linux/drivers/hwmon/ltc4215.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller
   4 *
   5 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu>
   6 *
   7 * Datasheet:
   8 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697
   9 */
  10
  11#include <linux/kernel.h>
  12#include <linux/module.h>
  13#include <linux/init.h>
  14#include <linux/err.h>
  15#include <linux/slab.h>
  16#include <linux/i2c.h>
  17#include <linux/hwmon.h>
  18#include <linux/hwmon-sysfs.h>
  19#include <linux/jiffies.h>
  20
  21/* Here are names of the chip's registers (a.k.a. commands) */
  22enum ltc4215_cmd {
  23        LTC4215_CONTROL                 = 0x00, /* rw */
  24        LTC4215_ALERT                   = 0x01, /* rw */
  25        LTC4215_STATUS                  = 0x02, /* ro */
  26        LTC4215_FAULT                   = 0x03, /* rw */
  27        LTC4215_SENSE                   = 0x04, /* rw */
  28        LTC4215_SOURCE                  = 0x05, /* rw */
  29        LTC4215_ADIN                    = 0x06, /* rw */
  30};
  31
  32struct ltc4215_data {
  33        struct i2c_client *client;
  34
  35        struct mutex update_lock;
  36        bool valid;
  37        unsigned long last_updated; /* in jiffies */
  38
  39        /* Registers */
  40        u8 regs[7];
  41};
  42
  43static struct ltc4215_data *ltc4215_update_device(struct device *dev)
  44{
  45        struct ltc4215_data *data = dev_get_drvdata(dev);
  46        struct i2c_client *client = data->client;
  47        s32 val;
  48        int i;
  49
  50        mutex_lock(&data->update_lock);
  51
  52        /* The chip's A/D updates 10 times per second */
  53        if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
  54
  55                dev_dbg(&client->dev, "Starting ltc4215 update\n");
  56
  57                /* Read all registers */
  58                for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
  59                        val = i2c_smbus_read_byte_data(client, i);
  60                        if (unlikely(val < 0))
  61                                data->regs[i] = 0;
  62                        else
  63                                data->regs[i] = val;
  64                }
  65
  66                data->last_updated = jiffies;
  67                data->valid = 1;
  68        }
  69
  70        mutex_unlock(&data->update_lock);
  71
  72        return data;
  73}
  74
  75/* Return the voltage from the given register in millivolts */
  76static int ltc4215_get_voltage(struct device *dev, u8 reg)
  77{
  78        struct ltc4215_data *data = ltc4215_update_device(dev);
  79        const u8 regval = data->regs[reg];
  80        u32 voltage = 0;
  81
  82        switch (reg) {
  83        case LTC4215_SENSE:
  84                /* 151 uV per increment */
  85                voltage = regval * 151 / 1000;
  86                break;
  87        case LTC4215_SOURCE:
  88                /* 60.5 mV per increment */
  89                voltage = regval * 605 / 10;
  90                break;
  91        case LTC4215_ADIN:
  92                /*
  93                 * The ADIN input is divided by 12.5, and has 4.82 mV
  94                 * per increment, so we have the additional multiply
  95                 */
  96                voltage = regval * 482 * 125 / 1000;
  97                break;
  98        default:
  99                /* If we get here, the developer messed up */
 100                WARN_ON_ONCE(1);
 101                break;
 102        }
 103
 104        return voltage;
 105}
 106
 107/* Return the current from the sense resistor in mA */
 108static unsigned int ltc4215_get_current(struct device *dev)
 109{
 110        struct ltc4215_data *data = ltc4215_update_device(dev);
 111
 112        /*
 113         * The strange looking conversions that follow are fixed-point
 114         * math, since we cannot do floating point in the kernel.
 115         *
 116         * Step 1: convert sense register to microVolts
 117         * Step 2: convert voltage to milliAmperes
 118         *
 119         * If you play around with the V=IR equation, you come up with
 120         * the following: X uV / Y mOhm == Z mA
 121         *
 122         * With the resistors that are fractions of a milliOhm, we multiply
 123         * the voltage and resistance by 10, to shift the decimal point.
 124         * Now we can use the normal division operator again.
