328 lines
8.3 KiB
C
328 lines
8.3 KiB
C
/*
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* Driver for Linear Technology LTC4215 I2C Hot Swap Controller
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*
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* Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* Datasheet:
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* http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/i2c.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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/* Here are names of the chip's registers (a.k.a. commands) */
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enum ltc4215_cmd {
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LTC4215_CONTROL = 0x00, /* rw */
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LTC4215_ALERT = 0x01, /* rw */
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LTC4215_STATUS = 0x02, /* ro */
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LTC4215_FAULT = 0x03, /* rw */
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LTC4215_SENSE = 0x04, /* rw */
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LTC4215_SOURCE = 0x05, /* rw */
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LTC4215_ADIN = 0x06, /* rw */
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};
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struct ltc4215_data {
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struct device *hwmon_dev;
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struct mutex update_lock;
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bool valid;
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unsigned long last_updated; /* in jiffies */
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/* Registers */
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u8 regs[7];
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};
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static struct ltc4215_data *ltc4215_update_device(struct device *dev)
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{
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struct i2c_client *client = to_i2c_client(dev);
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struct ltc4215_data *data = i2c_get_clientdata(client);
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s32 val;
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int i;
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mutex_lock(&data->update_lock);
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/* The chip's A/D updates 10 times per second */
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if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
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dev_dbg(&client->dev, "Starting ltc4215 update\n");
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/* Read all registers */
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for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
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val = i2c_smbus_read_byte_data(client, i);
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if (unlikely(val < 0))
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data->regs[i] = 0;
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else
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data->regs[i] = val;
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}
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data->last_updated = jiffies;
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data->valid = 1;
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}
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mutex_unlock(&data->update_lock);
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return data;
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}
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/* Return the voltage from the given register in millivolts */
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static int ltc4215_get_voltage(struct device *dev, u8 reg)
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{
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struct ltc4215_data *data = ltc4215_update_device(dev);
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const u8 regval = data->regs[reg];
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u32 voltage = 0;
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switch (reg) {
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case LTC4215_SENSE:
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/* 151 uV per increment */
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voltage = regval * 151 / 1000;
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break;
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case LTC4215_SOURCE:
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/* 60.5 mV per increment */
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voltage = regval * 605 / 10;
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break;
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case LTC4215_ADIN:
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/* The ADIN input is divided by 12.5, and has 4.82 mV
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* per increment, so we have the additional multiply */
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voltage = regval * 482 * 125 / 1000;
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break;
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default:
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/* If we get here, the developer messed up */
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WARN_ON_ONCE(1);
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break;
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}
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return voltage;
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}
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/* Return the current from the sense resistor in mA */
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static unsigned int ltc4215_get_current(struct device *dev)
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{
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struct ltc4215_data *data = ltc4215_update_device(dev);
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/* The strange looking conversions that follow are fixed-point
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* math, since we cannot do floating point in the kernel.
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*
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* Step 1: convert sense register to microVolts
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* Step 2: convert voltage to milliAmperes
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*
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* If you play around with the V=IR equation, you come up with
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* the following: X uV / Y mOhm == Z mA
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*
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* With the resistors that are fractions of a milliOhm, we multiply
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* the voltage and resistance by 10, to shift the decimal point.
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* Now we can use the normal division operator again.
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*/
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/* Calculate voltage in microVolts (151 uV per increment) */
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const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
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/* Calculate current in milliAmperes (4 milliOhm sense resistor) */
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const unsigned int curr = voltage / 4;
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return curr;
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}
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static ssize_t ltc4215_show_voltage(struct device *dev,
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struct device_attribute *da,
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char *buf)
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{
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struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
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const int voltage = ltc4215_get_voltage(dev, attr->index);
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return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
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}
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static ssize_t ltc4215_show_current(struct device *dev,
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struct device_attribute *da,
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char *buf)
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{
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const unsigned int curr = ltc4215_get_current(dev);
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return snprintf(buf, PAGE_SIZE, "%u\n", curr);
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}
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static ssize_t ltc4215_show_power(struct device *dev,
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struct device_attribute *da,
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char *buf)
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{
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const unsigned int curr = ltc4215_get_current(dev);
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const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
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/* current in mA * voltage in mV == power in uW */
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const unsigned int power = abs(output_voltage * curr);
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return snprintf(buf, PAGE_SIZE, "%u\n", power);
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}
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static ssize_t ltc4215_show_alarm(struct device *dev,
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struct device_attribute *da,
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char *buf)
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{
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struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
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struct ltc4215_data *data = ltc4215_update_device(dev);
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const u8 reg = data->regs[attr->index];
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const u32 mask = attr->nr;
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return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
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}
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/* These macros are used below in constructing device attribute objects
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* for use with sysfs_create_group() to make a sysfs device file
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* for each register.
