drivers/hwmon/shtc1.c

   1 /* Sensirion SHTC1 humidity and temperature sensor driver
   2  *
   3  * Copyright (C) 2014 Sensirion AG, Switzerland
   4  * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  */
  17
  18 #include <linux/module.h>
  19 #include <linux/init.h>
  20 #include <linux/slab.h>
  21 #include <linux/i2c.h>
  22 #include <linux/hwmon.h>
  23 #include <linux/hwmon-sysfs.h>
  24 #include <linux/err.h>
  25 #include <linux/delay.h>
  26 #include <linux/platform_data/shtc1.h>
  27
  28 /* commands (high precision mode) */
  29 static const unsigned char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
  30 static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
  31
  32 /* commands (low precision mode) */
  33 static const unsigned char shtc1_cmd_measure_blocking_lpm[]    = { 0x64, 0x58 };
  34 static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
  35
  36 /* command for reading the ID register */
  37 static const unsigned char shtc1_cmd_read_id_reg[]             = { 0xef, 0xc8 };
  38
  39 /* constants for reading the ID register */
  40 #define SHTC1_ID          0x07
  41 #define SHTC1_ID_REG_MASK 0x3f
  42
  43 /* delays for non-blocking i2c commands, both in us */
  44 #define SHTC1_NONBLOCKING_WAIT_TIME_HPM  14400
  45 #define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1000
  46
  47 #define SHTC1_CMD_LENGTH      2
  48 #define SHTC1_RESPONSE_LENGTH 6
  49
  50 struct shtc1_data {
  51         struct i2c_client *client;
  52         struct mutex update_lock;
  53         bool valid;
  54         unsigned long last_updated; /* in jiffies */
  55
  56         const unsigned char *command;
  57         unsigned int nonblocking_wait_time; /* in us */
  58
  59         struct shtc1_platform_data setup;
  60
  61         int temperature; /* 1000 * temperature in dgr C */
  62         int humidity; /* 1000 * relative humidity in %RH */
  63 };
  64
  65 static int shtc1_update_values(struct i2c_client *client,
  66                                struct shtc1_data *data,
  67                                char *buf, int bufsize)
  68 {
  69         int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
  70         if (ret != SHTC1_CMD_LENGTH) {
  71                 dev_err(&client->dev, "failed to send command: %d\n", ret);
  72                 return ret < 0 ? ret : -EIO;
  73         }
  74
  75         /*
  76          * In blocking mode (clock stretching mode) the I2C bus
  77          * is blocked for other traffic, thus the call to i2c_master_recv()
  78          * will wait until the data is ready. For non blocking mode, we
  79          * have to wait ourselves.
  80          */
  81         if (!data->setup.blocking_io)
  82                 usleep_range(data->nonblocking_wait_time,
  83                              data->nonblocking_wait_time + 1000);
  84
  85         ret = i2c_master_recv(client, buf, bufsize);
  86         if (ret != bufsize) {
  87                 dev_err(&client->dev, "failed to read values: %d\n", ret);
  88                 return ret < 0 ? ret : -EIO;
  89         }
  90
  91         return 0;
  92 }
  93
  94 /* sysfs attributes */
  95 static struct shtc1_data *shtc1_update_client(struct device *dev)
  96 {
  97         struct shtc1_data *data = dev_get_drvdata(dev);
  98         struct i2c_client *client = data->client;
  99         unsigned char buf[SHTC1_RESPONSE_LENGTH];
 100         int val;
 101         int ret = 0;
 102
 103         mutex_lock(&data->update_lock);
 104
 105         if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
 106                 ret = shtc1_update_values(client, data, buf, sizeof(buf));
 107                 if (ret)
 108                         goto out;
 109
 110                 /*
 111                  * From datasheet:
 112                  * T = -45 + 175 * ST / 2^16
 113                  * RH = 100 * SRH / 2^16
 114                  *
 115                  * Adapted for integer fixed point (3 digit) arithmetic.
