1 files changed, 266 insertions, 0 deletions
diff --git a/drivers/hwmon/ltc4215.c b/drivers/hwmon/ltc4215.c
new file mode 100644
index 000000000..fa43d26dd
--- /dev/null
+++ b/drivers/hwmon/ltc4215.c
@@ -0,0 +1,266 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Linear Technology LTC4215 I2C Hot Swap Controller
+ *
+ * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
+ *
+ * Datasheet:
+ * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697
+ */
+
+#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>
+#include <linux/jiffies.h>
+
+/* Here are names of the chip's registers (a.k.a. commands) */
+enum ltc4215_cmd {
+	LTC4215_CONTROL			= 0x00, /* rw */
+	LTC4215_ALERT			= 0x01, /* rw */
+	LTC4215_STATUS			= 0x02, /* ro */
+	LTC4215_FAULT			= 0x03, /* rw */
+	LTC4215_SENSE			= 0x04, /* rw */
+	LTC4215_SOURCE			= 0x05, /* rw */
+	LTC4215_ADIN			= 0x06, /* rw */
+};
+
+struct ltc4215_data {
+	struct i2c_client *client;
+
+	struct mutex update_lock;
+	bool valid;
+	unsigned long last_updated; /* in jiffies */
+
+	/* Registers */
+	u8 regs[7];
+};
+
+static struct ltc4215_data *ltc4215_update_device(struct device *dev)
+{
+	struct ltc4215_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	s32 val;
+	int i;
+
+	mutex_lock(&data->update_lock);
+
+	/* The chip's A/D updates 10 times per second */
+	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
+
+		dev_dbg(&client->dev, "Starting ltc4215 update\n");
+
+		/* Read all registers */
+		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
+			val = i2c_smbus_read_byte_data(client, i);
+			if (unlikely(val < 0))
+				data->regs[i] = 0;
+			else
+				data->regs[i] = val;
+		}
+
+		data->last_updated = jiffies;
+		data->valid = true;
+	}
+
+	mutex_unlock(&data->update_lock);
+
+	return data;
+}
+
+/* Return the voltage from the given register in millivolts */
+static int ltc4215_get_voltage(struct device *dev, u8 reg)
+{
+	struct ltc4215_data *data = ltc4215_update_device(dev);
+	const u8 regval = data->regs[reg];
+	u32 voltage = 0;
+
+	switch (reg) {
+	case LTC4215_SENSE:
+		/* 151 uV per increment */
+		voltage = regval * 151 / 1000;
+		break;
+	case LTC4215_SOURCE:
+		/* 60.5 mV per increment */
+		voltage = regval * 605 / 10;
+		break;
+	case LTC4215_ADIN:
+		/*
+		 * The ADIN input is divided by 12.5, and has 4.82 mV
+		 * per increment, so we have the additional multiply
+		 */
+		voltage = regval * 482 * 125 / 1000;
+		break;
+	default:
+		/* If we get here, the developer messed up */
+		WARN_ON_ONCE(1);
+		break;
+	}
+
+	return voltage;
+}
+
+/* Return the current from the sense resistor in mA */
+static unsigned int ltc4215_get_current(struct device *dev)
+{
+	struct ltc4215_data *data = ltc4215_update_device(dev);
+
+	/*
+	 * The strange looking conversions that follow are fixed-point
+	 * math, since we cannot do floating point in the kernel.
+	 *
+	 * Step 1: convert sense register to microVolts
+	 * Step 2: convert voltage to milliAmperes
+	 *
+	 * If you play around with the V=IR equation, you come up with
+	 * the following: X uV / Y mOhm == Z mA
+	 *
+	 * With the resistors that are fractions of a milliOhm, we multiply
+	 * the voltage and resistance by 10, to shift the decimal point.
+	 * Now we can use the normal division operator again.
+	 */
+
+	/* Calculate voltage in microVolts (151 uV per increment) */
+	const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
+
+	/* Calculate current in milliAmperes (4 milliOhm sense resistor) */
+	const unsigned int curr = voltage / 4;
+
+	return curr;
+}
+
+static ssize_t ltc4215_voltage_show(struct device *dev,
+				    struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	const int voltage = ltc4215_get_voltage(dev, attr->index);
+
+	return sysfs_emit(buf, "%d\n", voltage);
+}
+
+static ssize_t ltc4215_current_show(struct device *dev,
+				    struct device_attribute *da, char *buf)
+{
+	const unsigned int curr = ltc4215_get_current(dev);
+
+	return sysfs_emit(buf, "%u\n", curr);
+}
+
+static ssize_t ltc4215_power_show(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	const unsigned int curr = ltc4215_get_current(dev);
+	const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
+
+	/* current in mA * voltage in mV == power in uW */
+	const unsigned int power = abs(output_voltage * curr);
+
+	return sysfs_emit(buf, "%u\n", power);
+}
+
+static ssize_t ltc4215_alarm_show(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc4215_data *data = ltc4215_update_device(dev);
+	const u8 reg = data->regs[LTC4215_STATUS];
+	const u32 mask = attr->index;
+
+	return sysfs_emit(buf, "%u\n", !!(reg & mask));
+}
+
+/*
+ * 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.
+ */
+
+/* Construct a sensor_device_attribute structure for each register */
+
+/* Current */
+static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4215_current, 0);
+static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4215_alarm, 1 << 2);
+
+/* Power (virtual) */
+static SENSOR_DEVICE_ATTR_RO(power1_input, ltc4215_power, 0);
+
+/* Input Voltage */
+static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4215_voltage, LTC4215_ADIN);
+static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4215_alarm, 1 << 0);
+static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4215_alarm, 1 << 1);
+
+/* Output Voltage */
+static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4215_voltage, LTC4215_SOURCE);
+static SENSOR_DEVICE_ATTR_RO(in2_min_alarm, ltc4215_alarm, 1 << 3);
+
+/*
+ * Finally, construct an array of pointers to members of the above objects,
+ * as required for sysfs_create_group()
+ */
+static struct attribute *ltc4215_attrs[] = {
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_power1_input.dev_attr.attr,
+
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
+
+	NULL,
+};
+ATTRIBUTE_GROUPS(ltc4215);
+
+static int ltc4215_probe(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct device *dev = &client->dev;
+	struct ltc4215_data *data;
+	struct device *hwmon_dev;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	mutex_init(&data->update_lock);
+
+	/* Initialize the LTC4215 chip */
+	i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+							   data,
+							   ltc4215_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ltc4215_id[] = {
+	{ "ltc4215", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ltc4215_id);
+
+/* This is the driver that will be inserted */
+static struct i2c_driver ltc4215_driver = {
+	.driver = {
+		.name	= "ltc4215",
+	},
+	.probe_new	= ltc4215_probe,
+	.id_table	= ltc4215_id,
+};
+
+module_i2c_driver(ltc4215_driver);
+
+MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
+MODULE_DESCRIPTION("LTC4215 driver");
+MODULE_LICENSE("GPL");