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*/
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#define LTC4215_VOLTAGE(name, ltc4215_cmd_idx) \
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static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
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ltc4215_show_voltage, NULL, ltc4215_cmd_idx)
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#define LTC4215_CURRENT(name) \
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static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
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ltc4215_show_current, NULL, 0);
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#define LTC4215_POWER(name) \
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static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
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ltc4215_show_power, NULL, 0);
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#define LTC4215_ALARM(name, mask, reg) \
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static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
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ltc4215_show_alarm, NULL, (mask), reg)
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/* Construct a sensor_device_attribute structure for each register */
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/* Current */
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LTC4215_CURRENT(curr1_input);
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LTC4215_ALARM(curr1_max_alarm, (1 << 2), LTC4215_STATUS);
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/* Power (virtual) */
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LTC4215_POWER(power1_input);
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LTC4215_ALARM(power1_alarm, (1 << 3), LTC4215_STATUS);
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/* Input Voltage */
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LTC4215_VOLTAGE(in1_input, LTC4215_ADIN);
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LTC4215_ALARM(in1_max_alarm, (1 << 0), LTC4215_STATUS);
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LTC4215_ALARM(in1_min_alarm, (1 << 1), LTC4215_STATUS);
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/* Output Voltage */
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LTC4215_VOLTAGE(in2_input, LTC4215_SOURCE);
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/* Finally, construct an array of pointers to members of the above objects,
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* as required for sysfs_create_group()
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*/
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static struct attribute *ltc4215_attributes[] = {
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&sensor_dev_attr_curr1_input.dev_attr.attr,
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&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
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&sensor_dev_attr_power1_input.dev_attr.attr,
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&sensor_dev_attr_power1_alarm.dev_attr.attr,
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&sensor_dev_attr_in1_input.dev_attr.attr,
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&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
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&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
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&sensor_dev_attr_in2_input.dev_attr.attr,
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NULL,
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};
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static const struct attribute_group ltc4215_group = {
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.attrs = ltc4215_attributes,
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};
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static int ltc4215_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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struct i2c_adapter *adapter = client->adapter;
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struct ltc4215_data *data;
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int ret;
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if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
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return -ENODEV;
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data = kzalloc(sizeof(*data), GFP_KERNEL);
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if (!data) {
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ret = -ENOMEM;
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goto out_kzalloc;
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}
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i2c_set_clientdata(client, data);
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mutex_init(&data->update_lock);
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/* Initialize the LTC4215 chip */
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i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
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/* Register sysfs hooks */
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ret = sysfs_create_group(&client->dev.kobj, <c4215_group);
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if (ret)
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goto out_sysfs_create_group;
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data->hwmon_dev = hwmon_device_register(&client->dev);
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if (IS_ERR(data->hwmon_dev)) {
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ret = PTR_ERR(data->hwmon_dev);
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goto out_hwmon_device_register;
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}
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return 0;
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out_hwmon_device_register:
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sysfs_remove_group(&client->dev.kobj, <c4215_group);
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out_sysfs_create_group:
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kfree(data);
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out_kzalloc:
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return ret;
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}
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static int ltc4215_remove(struct i2c_client *client)
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{
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struct ltc4215_data *data = i2c_get_clientdata(client);
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hwmon_device_unregister(data->hwmon_dev);
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sysfs_remove_group(&client->dev.kobj, <c4215_group);
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kfree(data);
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return 0;
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}
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static const struct i2c_device_id ltc4215_id[] = {
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{ "ltc4215", 0 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, ltc4215_id);
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/* This is the driver that will be inserted */
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static struct i2c_driver ltc4215_driver = {
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.driver = {
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.name = "ltc4215",
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},
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.probe = ltc4215_probe,
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.remove = ltc4215_remove,
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.id_table = ltc4215_id,
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};
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static int __init ltc4215_init(void)
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{
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return i2c_add_driver(<c4215_driver);
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}
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static void __exit ltc4215_exit(void)
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{
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i2c_del_driver(<c4215_driver);
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}
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MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
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MODULE_DESCRIPTION("LTC4215 driver");
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MODULE_LICENSE("GPL");
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module_init(ltc4215_init);
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module_exit(ltc4215_exit);
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