hwmon: LTC4261 Hardware monitoring driver

This driver adds support for Linear Technology LTC4261 I2C Negative
Voltage Hot Swap Controller.

Reviewed-by: Ira W. Snyder <iws@ovro.caltech.edu>
Reviewed-by: Tom Grennan <tom.grennan@ericsson.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>

5 files changed, 397 insertions, 0 deletions

diff --git a/Documentation/hwmon/ltc4261 b/Documentation/hwmon/ltc4261
new file mode 100644
index 000000000000..eba2e2c4b94d
--- /dev/null
+++ b/Documentation/hwmon/ltc4261
@@ -0,0 +1,63 @@
+Kernel driver ltc4261
+=====================
+
+Supported chips:
+  * Linear Technology LTC4261
+    Prefix: 'ltc4261'
+    Addresses scanned: -
+    Datasheet:
+        http://cds.linear.com/docs/Datasheet/42612fb.pdf
+
+Author: Guenter Roeck <guenter.roeck@ericsson.com>
+
+
+Description
+-----------
+
+The LTC4261/LTC4261-2 negative voltage Hot Swap controllers allow a board
+to be safely inserted and removed from a live backplane.
+
+
+Usage Notes
+-----------
+
+This driver does not probe for LTC4261 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 LTC4261 at address 0x10
+on I2C bus #1:
+$ modprobe ltc4261
+$ echo ltc4261 0x10 > /sys/bus/i2c/devices/i2c-1/new_device
+
+
+Sysfs entries
+-------------
+
+Voltage readings provided by this driver are reported as obtained from the ADC
+registers. If a set of voltage divider resistors is installed, calculate the
+real voltage by multiplying the reported value with (R1+R2)/R2, where R1 is the
+value of the divider resistor against the measured voltage and R2 is the value
+of the divider resistor against Ground.
+
+Current reading provided by this driver is reported as obtained from the ADC
+Current Sense register. The reported value assumes that a 1 mOhm sense resistor
+is installed. If a different sense resistor is installed, calculate the real
+current by dividing the reported value by the sense resistor value in mOhm.
+
+The chip has two voltage sensors, but only one set of voltage alarm status bits.
+In many many designs, those alarms are associated with the ADIN2 sensor, due to
+the proximity of the ADIN2 pin to the OV pin. ADIN2 is, however, not available
+on all chip variants. To ensure that the alarm condition is reported to the user,
+report it with both voltage sensors.
+
+in1_input		ADIN2 voltage (mV)
+in1_min_alarm		ADIN/ADIN2 Undervoltage alarm
+in1_max_alarm		ADIN/ADIN2 Overvoltage alarm
+
+in2_input		ADIN voltage (mV)
+in2_min_alarm		ADIN/ADIN2 Undervoltage alarm
+in2_max_alarm		ADIN/ADIN2 Overvoltage alarm
+
+curr1_input		SENSE current (mA)
+curr1_alarm		SENSE overcurrent alarm
diff --git a/MAINTAINERS b/MAINTAINERS
index 541451050b36..146b8a068a4e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3765,6 +3765,13 @@ L:	linux-scsi@vger.kernel.org
 S:	Maintained
 F:	drivers/scsi/sym53c8xx_2/
 
+LTC4261 HARDWARE MONITOR DRIVER
+M:	Guenter Roeck <linux@roeck-us.net>
+L:	lm-sensors@lm-sensors.org
+S:	Maintained
+F:	Documentation/hwmon/ltc4261
+F:	drivers/hwmon/ltc4261.c
+
 LTP (Linux Test Project)
 M:	Rishikesh K Rajak <risrajak@linux.vnet.ibm.com>
 M:	Garrett Cooper <yanegomi@gmail.com>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index e382da3122b7..ec4295fd22f6 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -654,6 +654,17 @@ config SENSORS_LTC4245
 	  This driver can also be built as a module. If so, the module will
 	  be called ltc4245.
 
