hwmon: add support for Sensirion SHTC1 sensor

Add support for Sensirion SHTC1 and compatible temperature and humidity
sensors.

Signed-off-by: Tomas Pop <tomas.pop@sensirion.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

5 files changed, 328 insertions, 0 deletions

diff --git a/Documentation/hwmon/shtc1 b/Documentation/hwmon/shtc1
new file mode 100644
index 000000000000..6b1e05458f0f
--- /dev/null
+++ b/Documentation/hwmon/shtc1
@@ -0,0 +1,43 @@
+Kernel driver shtc1
+===================
+
+Supported chips:
+  * Sensirion SHTC1
+    Prefix: 'shtc1'
+    Addresses scanned: none
+    Datasheet: http://www.sensirion.com/file/datasheet_shtc1
+
+  * Sensirion SHTW1
+    Prefix: 'shtw1'
+    Addresses scanned: none
+    Datasheet: Not publicly available
+
+Author:
+  Johannes Winkelmann <johannes.winkelmann@sensirion.com>
+
+Description
+-----------
+
+This driver implements support for the Sensirion SHTC1 chip, a humidity and
+temperature sensor. Temperature is measured in degrees celsius, relative
+humidity is expressed as a percentage. Driver can be used as well for SHTW1
+chip, which has the same electrical interface.
+
+The device communicates with the I2C protocol. All sensors are set to I2C
+address 0x70. See Documentation/i2c/instantiating-devices for methods to
+instantiate the device.
+
+There are two options configurable by means of shtc1_platform_data:
+1. blocking (pull the I2C clock line down while performing the measurement) or
+   non-blocking mode. Blocking mode will guarantee the fastest result but
+   the I2C bus will be busy during that time. By default, non-blocking mode
+   is used. Make sure clock-stretching works properly on your device if you
+   want to use blocking mode.
+2. high or low accuracy. High accuracy is used by default and using it is
+   strongly recommended.
+
+sysfs-Interface
+---------------
+
+temp1_input - temperature input
+humidity1_input - humidity input
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 00343166feb1..08531a128f53 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1124,6 +1124,16 @@ config SENSORS_SHT21
           This driver can also be built as a module.  If so, the module
           will be called sht21.
 
