/* * Driver for Linear Technology LTC4215 I2C Hot Swap Controller * * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu> * * 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; version 2 of the License. * * 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 = 1; } 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_show_voltage(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 snprintf(buf, PAGE_SIZE, "%d\n", voltage); } static ssize_t ltc4215_show_current(struct device *dev, struct device_attribute *da, char *buf) { const unsigned int curr = ltc4215_get_current(dev); return snprintf(buf, PAGE_SIZE, "%u\n", curr); } static ssize_t ltc4215_show_power(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 snprintf(buf, PAGE_SIZE, "%u\n", power); } static ssize_t ltc4215_show_alarm(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 snprintf(buf, PAGE_SIZE, "%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(curr1_input, S_IRUGO, ltc4215_show_current, NULL, 0); static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 1 << 2); /* Power (virtual) */ static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ltc4215_show_power, NULL, 0); /* Input Voltage */ static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4215_show_voltage, NULL, LTC4215_ADIN); static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 1 << 0); static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 1 << 1); /* Output Voltage */ static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4215_show_voltage, NULL, LTC4215_SOURCE); static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 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, const struct i2c_device_id *id) { 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 = 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");