+config SENSORS_LTC4261
+	tristate "Linear Technology LTC4261"
+	depends on I2C && EXPERIMENTAL
+	default n
+	help
+	  If you say yes here you get support for Linear Technology LTC4261
+	  Negative Voltage Hot Swap Controller I2C interface.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called ltc4261.
+
 config SENSORS_LM95241
 	tristate "National Semiconductor LM95241 sensor chip"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index ec9cb735c898..fc38e7c131f8 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -79,6 +79,7 @@ obj-$(CONFIG_SENSORS_LM93)	+= lm93.o
 obj-$(CONFIG_SENSORS_LM95241)	+= lm95241.o
 obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o
 obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o
+obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
 obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
 obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
 obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
diff --git a/drivers/hwmon/ltc4261.c b/drivers/hwmon/ltc4261.c
new file mode 100644
index 000000000000..267626178678
--- /dev/null
+++ b/drivers/hwmon/ltc4261.c
@@ -0,0 +1,315 @@
+/*
+ * Driver for Linear Technology LTC4261 I2C Negative Voltage Hot Swap Controller
+ *
+ * Copyright (C) 2010 Ericsson AB.
+ *
+ * Derived from:
+ *
+ *  Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
+ *  Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
+ *
+ * Datasheet: http://cds.linear.com/docs/Datasheet/42612fb.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 LTC4261_STATUS	0x00	/* readonly */
+#define LTC4261_FAULT	0x01
+#define LTC4261_ALERT	0x02
+#define LTC4261_CONTROL	0x03
+#define LTC4261_SENSE_H	0x04
+#define LTC4261_SENSE_L	0x05
+#define LTC4261_ADIN2_H	0x06
+#define LTC4261_ADIN2_L	0x07
+#define LTC4261_ADIN_H	0x08
+#define LTC4261_ADIN_L	0x09
+
+/*
+ * Fault register bits
+ */
+#define FAULT_OV	(1<<0)
+#define FAULT_UV	(1<<1)
+#define FAULT_OC	(1<<2)
+
+struct ltc4261_data {
+	struct device *hwmon_dev;
+
+	struct mutex update_lock;
+	bool valid;
+	unsigned long last_updated;	/* in jiffies */
+
+	/* Registers */
+	u8 regs[10];
+};
+
+static struct ltc4261_data *ltc4261_update_device(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ltc4261_data *data = i2c_get_clientdata(client);
+	struct ltc4261_data *ret = data;
+
+	mutex_lock(&data->update_lock);
+
+	if (time_after(jiffies, data->last_updated + HZ / 4) || !data->valid) {
+		int i;
+
+		/* Read registers -- 0x00 to 0x09 */
+		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",
+					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 or mA */
+static int ltc4261_get_value(struct ltc4261_data *data, u8 reg)
+{
+	u32 val;
+
+	val = (data->regs[reg] << 2) + (data->regs[reg + 1] >> 6);
+
+	switch (reg) {
+	case LTC4261_ADIN_H:
+	case LTC4261_ADIN2_H:
+		/* 2.5mV resolution. Convert to mV. */
+		val = val * 25 / 10;
+		break;
+	case LTC4261_SENSE_H:
+		/*
+		 * 62.5uV resolution. Convert to current as measured with
+		 * an 1 mOhm sense resistor, in mA. If a different sense
+		 * resistor is installed, calculate the actual current by
+		 * dividing the reported current by the sense resistor value
+		 * in mOhm.
+		 */
+		val = val * 625 / 10;
+		break;
+	default:
+		/* If we get here, the developer messed up */
+		WARN_ON_ONCE(1);
+		val = 0;
+		break;
+	}
+
+	return val;
+}
+
+static ssize_t ltc4261_show_value(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc4261_data *data = ltc4261_update_device(dev);
+	int value;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	value = ltc4261_get_value(data, attr->index);
+	return snprintf(buf, PAGE_SIZE, "%d\n", value);
