf);
 108                 data->temperature = ((21875 * val) >> 13) - 45000;
 109                 val = be16_to_cpup((__be16 *)(buf + 3));
 110                 data->humidity = ((12500 * val) >> 13);
 111
 112                 data->last_updated = jiffies;
 113                 data->valid = true;
 114         }
 115
 116 out:
 117         mutex_unlock(&data->update_lock);
 118
 119         return ret == 0 ? data : ERR_PTR(ret);
 120 }
 121
 122 static ssize_t temp1_input_show(struct device *dev,
 123                                 struct device_attribute *attr,
 124                                 char *buf)
 125 {
 126         struct shtc1_data *data = shtc1_update_client(dev);
 127         if (IS_ERR(data))
 128                 return PTR_ERR(data);
 129
 130         return sprintf(buf, "%d\n", data->temperature);
 131 }
 132
 133 static ssize_t humidity1_input_show(struct device *dev,
 134                                     struct device_attribute *attr, char *buf)
 135 {
 136         struct shtc1_data *data = shtc1_update_client(dev);
 137         if (IS_ERR(data))
 138                 return PTR_ERR(data);
 139
 140         return sprintf(buf, "%d\n", data->humidity);
 141 }
 142
 143 static DEVICE_ATTR_RO(temp1_input);
 144 static DEVICE_ATTR_RO(humidity1_input);
 145
 146 static struct attribute *shtc1_attrs[] = {
 147         &dev_attr_temp1_input.attr,
 148         &dev_attr_humidity1_input.attr,
 149         NULL
 150 };
 151
 152 ATTRIBUTE_GROUPS(shtc1);
 153
 154 static void shtc1_select_command(struct shtc1_data *data)
 155 {
 156         if (data->setup.high_precision) {
 157                 data->command = data->setup.blocking_io ?
 158                                 shtc1_cmd_measure_blocking_hpm :
 159                                 shtc1_cmd_measure_nonblocking_hpm;
 160                 data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM;
 161
 162         } else {
 163                 data->command = data->setup.blocking_io ?
 164                                 shtc1_cmd_measure_blocking_lpm :
 165                                 shtc1_cmd_measure_nonblocking_lpm;
 166                 data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM;
 167         }
 168 }
 169
 170 static int shtc1_probe(struct i2c_client *client,
 171                        const struct i2c_device_id *id)
 172 {
 173         int ret;
 174         char id_reg[2];
 175         struct shtc1_data *data;
 176         struct device *hwmon_dev;
 177         struct i2c_adapter *adap = client->adapter;
 178         struct device *dev = &client->dev;
 179
 180         if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
 181                 dev_err(dev, "plain i2c transactions not supported\n");
 182                 return -ENODEV;
 183         }
 184
 185         ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
 186         if (ret != SHTC1_CMD_LENGTH) {
 187                 dev_err(dev, "could not send read_id_reg command: %d\n", ret);
 188                 return ret < 0 ? ret : -ENODEV;
 189         }
 190         ret = i2c_master_recv(client, id_reg, sizeof(id_reg));
 191         if (ret != sizeof(id_reg)) {
 192                 dev_err(dev, "could not read ID register: %d\n", ret);
 193                 return -ENODEV;
 194         }
 195         if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) {
 196                 dev_err(dev, "ID register doesn't match\n");
 197                 return -ENODEV;
 198         }
 199
 200         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 201         if (!data)
 202                 return -ENOMEM;
 203
 204         data->setup.blocking_io = false;
 205         data->setup.high_precision = true;
 206         data->client = client;
 207
 208         if (client->dev.platform_data)
 209                 data->setup = *(struct shtc1_platform_data *)dev->platform_data;
 210         shtc1_select_command(data);
 211         mutex_init(&data->update_lock);
 212
 213         hwmon_dev = devm_hwmon_device_register_with_groups(dev,
 214                                                            client->name,
 215                                                            data,
 216                                                            shtc1_groups);
 217         if (IS_ERR(hwmon_dev))
 218                 dev_dbg(dev, "unable to register hwmon device\n");
 219
 220         return PTR_ERR_OR_ZERO(hwmon_dev);
 221 }
 222
 223 /* device ID table */
 224 static const struct i2c_device_id shtc1_id[] = {
 225         { "shtc1", 0 },
 226         { "shtw1", 0 },
 227         { }
 228 };
 229 MODULE_DEVICE_TABLE(i2c, shtc1_id);
 230
 231 static struct i2c_driver shtc1_i2c_driver = {
 232         .driver.name  = "shtc1",
 233         .probe        = shtc1_probe,
 234         .id_table     = shtc1_id,
 235 };
 236
 237 module_i2c_driver(shtc1_i2c_driver);
 238
 239 MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
 240 MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
 241 MODULE_LICENSE("GPL");