 116                  */
 117                 val = be16_to_cpup((__be16 *)buf);
 118                 data->temperature = ((21875 * val) >> 13) - 45000;
 119                 val = be16_to_cpup((__be16 *)(buf + 3));
 120                 data->humidity = ((12500 * val) >> 13);
 121
 122                 data->last_updated = jiffies;
 123                 data->valid = true;
 124         }
 125
 126 out:
 127         mutex_unlock(&data->update_lock);
 128
 129         return ret == 0 ? data : ERR_PTR(ret);
 130 }
 131
 132 static ssize_t temp1_input_show(struct device *dev,
 133                                 struct device_attribute *attr,
 134                                 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->temperature);
 141 }
 142
 143 static ssize_t humidity1_input_show(struct device *dev,
 144                                     struct device_attribute *attr, char *buf)
 145 {
 146         struct shtc1_data *data = shtc1_update_client(dev);
 147         if (IS_ERR(data))
 148                 return PTR_ERR(data);
 149
 150         return sprintf(buf, "%d\n", data->humidity);
 151 }
 152
 153 static DEVICE_ATTR_RO(temp1_input);
 154 static DEVICE_ATTR_RO(humidity1_input);
 155
 156 static struct attribute *shtc1_attrs[] = {
 157         &dev_attr_temp1_input.attr,
 158         &dev_attr_humidity1_input.attr,
 159         NULL
 160 };
 161
 162 ATTRIBUTE_GROUPS(shtc1);
 163
 164 static void shtc1_select_command(struct shtc1_data *data)
 165 {
 166         if (data->setup.high_precision) {
 167                 data->command = data->setup.blocking_io ?
 168                                 shtc1_cmd_measure_blocking_hpm :
 169                                 shtc1_cmd_measure_nonblocking_hpm;
 170                 data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM;
 171
 172         } else {
 173                 data->command = data->setup.blocking_io ?
 174                                 shtc1_cmd_measure_blocking_lpm :
 175                                 shtc1_cmd_measure_nonblocking_lpm;
 176                 data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM;
 177         }
 178 }
 179
 180 static int shtc1_probe(struct i2c_client *client,
 181                        const struct i2c_device_id *id)
 182 {
 183         int ret;
 184         char id_reg[2];
 185         struct shtc1_data *data;
 186         struct device *hwmon_dev;
 187         struct i2c_adapter *adap = client->adapter;
 188         struct device *dev = &client->dev;
 189
 190         if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
 191                 dev_err(dev, "plain i2c transactions not supported\n");
 192                 return -ENODEV;
 193         }
 194
 195         ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
 196         if (ret != SHTC1_CMD_LENGTH) {
 197                 dev_err(dev, "could not send read_id_reg command: %d\n", ret);
 198                 return ret < 0 ? ret : -ENODEV;
 199         }
 200         ret = i2c_master_recv(client, id_reg, sizeof(id_reg));
 201         if (ret != sizeof(id_reg)) {
 202                 dev_err(dev, "could not read ID register: %d\n", ret);
 203                 return -ENODEV;
 204         }
 205         if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) {
 206                 dev_err(dev, "ID register doesn't match\n");
 207                 return -ENODEV;
 208         }
 209
 210         data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 211         if (!data)
 212                 return -ENOMEM;
 213
 214         data->setup.blocking_io = false;
 215         data->setup.high_precision = true;
 216         data->client = client;
 217
 218         if (client->dev.platform_data)
 219                 data->setup = *(struct shtc1_platform_data *)dev->platform_data;
 220         shtc1_select_command(data);
 221         mutex_init(&data->update_lock);
 222
 223         hwmon_dev = devm_hwmon_device_register_with_groups(dev,
 224                                                            client->name,
 225                                                            data,
 226                                                            shtc1_groups);
 227         if (IS_ERR(hwmon_dev))
 228                 dev_dbg(dev, "unable to register hwmon device\n");
 229
 230         return PTR_ERR_OR_ZERO(hwmon_dev);
 231 }
 232
 233 /* device ID table */
 234 static const struct i2c_device_id shtc1_id[] = {
 235         { "shtc1", 0 },
 236         { "shtw1", 0 },
 237         { }
 238 };
 239 MODULE_DEVICE_TABLE(i2c, shtc1_id);
 240
 241 static struct i2c_driver shtc1_i2c_driver = {
 242         .driver.name  = "shtc1",
 243         .probe        = shtc1_probe,
 244         .id_table     = shtc1_id,
 245 };
 246
 247 module_i2c_driver(shtc1_i2c_driver);
 248
 249 MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
 250 MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
 251 MODULE_LICENSE("GPL");