+}
+
+static ssize_t ltc4261_show_bool(struct device *dev,
+				 struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ltc4261_data *data = ltc4261_update_device(dev);
+	u8 fault;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	fault = data->regs[LTC4261_FAULT] & attr->index;
+	if (fault)		/* Clear reported faults in chip register */
+		i2c_smbus_write_byte_data(client, LTC4261_FAULT, ~fault);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", fault ? 1 : 0);
+}
+
+/*
+ * These macros are used below in constructing device attribute objects
+ * for use with sysfs_create_group() to make a sysfs device file
+ * for each register.
+ */
+
+#define LTC4261_VALUE(name, ltc4261_cmd_idx) \
+	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
+	ltc4261_show_value, NULL, ltc4261_cmd_idx)
+
+#define LTC4261_BOOL(name, mask) \
+	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
+	ltc4261_show_bool, NULL, (mask))
+
+/*
+ * Input voltages.
+ */
+LTC4261_VALUE(in1_input, LTC4261_ADIN_H);
+LTC4261_VALUE(in2_input, LTC4261_ADIN2_H);
+
+/*
+ * Voltage alarms. The chip has only one set of voltage alarm status bits,
+ * triggered by input voltage alarms. In many designs, those alarms are
+ * associated with the ADIN2 sensor, due to the proximity of the ADIN2 pin
+ * to the OV pin. ADIN2 is, however, not available on all chip variants.
+ * To ensure that the alarm condition is reported to the user, report it
+ * with both voltage sensors.
+ */
+LTC4261_BOOL(in1_min_alarm, FAULT_UV);
+LTC4261_BOOL(in1_max_alarm, FAULT_OV);
+LTC4261_BOOL(in2_min_alarm, FAULT_UV);
+LTC4261_BOOL(in2_max_alarm, FAULT_OV);
+
+/* Currents (via sense resistor) */
+LTC4261_VALUE(curr1_input, LTC4261_SENSE_H);
+
+/* Overcurrent alarm */
+LTC4261_BOOL(curr1_max_alarm, FAULT_OC);
+
+static struct attribute *ltc4261_attributes[] = {
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_in2_max_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
+
+	NULL,
+};
+
+static const struct attribute_group ltc4261_group = {
+	.attrs = ltc4261_attributes,
+};
+
+static int ltc4261_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct ltc4261_data *data;
+	int ret;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	if (i2c_smbus_read_byte_data(client, LTC4261_STATUS) < 0) {
+		dev_err(&client->dev, "Failed to read register %d:%02x:%02x\n",
+			adapter->id, client->addr, LTC4261_STATUS);
+		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);
+
+	/* Clear faults */
+	i2c_smbus_write_byte_data(client, LTC4261_FAULT, 0x00);
+
+	/* Register sysfs hooks */
+	ret = sysfs_create_group(&client->dev.kobj, &ltc4261_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, &ltc4261_group);
+out_sysfs_create_group:
+	kfree(data);
+out_kzalloc:
+	return ret;
+}
+
+static int ltc4261_remove(struct i2c_client *client)
+{
+	struct ltc4261_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &ltc4261_group);
+
+	kfree(data);
+
+	return 0;
+}
+
+static const struct i2c_device_id ltc4261_id[] = {
+	{"ltc4261", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, ltc4261_id);
+
+/* This is the driver that will be inserted */
+static struct i2c_driver ltc4261_driver = {
+	.driver = {
+		   .name = "ltc4261",
+		   },
+	.probe = ltc4261_probe,
+	.remove = ltc4261_remove,
+	.id_table = ltc4261_id,
+};
+
+static int __init ltc4261_init(void)
+{
+	return i2c_add_driver(&ltc4261_driver);
+}
+
+static void __exit ltc4261_exit(void)
+{
+	i2c_del_driver(&ltc4261_driver);
+}
+
+MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
+MODULE_DESCRIPTION("LTC4261 driver");
+MODULE_LICENSE("GPL");
+
+module_init(ltc4261_init);
+module_exit(ltc4261_exit);