hwmon: Driver for Linear Technologies LTC4260

LTC4260 is a Positive Voltage Hot Swap Controller.
The driver currently only supports voltage monitoring, not voltage control.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

4 files changed, 269 insertions, 0 deletions

diff --git a/Documentation/hwmon/ltc4260 b/Documentation/hwmon/ltc4260
new file mode 100644
index 000000000000..c4ff4ad998b2
--- /dev/null
+++ b/Documentation/hwmon/ltc4260
@@ -0,0 +1,56 @@
+Kernel driver ltc4260
+=====================
+
+Supported chips:
+  * Linear Technology LTC4260
+    Prefix: 'ltc4260'
+    Addresses scanned: -
+    Datasheet:
+        http://cds.linear.com/docs/en/datasheet/4260fc.pdf
+
+Author: Guenter Roeck <linux@roeck-us.net>
+
+
+Description
+-----------
+
+The LTC4260 Hot Swap controller allows a board to be safely inserted
+and removed from a live backplane.
+
+
+Usage Notes
+-----------
+
+This driver does not probe for LTC4260 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 LTC4260 at address 0x10
+on I2C bus #1:
+$ modprobe ltc4260
+$ echo ltc4260 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.
+
+in1_input               SOURCE voltage (mV)
+in1_min_alarm           Undervoltage alarm
+in1_max_alarm           Overvoltage alarm
+
+in2_input               ADIN voltage (mV)
+in2_alarm               Power bad alarm
+
+curr1_input             SENSE current (mA)
+curr1_alarm             SENSE overcurrent alarm
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index ebf1131d05ea..436c611a40ca 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -821,6 +821,18 @@ config SENSORS_LTC4245
           This driver can also be built as a module. If so, the module will
           be called ltc4245.
 
