hwmon: Add support for LTC4151

LTC4151 is High Voltage I2C Current and Voltage Monitor from Linear
Technology.
Signed-off-by: Per Dalen <per.dalen@appeartv.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>

Documentation/hwmon/ltc4151

+Kernel driver ltc4151
+=====================
+
+Supported chips:
+  * Linear Technology LTC4151
+    Prefix: 'ltc4151'
+    Addresses scanned: -
+    Datasheet:
+        http://www.linear.com/docs/Datasheet/4151fc.pdf
+
+Author: Per Dalen <per.dalen@appeartv.com>
+
+
+Description
+-----------
+
+The LTC4151 is a High Voltage I2C Current and Voltage Monitor.
+
+
+Usage Notes
+-----------
+
+This driver does not probe for LTC4151 devices, since there is no register
+which can be safely used to identify the chip. You will have to instantiate
+the devices explicitly.
+
+Example: the following will load the driver for an LTC4151 at address 0x6f
+on I2C bus #0:
+# modprobe ltc4151
+# echo ltc4151 0x6f > /sys/bus/i2c/devices/i2c-0/new_device
+
+
+Sysfs entries
+-------------
+
+Voltage readings provided by this driver are reported as obtained from the ADIN
+and VIN registers.
+
+Current reading provided by this driver is reported as obtained from the Current
+Sense register. The reported value assumes that a 1 mOhm sense resistor is
+installed.
+
+in1_input		VDIN voltage (mV)
+
+in2_input		ADIN voltage (mV)
+
+curr1_input		SENSE current (mA)

drivers/hwmon/Kconfig

@@ -636,6 +636,17 @@ config SENSORS_LM93
 	  This driver can also be built as a module.  If so, the module
 	  will be called lm93.
 
+config SENSORS_LTC4151
+	tristate "Linear Technology LTC4151"
+	depends on I2C
+	default n
+	help
+	  If you say yes here you get support for Linear Technology LTC4151
+	  High Voltage I2C Current and Voltage Monitor interface.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called ltc4151.
+
 config SENSORS_LTC4215
 	tristate "Linear Technology LTC4215"
 	depends on I2C && EXPERIMENTAL

drivers/hwmon/Makefile

@@ -80,6 +80,7 @@ obj-$(CONFIG_SENSORS_LM90)	+= lm90.o
 obj-$(CONFIG_SENSORS_LM92)	+= lm92.o
 obj-$(CONFIG_SENSORS_LM93)	+= lm93.o
 obj-$(CONFIG_SENSORS_LM95241)	+= lm95241.o
+obj-$(CONFIG_SENSORS_LTC4151)	+= ltc4151.o
 obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o
 obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o
 obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o

