hwmon: add driver for Microchip TC74

Add hwmon driver for the Microchip TC74.

The TC74 is a single-input 8-bit I2C temperature sensor,
with +-2 degrees centigrade accuracy.

Signed-off-by: Maciej Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

4 files changed, 208 insertions, 0 deletions

diff --git a/Documentation/hwmon/tc74 b/Documentation/hwmon/tc74
new file mode 100644
index 000000000000..43027aad5f8e
--- /dev/null
+++ b/Documentation/hwmon/tc74
@@ -0,0 +1,20 @@
+Kernel driver tc74
+====================
+
+Supported chips:
+   * Microchip TC74
+     Prefix: 'tc74'
+     Datasheet: Publicly available at Microchip website.
+
+Description
+-----------
+
+Driver supports the above part.
+
+The tc74 has an 8-bit sensor, with 1 degree centigrade resolution
+and +- 2 degrees centigrade accuracy.
+
+Notes
+-----
+
+Currently entering low power standby mode is not supported.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 9c9d38b1e92e..54075a07d2a1 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1452,6 +1452,16 @@ config SENSORS_INA2XX
           This driver can also be built as a module.  If so, the module
           will be called ina2xx.
 
+config SENSORS_TC74
+        tristate "Microchip TC74"
+        depends on I2C
+        help
+          If you say yes here you get support for Microchip TC74 single
+          input temperature sensor chips.
+
+          This driver can also be built as a module.  If so, the module
+          will be called tc74.
+
 config SENSORS_THMC50
         tristate "Texas Instruments THMC50 / Analog Devices ADM1022"
         depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index b4a40f17e2aa..ab904027f074 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -140,6 +140,7 @@ obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
 obj-$(CONFIG_SENSORS_SMSC47M1)  += smsc47m1.o
 obj-$(CONFIG_SENSORS_SMSC47M192)+= smsc47m192.o
 obj-$(CONFIG_SENSORS_AMC6821)   += amc6821.o
+obj-$(CONFIG_SENSORS_TC74)      += tc74.o
 obj-$(CONFIG_SENSORS_THMC50)    += thmc50.o
 obj-$(CONFIG_SENSORS_TMP102)    += tmp102.o
 obj-$(CONFIG_SENSORS_TMP103)    += tmp103.o
diff --git a/drivers/hwmon/tc74.c b/drivers/hwmon/tc74.c
new file mode 100644
index 000000000000..d95165158800
--- /dev/null
+++ b/drivers/hwmon/tc74.c
@@ -0,0 +1,177 @@
+/*
+ * An hwmon driver for the Microchip TC74
+ *
+ * Copyright 2015 Maciej Szmigiero <mail@maciej.szmigiero.name>
+ *
+ * Based on ad7414.c:
+ *      Copyright 2006 Stefan Roese, DENX Software Engineering
+ *      Copyright 2008 Sean MacLennan, PIKA Technologies
+ *      Copyright 2008 Frank Edelhaeuser, Spansion Inc.
+ *
+ * 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.
+ */
+
+#include <linux/bitops.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+/* TC74 registers */
+#define TC74_REG_TEMP           0x00
+#define TC74_REG_CONFIG         0x01
+
+struct tc74_data {
+        struct i2c_client       *client;
+        struct mutex            lock;   /* atomic read data updates */
+        bool                    valid;  /* validity of fields below */
+        unsigned long           next_update;    /* In jiffies */
+        s8                      temp_input;     /* Temp value in dC */
+};
+
+static int tc74_update_device(struct device *dev)
+{
+        struct tc74_data *data = dev_get_drvdata(dev);
+        struct i2c_client *client = data->client;
+        int ret;
+
+        ret = mutex_lock_interruptible(&data->lock);
+        if (ret)
+                return ret;
+
+        if (time_after(jiffies, data->next_update) || !data->valid) {
+                s32 value;
+
+                value = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
+                if (value < 0) {
+                        dev_dbg(&client->dev, "TC74_REG_CONFIG read err %d\n",
+                                (int)value);
+
+                        ret = value;
+                        goto ret_unlock;
+                }
+
+                if (!(value & BIT(6))) {
+                        /* not ready yet */
+
+                        ret = -EAGAIN;
+                        goto ret_unlock;
+                }
+
+                value = i2c_smbus_read_byte_data(client, TC74_REG_TEMP);
+                if (value < 0) {
+                        dev_dbg(&client->dev, "TC74_REG_TEMP read err %d\n",
+                                (int)value);
+
+                        ret = value;
+                        goto ret_unlock;
+                }
+
+                data->temp_input = value;
+                data->next_update = jiffies + HZ / 4;
+                data->valid = true;
+        }
+
+ret_unlock:
+        mutex_unlock(&data->lock);
+
+        return ret;
+}
+
+static ssize_t show_temp_input(struct device *dev,
+                               struct device_attribute *attr, char *buf)
+{
+        struct tc74_data *data = dev_get_drvdata(dev);
+        int ret;
+
+        ret = tc74_update_device(dev);
+        if (ret)
+                return ret;
+
+        return sprintf(buf, "%d\n", data->temp_input * 1000);
+}
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp_input, NULL, 0);
+
+static struct attribute *tc74_attrs[] = {
+        &sensor_dev_attr_temp1_input.dev_attr.attr,
+        NULL
+};
+
+ATTRIBUTE_GROUPS(tc74);
+
+static int tc74_probe(struct i2c_client *client,
+                      const struct i2c_device_id *dev_id)
+{
+        struct device *dev = &client->dev;
+        struct tc74_data *data;
+        struct device *hwmon_dev;
+        s32 conf;
+
+        if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+                return -EOPNOTSUPP;
+
+        data = devm_kzalloc(dev, sizeof(struct tc74_data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        data->client = client;
+        mutex_init(&data->lock);
+
+        /* Make sure the chip is powered up. */
+        conf = i2c_smbus_read_byte_data(client, TC74_REG_CONFIG);
+        if (conf < 0) {
+                dev_err(dev, "unable to read config register\n");
+
+                return conf;
+        }
+
+        if (conf & 0x3f) {
+                dev_err(dev, "invalid config register value\n");
+
+                return -ENODEV;
+        }
+
+        if (conf & BIT(7)) {
+                s32 ret;
+
+                conf &= ~BIT(7);
+
+                ret = i2c_smbus_write_byte_data(client, TC74_REG_CONFIG, conf);
+                if (ret)
+                        dev_warn(dev, "unable to disable STANDBY\n");
+        }
+
+        hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+                                                           client->name,
+                                                           data, tc74_groups);
+        return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id tc74_id[] = {
+        { "tc74", 0 },
+        {}
+};
+MODULE_DEVICE_TABLE(i2c, tc74_id);
+
+static struct i2c_driver tc74_driver = {
+        .driver = {
+                .name   = "tc74",
+        },
+        .probe  = tc74_probe,
+        .id_table = tc74_id,
+};
+
+module_i2c_driver(tc74_driver);
+
+MODULE_AUTHOR("Maciej Szmigiero <mail@maciej.szmigiero.name>");
+
+MODULE_DESCRIPTION("TC74 driver");
+MODULE_LICENSE("GPL");