1 /* 2 * Driver for Linear Technology LTC4215 I2C Hot Swap Controller 3 * 4 * Copyright (C) 2009 Ira W. Snyder <iws@ovro.caltech.edu> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; version 2 of the License. 9 * 10 * Datasheet: 11 * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1163,P17572,D12697 12 */ 13 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/init.h> 17 #include <linux/err.h> 18 #include <linux/slab.h> 19 #include <linux/i2c.h> 20 #include <linux/hwmon.h> 21 #include <linux/hwmon-sysfs.h> 22 #include <linux/jiffies.h> 23 24 /* Here are names of the chip's registers (a.k.a. commands) */ 25 enum ltc4215_cmd { 26 LTC4215_CONTROL = 0x00, /* rw */ 27 LTC4215_ALERT = 0x01, /* rw */ 28 LTC4215_STATUS = 0x02, /* ro */ 29 LTC4215_FAULT = 0x03, /* rw */ 30 LTC4215_SENSE = 0x04, /* rw */ 31 LTC4215_SOURCE = 0x05, /* rw */ 32 LTC4215_ADIN = 0x06, /* rw */ 33 }; 34 35 struct ltc4215_data { 36 struct i2c_client *client; 37 38 struct mutex update_lock; 39 bool valid; 40 unsigned long last_updated; /* in jiffies */ 41 42 /* Registers */ 43 u8 regs[7]; 44 }; 45 46 static struct ltc4215_data *ltc4215_update_device(struct device *dev) 47 { 48 struct ltc4215_data *data = dev_get_drvdata(dev); 49 struct i2c_client *client = data->client; 50 s32 val; 51 int i; 52 53 mutex_lock(&data->update_lock); 54 55 /* The chip's A/D updates 10 times per second */ 56 if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) { 57 58 dev_dbg(&client->dev, "Starting ltc4215 update\n"); 59 60 /* Read all registers */ 61 for (i = 0; i < ARRAY_SIZE(data->regs); i++) { 62 val = i2c_smbus_read_byte_data(client, i); 63 if (unlikely(val < 0)) 64 data->regs[i] = 0; 65 else 66 data->regs[i] = val; 67 } 68 69 data->last_updated = jiffies; 70 data->valid = 1; 71 } 72 73 mutex_unlock(&data->update_lock); 74 75 return data; 76 } 77 78 /* Return the voltage from the given register in millivolts */ 79 static int ltc4215_get_voltage(struct device *dev, u8 reg) 80 { 81 struct ltc4215_data *data = ltc4215_update_device(dev); 82 const u8 regval = data->regs[reg]; 83 u32 voltage = 0; 84 85 switch (reg) { 86 case LTC4215_SENSE: 87 /* 151 uV per increment */ 88 voltage = regval * 151 / 1000; 89 break; 90 case LTC4215_SOURCE: 91 /* 60.5 mV per increment */ 92 voltage = regval * 605 / 10; 93 break; 94 case LTC4215_ADIN: 95 /* 96 * The ADIN input is divided by 12.5, and has 4.82 mV 97 * per increment, so we have the additional multiply 98 */ 99 voltage = regval * 482 * 125 / 1000; 100 break; 101 default: 102 /* If we get here, the developer messed up */ 103 WARN_ON_ONCE(1); 104 break; 105 } 106 107 return voltage; 108 } 109 110 /* Return the current from the sense resistor in mA */ 111 static unsigned int ltc4215_get_current(struct device *dev) 112 { 113 struct ltc4215_data *data = ltc4215_update_device(dev); 114 115 /* 116 * The strange looking conversions that follow are fixed-point 117 * math, since we cannot do floating point in the kernel. 118 * 119 * Step 1: convert sense register to microVolts 120 * Step 2: convert voltage to milliAmperes 121 * 122 * If you play around with the V=IR equation, you come up with 123 * the following: X uV / Y mOhm == Z mA 124 * 125 * With the resistors that are fractions of a milliOhm, we multiply 126 * the voltage and resistance by 10, to shift the decimal point. 127 * Now we can use the normal division operator again. 128 */ 129 130 /* Calculate voltage in microVolts (151 uV per increment) */ 131 const unsigned int voltage = data->regs[LTC4215_SENSE] * 151; 132 133 /* Calculate current in milliAmperes (4 milliOhm sense resistor) */ 134 const unsigned int curr = voltage / 4; 135 136 return curr; 137 } 138 139 static ssize_t ltc4215_show_voltage(struct device *dev, 140 struct device_attribute *da, 141 char *buf) 142 { 143 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 144 const int voltage = ltc4215_get_voltage(dev, attr->index); 145 146 return snprintf(buf, PAGE_SIZE, "%d\n", voltage); 147 } 148 149 static ssize_t ltc4215_show_current(struct device *dev, 150 struct device_attribute *da, 151 char *buf) 152 { 153 const unsigned int curr = ltc4215_get_current(dev); 154 155 return snprintf(buf, PAGE_SIZE, "%u\n", curr); 156 } 157 158 static ssize_t ltc4215_show_power(struct device *dev, 159 struct device_attribute *da, 160 char *buf) 161 { 162 const unsigned int curr = ltc4215_get_current(dev); 163 const int output_voltage = ltc4215_get_voltage(dev, LTC4215_ADIN); 164 165 /* current in mA * voltage in mV == power in uW */ 166 const unsigned int power = abs(output_voltage * curr); 167 168 return snprintf(buf, PAGE_SIZE, "%u\n", power); 169 } 170 171 static ssize_t ltc4215_show_alarm(struct device *dev, 172 struct device_attribute *da, 173 char *buf) 174 { 175 struct sensor_device_attribute *attr = to_sensor_dev_attr(da); 176 struct ltc4215_data *data = ltc4215_update_device(dev); 177 const u8 reg = data->regs[LTC4215_STATUS]; 178 const u32 mask = attr->index; 179 180 return snprintf(buf, PAGE_SIZE, "%u\n", !!(reg & mask)); 181 } 182 183 /* 184 * These macros are used below in constructing device attribute objects 185 * for use with sysfs_create_group() to make a sysfs device file 186 * for each register. 187 */ 188 189 /* Construct a sensor_device_attribute structure for each register */ 190 191 /* Current */ 192 static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4215_show_current, NULL, 0); 193 static SENSOR_DEVICE_ATTR(curr1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 194 1 << 2); 195 196 /* Power (virtual) */ 197 static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ltc4215_show_power, NULL, 0); 198 199 /* Input Voltage */ 200 static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4215_show_voltage, NULL, 201 LTC4215_ADIN); 202 static SENSOR_DEVICE_ATTR(in1_max_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 203 1 << 0); 204 static SENSOR_DEVICE_ATTR(in1_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 205 1 << 1); 206 207 /* Output Voltage */ 208 static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4215_show_voltage, NULL, 209 LTC4215_SOURCE); 210 static SENSOR_DEVICE_ATTR(in2_min_alarm, S_IRUGO, ltc4215_show_alarm, NULL, 211 1 << 3); 212 213 /* 214 * Finally, construct an array of pointers to members of the above objects, 215 * as required for sysfs_create_group() 216 */ 217 static struct attribute *ltc4215_attrs[] = { 218 &sensor_dev_attr_curr1_input.dev_attr.attr, 219 &sensor_dev_attr_curr1_max_alarm.dev_attr.attr, 220 221 &sensor_dev_attr_power1_input.dev_attr.attr, 222 223 &sensor_dev_attr_in1_input.dev_attr.attr, 224 &sensor_dev_attr_in1_max_alarm.dev_attr.attr, 225 &sensor_dev_attr_in1_min_alarm.dev_attr.attr, 226 227 &sensor_dev_attr_in2_input.dev_attr.attr, 228 &sensor_dev_attr_in2_min_alarm.dev_attr.attr, 229 230 NULL, 231 }; 232 ATTRIBUTE_GROUPS(ltc4215); 233 234 static int ltc4215_probe(struct i2c_client *client, 235 const struct i2c_device_id *id) 236 { 237 struct i2c_adapter *adapter = client->adapter; 238 struct device *dev = &client->dev; 239 struct ltc4215_data *data; 240 struct device *hwmon_dev; 241 242 if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA)) 243 return -ENODEV; 244 245 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); 246 if (!data) 247 return -ENOMEM; 248 249 data->client = client; 250 mutex_init(&data->update_lock); 251 252 /* Initialize the LTC4215 chip */ 253 i2c_smbus_write_byte_data(client, LTC4215_FAULT, 0x00); 254 255 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, 256 data, 257 ltc4215_groups); 258 return PTR_ERR_OR_ZERO(hwmon_dev); 259 } 260 261 static const struct i2c_device_id ltc4215_id[] = { 262 { "ltc4215", 0 }, 263 { } 264 }; 265 MODULE_DEVICE_TABLE(i2c, ltc4215_id); 266 267 /* This is the driver that will be inserted */ 268 static struct i2c_driver ltc4215_driver = { 269 .driver = { 270 .name = "ltc4215", 271 }, 272 .probe = ltc4215_probe, 273 .id_table = ltc4215_id, 274 }; 275 276 module_i2c_driver(ltc4215_driver); 277 278 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>"); 279 MODULE_DESCRIPTION("LTC4215 driver"); 280 MODULE_LICENSE("GPL"); 281