+config SENSORS_SHTC1
+        tristate "Sensiron humidity and temperature sensors. SHTC1 and compat."
+        depends on I2C
+        help
+          If you say yes here you get support for the Sensiron SHTC1 and SHTW1
+          humidity and temperature sensors.
+
+          This driver can also be built as a module.  If so, the module
+          will be called shtc1.
+
 config SENSORS_S3C
         tristate "Samsung built-in ADC"
         depends on S3C_ADC
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 11798ad7e801..3dc0f02f71d2 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -126,6 +126,7 @@ obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o
 obj-$(CONFIG_SENSORS_SCH5636)   += sch5636.o
 obj-$(CONFIG_SENSORS_SHT15)     += sht15.o
 obj-$(CONFIG_SENSORS_SHT21)     += sht21.o
+obj-$(CONFIG_SENSORS_SHTC1)     += shtc1.o
 obj-$(CONFIG_SENSORS_SIS5595)   += sis5595.o
 obj-$(CONFIG_SENSORS_SMM665)    += smm665.o
 obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
diff --git a/drivers/hwmon/shtc1.c b/drivers/hwmon/shtc1.c
new file mode 100644
index 000000000000..decd7df995ab
--- /dev/null
+++ b/drivers/hwmon/shtc1.c
@@ -0,0 +1,251 @@
+/* Sensirion SHTC1 humidity and temperature sensor driver
+ *
+ * Copyright (C) 2014 Sensirion AG, Switzerland
+ * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/platform_data/shtc1.h>
+
+/* commands (high precision mode) */
+static const unsigned char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
+static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
+
+/* commands (low precision mode) */
+static const unsigned char shtc1_cmd_measure_blocking_lpm[]    = { 0x64, 0x58 };
+static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
+
+/* command for reading the ID register */
+static const unsigned char shtc1_cmd_read_id_reg[]             = { 0xef, 0xc8 };
+
+/* constants for reading the ID register */
+#define SHTC1_ID          0x07
+#define SHTC1_ID_REG_MASK 0x1f
+
+/* delays for non-blocking i2c commands, both in us */
+#define SHTC1_NONBLOCKING_WAIT_TIME_HPM  14400
+#define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1000
+
+#define SHTC1_CMD_LENGTH      2
+#define SHTC1_RESPONSE_LENGTH 6
+
+struct shtc1_data {
+        struct i2c_client *client;
+        struct mutex update_lock;
+        bool valid;
+        unsigned long last_updated; /* in jiffies */
+
+        const unsigned char *command;
+        unsigned int nonblocking_wait_time; /* in us */
+
+        struct shtc1_platform_data setup;
+
+        int temperature; /* 1000 * temperature in dgr C */
+        int humidity; /* 1000 * relative humidity in %RH */
+};
+
+static int shtc1_update_values(struct i2c_client *client,
+                               struct shtc1_data *data,
+                               char *buf, int bufsize)
+{
+        int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
+        if (ret != SHTC1_CMD_LENGTH) {
+                dev_err(&client->dev, "failed to send command: %d\n", ret);
+                return ret < 0 ? ret : -EIO;
+        }
+
+        /*
+         * In blocking mode (clock stretching mode) the I2C bus
+         * is blocked for other traffic, thus the call to i2c_master_recv()
+         * will wait until the data is ready. For non blocking mode, we
+         * have to wait ourselves.
+         */
+        if (!data->setup.blocking_io)
+                usleep_range(data->nonblocking_wait_time,
+                             data->nonblocking_wait_time + 1000);
+
+        ret = i2c_master_recv(client, buf, bufsize);
+        if (ret != bufsize) {
+                dev_err(&client->dev, "failed to read values: %d\n", ret);
+                return ret < 0 ? ret : -EIO;
+        }
+
+        return 0;
+}
+
+/* sysfs attributes */
+static struct shtc1_data *shtc1_update_client(struct device *dev)
+{
+        struct shtc1_data *data = dev_get_drvdata(dev);
+        struct i2c_client *client = data->client;
+        unsigned char buf[SHTC1_RESPONSE_LENGTH];
+        int val;
+        int ret = 0;
+
+        mutex_lock(&data->update_lock);
+
+        if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
+                ret = shtc1_update_values(client, data, buf, sizeof(buf));
+                if (ret)
+                        goto out;
+
+                /*
+                 * From datasheet:
+                 * T = -45 + 175 * ST / 2^16
+                 * RH = 100 * SRH / 2^16
+                 *
+                 * Adapted for integer fixed point (3 digit) arithmetic.
+                 */
+                val = be16_to_cpup((__be16 *)buf);
+                data->temperature = ((21875 * val) >> 13) - 45000;
+                val = be16_to_cpup((__be16 *)(buf + 3));
+                data->humidity = ((12500 * val) >> 13);
+
+                data->last_updated = jiffies;
+                data->valid = true;
+        }
+
+out:
+        mutex_unlock(&data->update_lock);
+
+        return ret == 0 ? data : ERR_PTR(ret);
+}
+
+static ssize_t temp1_input_show(struct device *dev,
+                                struct device_attribute *attr,
+                                char *buf)
+{
+        struct shtc1_data *data = shtc1_update_client(dev);
+        if (IS_ERR(data))
+                return PTR_ERR(data);
+
+        return sprintf(buf, "%d\n", data->temperature);
+}
+
+static ssize_t humidity1_input_show(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+        struct shtc1_data *data = shtc1_update_client(dev);
+        if (IS_ERR(data))
+                return PTR_ERR(data);
+
+        return sprintf(buf, "%d\n", data->humidity);
+}
+
+static DEVICE_ATTR_RO(temp1_input);
+static DEVICE_ATTR_RO(humidity1_input);
+
+static struct attribute *shtc1_attrs[] = {
+        &dev_attr_temp1_input.attr,
+        &dev_attr_humidity1_input.attr,
+        NULL
+};
+
+ATTRIBUTE_GROUPS(shtc1);
+
+static void shtc1_select_command(struct shtc1_data *data)
+{
+        if (data->setup.high_precision) {
+                data->command = data->setup.blocking_io ?
+                                shtc1_cmd_measure_blocking_hpm :
+                                shtc1_cmd_measure_nonblocking_hpm;
+                data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM;
+
+        } else {
+                data->command = data->setup.blocking_io ?
+                                shtc1_cmd_measure_blocking_lpm :
+                                shtc1_cmd_measure_nonblocking_lpm;
+                data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM;
+        }
+}
+
+static int shtc1_probe(struct i2c_client *client,
+                       const struct i2c_device_id *id)
+{
+        int ret;
+        char id_reg[2];
+        struct shtc1_data *data;
+        struct device *hwmon_dev;
+        struct i2c_adapter *adap = client->adapter;
+        struct device *dev = &client->dev;
+
+        if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
+                dev_err(dev, "plain i2c transactions not supported\n");
+                return -ENODEV;
+        }
+
+        ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
+        if (ret != SHTC1_CMD_LENGTH) {
+                dev_err(dev, "could not send read_id_reg command: %d\n", ret);
+                return ret < 0 ? ret : -ENODEV;
+        }
+        ret = i2c_master_recv(client, id_reg, sizeof(id_reg));
+        if (ret != sizeof(id_reg)) {
+                dev_err(dev, "could not read ID register: %d\n", ret);
+                return -ENODEV;
+        }
+        if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) {
+                dev_err(dev, "ID register doesn't match\n");
+                return -ENODEV;
+        }
+
+        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        data->setup.blocking_io = false;
+        data->setup.high_precision = true;
+        data->client = client;
+
+        if (client->dev.platform_data)
+                data->setup = *(struct shtc1_platform_data *)dev->platform_data;
+        shtc1_select_command(data);
+        mutex_init(&data->update_lock);
+
+        hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+                                                           client->name,
+                                                           data,
+                                                           shtc1_groups);
+        if (IS_ERR(hwmon_dev))
+                dev_dbg(dev, "unable to register hwmon device\n");
+
+        return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+/* device ID table */
+static const struct i2c_device_id shtc1_id[] = {
+        { "shtc1", 0 },
+        { "shtw1", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, shtc1_id);
+
+static struct i2c_driver shtc1_i2c_driver = {
+        .driver.name  = "shtc1",
+        .probe        = shtc1_probe,
+        .id_table     = shtc1_id,
+};
+
+module_i2c_driver(shtc1_i2c_driver);
+
+MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
+MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/platform_data/shtc1.h b/include/linux/platform_data/shtc1.h
new file mode 100644
index 000000000000..7b8c353f7dc8
--- /dev/null
+++ b/include/linux/platform_data/shtc1.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2014 Sensirion AG, Switzerland
+ * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __SHTC1_H_
+#define __SHTC1_H_
+
+struct shtc1_platform_data {
+        bool blocking_io;
+        bool high_precision;
+};
+#endif /* __SHTC1_H_ */