+config SENSORS_LTC4260
+        tristate "Linear Technology LTC4260"
+        depends on I2C
+        select REGMAP_I2C
+        default n
+        help
+          If you say yes here you get support for Linear Technology LTC4261
+          Positive Voltage Hot Swap Controller I2C interface.
+
+          This driver can also be built as a module. If so, the module will
+          be called ltc4260.
+
 config SENSORS_LTC4261
         tristate "Linear Technology LTC4261"
         depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index f2a4048fe6ca..cdf325818af7 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -99,6 +99,7 @@ obj-$(CONFIG_SENSORS_LTC4151)	+= ltc4151.o
 obj-$(CONFIG_SENSORS_LTC4215)   += ltc4215.o
 obj-$(CONFIG_SENSORS_LTC4222)   += ltc4222.o
 obj-$(CONFIG_SENSORS_LTC4245)   += ltc4245.o
+obj-$(CONFIG_SENSORS_LTC4260)   += ltc4260.o
 obj-$(CONFIG_SENSORS_LTC4261)   += ltc4261.o
 obj-$(CONFIG_SENSORS_MAX1111)   += max1111.o
 obj-$(CONFIG_SENSORS_MAX16065)  += max16065.o
diff --git a/drivers/hwmon/ltc4260.c b/drivers/hwmon/ltc4260.c
new file mode 100644
index 000000000000..453a250d9df5
--- /dev/null
+++ b/drivers/hwmon/ltc4260.c
@@ -0,0 +1,200 @@
+/*
+ * Driver for Linear Technology LTC4260 I2C Positive Voltage Hot Swap Controller
+ *
+ * Copyright (c) 2014 Guenter Roeck
+ *
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/regmap.h>
+
+/* chip registers */
+#define LTC4260_CONTROL 0x00
+#define LTC4260_ALERT   0x01
+#define LTC4260_STATUS  0x02
+#define LTC4260_FAULT   0x03
+#define LTC4260_SENSE   0x04
+#define LTC4260_SOURCE  0x05
+#define LTC4260_ADIN    0x06
+
+/*
+ * Fault register bits
+ */
+#define FAULT_OV        (1 << 0)
+#define FAULT_UV        (1 << 1)
+#define FAULT_OC        (1 << 2)
+#define FAULT_POWER_BAD (1 << 3)
+#define FAULT_FET_SHORT (1 << 5)
+
+/* Return the voltage from the given register in mV or mA */
+static int ltc4260_get_value(struct device *dev, u8 reg)
+{
+        struct regmap *regmap = dev_get_drvdata(dev);
+        unsigned int val;
+        int ret;
+
+        ret = regmap_read(regmap, reg, &val);
+        if (ret < 0)
+                return ret;
+
+        switch (reg) {
+        case LTC4260_ADIN:
+                /* 10 mV resolution. Convert to mV. */
+                val = val * 10;
+                break;
+        case LTC4260_SOURCE:
+                /* 400 mV resolution. Convert to mV. */
+                val = val * 400;
+                break;
+        case LTC4260_SENSE:
+                /*
+                 * 300 uV 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 * 300;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        return val;
+}
+
+static ssize_t ltc4260_show_value(struct device *dev,
+                                  struct device_attribute *da, char *buf)
+{
+        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+        int value;
+
+        value = ltc4260_get_value(dev, attr->index);
+        if (value < 0)
+                return value;
+        return snprintf(buf, PAGE_SIZE, "%d\n", value);
+}
+
+static ssize_t ltc4260_show_bool(struct device *dev,
+                                 struct device_attribute *da, char *buf)
+{
+        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+        struct regmap *regmap = dev_get_drvdata(dev);
+        unsigned int fault;
+        int ret;
+
+        ret = regmap_read(regmap, LTC4260_FAULT, &fault);
+        if (ret < 0)
+                return ret;
+
+        fault &= attr->index;
+        if (fault)              /* Clear reported faults in chip register */
+                regmap_update_bits(regmap, LTC4260_FAULT, attr->index, 0);
+
+        return snprintf(buf, PAGE_SIZE, "%d\n", !!fault);
+}
+
+/* Voltages */
+static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4260_show_value, NULL,
+                          LTC4260_SOURCE);
+static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4260_show_value, NULL,
+                          LTC4260_ADIN);
+
+/*
+ * Voltage alarms
+ * UV/OV faults are associated with the input voltage, and the POWER BAD and
+ * FET SHORT faults are associated with the output voltage.
+ */
+static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4260_show_bool, NULL,
+                          FAULT_UV);
+static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4260_show_bool, NULL,
+                          FAULT_OV);
+static SENSOR_DEVICE_ATTR(in2_alarm, S_IRUGO, ltc4260_show_bool, NULL,
+                          FAULT_POWER_BAD | FAULT_FET_SHORT);
+
+/* Current (via sense resistor) */
+static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4260_show_value, NULL,
+                          LTC4260_SENSE);
+
+/* Overcurrent alarm */
+static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4260_show_bool, NULL,
+                          FAULT_OC);
+
+static struct attribute *ltc4260_attrs[] = {
+        &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_alarm.dev_attr.attr,
+
+        &sensor_dev_attr_curr1_input.dev_attr.attr,
+        &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
+
+        NULL,
+};
+ATTRIBUTE_GROUPS(ltc4260);
+
+static struct regmap_config ltc4260_regmap_config = {
+        .reg_bits = 8,
+        .val_bits = 8,
+        .max_register = LTC4260_ADIN,
+};
+
+static int ltc4260_probe(struct i2c_client *client,
+                         const struct i2c_device_id *id)
+{
+        struct device *dev = &client->dev;
+        struct device *hwmon_dev;
+        struct regmap *regmap;
+
+        regmap = devm_regmap_init_i2c(client, &ltc4260_regmap_config);
+        if (IS_ERR(regmap)) {
+                dev_err(dev, "failed to allocate register map\n");
+                return PTR_ERR(regmap);
+        }
+
+        /* Clear faults */
+        regmap_write(regmap, LTC4260_FAULT, 0x00);
+
+        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+                                                           regmap,
+                                                           ltc4260_groups);
+        return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ltc4260_id[] = {
+        {"ltc4260", 0},
+        { }
+};
+
+MODULE_DEVICE_TABLE(i2c, ltc4260_id);
+
+static struct i2c_driver ltc4260_driver = {
+        .driver = {
+                   .name = "ltc4260",
+                   },
+        .probe = ltc4260_probe,
+        .id_table = ltc4260_id,
+};
+
+module_i2c_driver(ltc4260_driver);
+
+MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
+MODULE_DESCRIPTION("LTC4260 driver");
+MODULE_LICENSE("GPL");