drivers/hwmon/ltc4215.c

   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) */
  22 enum 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
  32 struct 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
  43 static 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 */
  76 static 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 */
 108 static 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
 136 static 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 snprintf(buf, PAGE_SIZE, "%d\n", voltage);
 143 }
 144
 145 static 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 snprintf(buf, PAGE_SIZE, "%u\n", curr);
 151 }
 152
 153 static 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 snprintf(buf, PAGE_SIZE, "%u\n", power);
 163 }
 164
 165 static 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 snprintf(buf, PAGE_SIZE, "%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 */
 185 static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4215_current, 0);
 186 static SENSOR_DEVICE_ATTR_RO(curr1_max_alarm, ltc4215_alarm, 1 << 2);
 187
 188 /* Power (virtual) */
 189 static SENSOR_DEVICE_ATTR_RO(power1_input, ltc4215_power, 0);
 190
 191 /* Input Voltage */
 192 static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4215_voltage, LTC4215_ADIN);
 193 static SENSOR_DEVICE_ATTR_RO(in1_max_alarm, ltc4215_alarm, 1 << 0);
 194 static SENSOR_DEVICE_ATTR_RO(in1_min_alarm, ltc4215_alarm, 1 << 1);
 195
 196 /* Output Voltage */
 197 static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4215_voltage, LTC4215_SOURCE);
 198 static 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  */
 204 static 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 };
 219 ATTRIBUTE_GROUPS(ltc4215);
 220
 221 static 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
 247 static const struct i2c_device_id ltc4215_id[] = {
 248         { "ltc4215", 0 },
 249         { }
 250 };
 251 MODULE_DEVICE_TABLE(i2c, ltc4215_id);
 252
 253 /* This is the driver that will be inserted */
 254 static struct i2c_driver ltc4215_driver = {
 255         .driver = {
 256                 .name   = "ltc4215",
 257         },
 258         .probe_new      = ltc4215_probe,
 259         .id_table       = ltc4215_id,
 260 };
 261
 262 module_i2c_driver(ltc4215_driver);
 263
 264 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 265 MODULE_DESCRIPTION("LTC4215 driver");
 266 MODULE_LICENSE("GPL");