 125         */
 126
 127        /* Calculate voltage in microVolts (151 uV per increment) */
 128        const unsigned int voltage = data->regs[LTC4215_SENSE] * 151;
 129
 130        /* Calculate current in milliAmperes (4 milliOhm sense resistor) */
 131        const unsigned int curr = voltage / 4;
 132
 133        return curr;
 134}
 135
 136static ssize_t ltc4215_voltage_show(struct device *dev,
 137                                    struct device_attribute *da, char *buf)
 138{
 139        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 140        const int voltage = ltc4215_get_voltage(dev, attr->index);
 141
 142        return sysfs_emit(buf, "%d\n", voltage);
 143}
 144
 145static ssize_t ltc4215_current_show(struct device *dev,
 146                                    struct device_attribute *da, char *buf)
 147{
 148        const unsigned int curr = ltc4215_get_current(dev);
 149
 150        return sysfs_emit(buf, "%u\n", curr);
 151}
 152
 153static ssize_t ltc4215_power_show(struct device *dev,
 154                                  struct device_attribute *da, char *buf)
 155{
 156        const unsigned int curr = ltc4215_get_current(dev);
 157        const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN);
 158
 159        /* current in mA * voltage in mV == power in uW */
 160        const unsigned int power = abs(output_voltage * curr);
 161
 162        return sysfs_emit(buf, "%u\n", power);
 163}
 164
 165static ssize_t ltc4215_alarm_show(struct device *dev,
 166                                  struct device_attribute *da, char *buf)
 167{
 168        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 169        struct ltc4215_data *data = ltc4215_update_device(dev);
 170        const u8 reg = data->regs[LTC4215_STATUS];
 171        const u32 mask = attr->index;
 172
 173        return sysfs_emit(buf, "%u\n", !!(reg & mask));
 174}
 175
 176/*
 177 * These macros are used below in constructing device attribute objects
 178 * for use with sysfs_create_group() to make a sysfs device file
 179 * for each register.
 180 */
 181
 182/* Construct a sensor_device_attribute structure for each register */
 183
 184/* Current */
 185static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4215_current, 0);
 186static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4215_alarm, 1 << 2);
 187
 188/* Power (virtual) */
 189static SENSOR_DEVICE_ATTR_RO(power1_input, ltc4215_power, 0);
 190
 191/* Input Voltage */
 192static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4215_voltage, LTC4215_ADIN);
 193static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4215_alarm, 1 << 0);
 194static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4215_alarm, 1 << 1);
 195
 196/* Output Voltage */
 197static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4215_voltage, LTC4215_SOURCE);
 198static SENSOR_DEVICE_ATTR_RO(in2_min_alarm, ltc4215_alarm, 1 << 3);
 199
 200/*
 201 * Finally, construct an array of pointers to members of the above objects,
 202 * as required for sysfs_create_group()
 203 */
 204static struct attribute *ltc4215_attrs[] = {
 205        &sensor_dev_attr_curr1_input.dev_attr.attr,
 206        &sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 207
 208        &sensor_dev_attr_power1_input.dev_attr.attr,
 209
 210        &sensor_dev_attr_in1_input.dev_attr.attr,
 211        &sensor_dev_attr_in1_max_alarm.dev_attr.attr,
 212        &sensor_dev_attr_in1_min_alarm.dev_attr.attr,
 213
 214        &sensor_dev_attr_in2_input.dev_attr.attr,
 215        &sensor_dev_attr_in2_min_alarm.dev_attr.attr,
 216
 217        NULL,
 218};
 219ATTRIBUTE_GROUPS(ltc4215);
 220
 221static int ltc4215_probe(struct i2c_client *client)
 222{
 223        struct i2c_adapter *adapter = client->adapter;
 224        struct device *dev = &client->dev;
 225        struct ltc4215_data *data;
 226        struct device *hwmon_dev;
 227
 228        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 229                return -ENODEV;
 230
 231        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 232        if (!data)
 233                return -ENOMEM;
 234
 235        data->client = client;
 236        mutex_init(&data->update_lock);
 237
 238        /* Initialize the LTC4215 chip */
 239        i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00);
 240
 241        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
 242                                                           data,
 243                                                           ltc4215_groups);
 244        return PTR_ERR_OR_ZERO(hwmon_dev);
 245}
 246
 247static const struct i2c_device_id ltc4215_id[] = {
 248        { "ltc4215", 0 },
 249        { }
 250};
 251MODULE_DEVICE_TABLE(i2c, ltc4215_id);
 252
 253/* This is the driver that will be inserted */
 254static struct i2c_driver ltc4215_driver = {
 255        .driver = {
 256                .name   = "ltc4215",
 257        },
 258        .probe_new      = ltc4215_probe,
 259        .id_table       = ltc4215_id,
 260};
 261
 262module_i2c_driver(ltc4215_driver);
 263
 264MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 265MODULE_DESCRIPTION("LTC4215 driver");
 266MODULE_LICENSE("GPL");
 267