drivers/hwmon/ltc4151.c

+/*
+ * Driver for Linear Technology LTC4151 High Voltage I2C Current
+ * and Voltage Monitor
+ *
+ * Copyright (C) 2011 AppearTV AS
+ *
+ * Derived from:
+ *
+ *  Driver for Linear Technology LTC4261 I2C Negative Voltage Hot
+ *  Swap Controller
+ *  Copyright (C) 2010 Ericsson AB.
+ *
+ * Datasheet: http://www.linear.com/docs/Datasheet/4151fc.pdf
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+
+/* chip registers */
+#define LTC4151_SENSE_H	0x00
+#define LTC4151_SENSE_L	0x01
+#define LTC4151_VIN_H	0x02
+#define LTC4151_VIN_L	0x03
+#define LTC4151_ADIN_H	0x04
+#define LTC4151_ADIN_L	0x05
+
+struct ltc4151_data {
+	struct device *hwmon_dev;
+
+	struct mutex update_lock;
+	bool valid;
+	unsigned long last_updated; /* in jiffies */
+
+	/* Registers */
+	u8 regs[6];
+};
+
+static struct ltc4151_data *ltc4151_update_device(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ltc4151_data *data = i2c_get_clientdata(client);
+	struct ltc4151_data *ret = data;
+
+	mutex_lock(&data->update_lock);
+
+	/*
+	 * The chip's A/D updates 6 times per second
+	 * (Conversion Rate 6 - 9 Hz)
+	 */
+	if (time_after(jiffies, data->last_updated + HZ / 6) || !data->valid) {
+		int i;
+
+		dev_dbg(&client->dev, "Starting ltc4151 update\n");
+
+		/* Read all registers */
+		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
+			int val;
+
+			val = i2c_smbus_read_byte_data(client, i);
+			if (unlikely(val < 0)) {
+				dev_dbg(dev,
+					"Failed to read ADC value: error %d\n",
+					val);
+				ret = ERR_PTR(val);
+				goto abort;
+			}
+			data->regs[i] = val;
+		}
+		data->last_updated = jiffies;
+		data->valid = 1;
+	}
+abort:
+	mutex_unlock(&data->update_lock);
+	return ret;
+}
+
+/* Return the voltage from the given register in mV */
+static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
+{
+	u32 val;
+
+	val = (data->regs[reg] << 4) + (data->regs[reg + 1] >> 4);
+
+	switch (reg) {
+	case LTC4151_ADIN_H:
+		/* 500uV resolution. Convert to mV. */
+		val = val * 500 / 1000;
+		break;
+	case LTC4151_SENSE_H:
+		/*
+		 * 20uV resolution. Convert to current as measured with
+		 * an 1 mOhm sense resistor, in mA.
+		 */
+		val = val * 20;
+		break;
+	case LTC4151_VIN_H:
+		/* 25 mV per increment */
+		val = val * 25;
+		break;
+	default:
+		/* If we get here, the developer messed up */
+		WARN_ON_ONCE(1);
+		val = 0;
+		break;
+	}
+
+	return val;
+}
+
+static ssize_t ltc4151_show_value(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc4151_data *data = ltc4151_update_device(dev);
+	int value;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	value = ltc4151_get_value(data, attr->index);
+	return snprintf(buf, PAGE_SIZE, "%d\n", value);
+}
+
+/*
+ * Input voltages.
+ */
+static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, \
+	ltc4151_show_value, NULL, LTC4151_VIN_H);
+static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, \
+	ltc4151_show_value, NULL, LTC4151_ADIN_H);
+
+/* Currents (via sense resistor) */
+static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, \
+	ltc4151_show_value, NULL, LTC4151_SENSE_H);
+
+/* Finally, construct an array of pointers to members of the above objects,
+ * as required for sysfs_create_group()
+ */
+static struct attribute *ltc4151_attributes[] = {
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+
+	NULL,
+};
+
+static const struct attribute_group ltc4151_group = {
+	.attrs = ltc4151_attributes,
+};
+
+static int ltc4151_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct ltc4151_data *data;
+	int ret;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data) {
+		ret = -ENOMEM;
+		goto out_kzalloc;
+	}
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	/* Register sysfs hooks */
+	ret = sysfs_create_group(&client->dev.kobj, &ltc4151_group);
+	if (ret)
+		goto out_sysfs_create_group;
+
+	data->hwmon_dev = hwmon_device_register(&client->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		ret = PTR_ERR(data->hwmon_dev);
+		goto out_hwmon_device_register;
+	}
+
+	return 0;
+
+out_hwmon_device_register:
+	sysfs_remove_group(&client->dev.kobj, &ltc4151_group);
+out_sysfs_create_group:
+	kfree(data);
+out_kzalloc:
+	return ret;
+}
+
+static int ltc4151_remove(struct i2c_client *client)
+{
+	struct ltc4151_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &ltc4151_group);
+
+	kfree(data);
+
+	return 0;
+}
+
+static const struct i2c_device_id ltc4151_id[] = {
+	{ "ltc4151", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ltc4151_id);
+
+/* This is the driver that will be inserted */
+static struct i2c_driver ltc4151_driver = {
+	.driver = {
+		.name	= "ltc4151",
+	},
+	.probe		= ltc4151_probe,
+	.remove		= ltc4151_remove,
+	.id_table	= ltc4151_id,
+};
+
+static int __init ltc4151_init(void)
+{
+	return i2c_add_driver(&ltc4151_driver);
+}
+
+static void __exit ltc4151_exit(void)
+{
+	i2c_del_driver(&ltc4151_driver);
+}
+
+MODULE_AUTHOR("Per Dalen <per.dalen@appeartv.com>");
+MODULE_DESCRIPTION("LTC4151 driver");
+MODULE_LICENSE("GPL");
+
+module_init(ltc4151_init);
+module_exit(ltc4151_exit);